From fb529ec8139b61c35d66d039b3c92512ca0cbbf3 Mon Sep 17 00:00:00 2001
From: Anthony Printup <92564080+anthonyprintup@users.noreply.github.com>
Date: Fri, 1 May 2026 20:54:06 +0200
Subject: [PATCH 1/5] fix: expose hosted string accessors as string_view

Emit immutable string field accessors as std::string_view when PROTOCYTE_ENABLE_STD_STRING_VIEW is enabled while preserving Span<const char> for default builds.

Simplify Span<char> conversion to construct std::string_view directly from data and size, treating null non-empty spans as a contract violation.

Regenerate checked smoke headers and add generator/smoke coverage for the hosted accessor surface.
---
 README.md                                     |  8 +--
 smoke/generated/compat.protocyte.hpp          | 22 ++++++++
 smoke/generated/example.protocyte.hpp         | 34 ++++++++++++
 smoke/generated/protocyte/runtime/runtime.hpp |  2 +-
 smoke/src/host_smoke.cpp                      | 17 ++++++
 src/protocyte/cpp.py                          | 54 +++++++++++++++----
 src/protocyte/runtime/runtime.hpp             |  2 +-
 tests/test_plugin.py                          | 20 ++++++-
 8 files changed, 143 insertions(+), 16 deletions(-)

diff --git a/README.md b/README.md
index 5fd4e6e..7bf80d9 100644
--- a/README.md
+++ b/README.md
@@ -450,9 +450,11 @@ target_compile_definitions(my_target PRIVATE PROTOCYTE_ENABLE_STD_STRING_VIEW=1)
 
 When `PROTOCYTE_ENABLE_STD_STRING_VIEW` is defined, the runtime includes
 `<string_view>` and both `::protocyte::Span<char>` / `Span<const char>` and
-`::protocyte::String` are implicitly convertible to `std::string_view`. The
-default accessor return type remains `Span<const char>`, so code that does not
-enable the option keeps the smaller no-exception surface.
+`::protocyte::String` are implicitly convertible to `std::string_view`.
+Generated immutable `string` field accessors also return `std::string_view`
+under this opt-in, so hosted code can pass string fields directly to
+standard-library APIs such as `std::format`. Code that does not enable the
+option keeps the smaller no-exception `Span<const char>` accessor surface.
 
 In a Windows kernel driver, one technically possible MSVC/STL-specific escape
 hatch is to provide the STL's internal out-of-range throw helper yourself so
diff --git a/smoke/generated/compat.protocyte.hpp b/smoke/generated/compat.protocyte.hpp
index 39032c4..bbd1202 100644
--- a/smoke/generated/compat.protocyte.hpp
+++ b/smoke/generated/compat.protocyte.hpp
@@ -5,6 +5,10 @@
 
 #include <protocyte/runtime/runtime.hpp>
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
 namespace protocyte_smoke::test::compat {
 
     enum struct EncodingMatrix_Mode : ::protocyte::i32 {
@@ -65,7 +69,11 @@ namespace protocyte_smoke::test::compat {
         }
         constexpr void clear_value() noexcept { value_ = {}; }
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view label() const noexcept { return label_.view(); }
+#else
         ::protocyte::Span<const char> label() const noexcept { return label_.view(); }
+#endif
         typename Config::String &mutable_label() noexcept { return label_; }
         template<class Value>::protocyte::Status set_label(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -652,7 +660,11 @@ namespace protocyte_smoke::test::compat {
         }
         constexpr void clear_f_double() noexcept { f_double_ = {}; }
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view f_string() const noexcept { return f_string_.view(); }
+#else
         ::protocyte::Span<const char> f_string() const noexcept { return f_string_.view(); }
+#endif
         typename Config::String &mutable_f_string() noexcept { return f_string_; }
         template<class Value>::protocyte::Status set_f_string(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -741,9 +753,15 @@ namespace protocyte_smoke::test::compat {
         constexpr bool has_oneof_string() const noexcept {
             return special_oneof_case_ == Special_oneofCase::oneof_string;
         }
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view oneof_string() const noexcept {
+            return has_oneof_string() ? special_oneof.oneof_string.view() : ::std::string_view {};
+        }
+#else
         ::protocyte::Span<const char> oneof_string() const noexcept {
             return has_oneof_string() ? special_oneof.oneof_string.view() : ::protocyte::Span<const char> {};
         }
+#endif
         template<class Value>::protocyte::Status set_oneof_string(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
         {
@@ -852,7 +870,11 @@ namespace protocyte_smoke::test::compat {
             has_opt_int32_ = false;
         }
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view opt_string() const noexcept { return opt_string_.view(); }
+#else
         ::protocyte::Span<const char> opt_string() const noexcept { return opt_string_.view(); }
+#endif
         bool has_opt_string() const noexcept { return has_opt_string_; }
         typename Config::String &mutable_opt_string() noexcept {
             has_opt_string_ = true;
diff --git a/smoke/generated/example.protocyte.hpp b/smoke/generated/example.protocyte.hpp
index 21b3f4c..043279a 100644
--- a/smoke/generated/example.protocyte.hpp
+++ b/smoke/generated/example.protocyte.hpp
@@ -96,7 +96,11 @@ namespace test::ultimate {
             return out;
         }
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view description() const noexcept { return description_.view(); }
+#else
         ::protocyte::Span<const char> description() const noexcept { return description_.view(); }
+#endif
         typename Config::String &mutable_description() noexcept { return description_; }
         template<class Value>::protocyte::Status set_description(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -394,7 +398,11 @@ namespace test::ultimate {
             return out;
         }
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view name() const noexcept { return name_.view(); }
+#else
         ::protocyte::Span<const char> name() const noexcept { return name_.view(); }
+#endif
         typename Config::String &mutable_name() noexcept { return name_; }
         template<class Value>::protocyte::Status set_name(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -1118,7 +1126,11 @@ namespace test::ultimate {
             deep_oneof_case_ = Deep_oneofCase::none;
         }
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view extreme() const noexcept { return extreme_.view(); }
+#else
         ::protocyte::Span<const char> extreme() const noexcept { return extreme_.view(); }
+#endif
         typename Config::String &mutable_extreme() noexcept { return extreme_; }
         template<class Value>::protocyte::Status set_extreme(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -1168,9 +1180,13 @@ namespace test::ultimate {
         }
 
         constexpr bool has_text() const noexcept { return deep_oneof_case_ == Deep_oneofCase::text; }
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view text() const noexcept { return has_text() ? deep_oneof.text.view() : ::std::string_view {}; }
+#else
         ::protocyte::Span<const char> text() const noexcept {
             return has_text() ? deep_oneof.text.view() : ::protocyte::Span<const char> {};
         }
+#endif
         template<class Value>::protocyte::Status set_text(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
         {
@@ -2297,7 +2313,11 @@ namespace test::ultimate {
         }
         constexpr void clear_f_bool() noexcept { f_bool_ = {}; }
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view f_string() const noexcept { return f_string_.view(); }
+#else
         ::protocyte::Span<const char> f_string() const noexcept { return f_string_.view(); }
+#endif
         typename Config::String &mutable_f_string() noexcept { return f_string_; }
         template<class Value>::protocyte::Status set_f_string(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -2399,9 +2419,15 @@ namespace test::ultimate {
         constexpr bool has_oneof_string() const noexcept {
             return special_oneof_case_ == Special_oneofCase::oneof_string;
         }
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view oneof_string() const noexcept {
+            return has_oneof_string() ? special_oneof.oneof_string.view() : ::std::string_view {};
+        }
+#else
         ::protocyte::Span<const char> oneof_string() const noexcept {
             return has_oneof_string() ? special_oneof.oneof_string.view() : ::protocyte::Span<const char> {};
         }
+#endif
         template<class Value>::protocyte::Status set_oneof_string(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
         {
@@ -2749,7 +2775,11 @@ namespace test::ultimate {
             has_opt_int32_ = false;
         }
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view opt_string() const noexcept { return opt_string_.view(); }
+#else
         ::protocyte::Span<const char> opt_string() const noexcept { return opt_string_.view(); }
+#endif
         bool has_opt_string() const noexcept { return has_opt_string_; }
         typename Config::String &mutable_opt_string() noexcept {
             has_opt_string_ = true;
@@ -6063,7 +6093,11 @@ namespace test::ultimate {
             return out;
         }
 
+#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+        ::std::string_view tag() const noexcept { return tag_.view(); }
+#else
         ::protocyte::Span<const char> tag() const noexcept { return tag_.view(); }
+#endif
         typename Config::String &mutable_tag() noexcept { return tag_; }
         template<class Value>::protocyte::Status set_tag(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
diff --git a/smoke/generated/protocyte/runtime/runtime.hpp b/smoke/generated/protocyte/runtime/runtime.hpp
index 6fb2585..314c868 100644
--- a/smoke/generated/protocyte/runtime/runtime.hpp
+++ b/smoke/generated/protocyte/runtime/runtime.hpp
@@ -1273,7 +1273,7 @@ namespace protocyte {
         constexpr operator ::std::string_view() const noexcept
             requires(::std::same_as<::std::remove_cv_t<T>, char>)
         {
-            return data_ == nullptr ? ::std::string_view {} : ::std::string_view {data_, size_};
+            return ::std::string_view {data_, size_};
         }
 #endif
         template<usize Count> constexpr Span<T, Count> first() const noexcept
diff --git a/smoke/src/host_smoke.cpp b/smoke/src/host_smoke.cpp
index bf8eef9..7fc0746 100644
--- a/smoke/src/host_smoke.cpp
+++ b/smoke/src/host_smoke.cpp
@@ -2,6 +2,9 @@
 #include <cstddef>
 #include <cstdint>
 #include <cstdlib>
+#if __has_include(<format>)
+#include <format>
+#endif
 #include <limits>
 #include <string>
 #include <string_view>
@@ -214,6 +217,16 @@ namespace {
         return protocyte::bytes_equal(lhs, rhs);
     }
 
+    template<class R, protocyte::usize RExtent>
+    bool view_equal(std::string_view lhs, protocyte::Span<R, RExtent> rhs) noexcept {
+        return view_equal(protocyte::Span<const char> {lhs.data(), lhs.size()}, rhs);
+    }
+
+    template<class L, protocyte::usize LExtent>
+    bool view_equal(protocyte::Span<L, LExtent> lhs, std::string_view rhs) noexcept {
+        return view_equal(lhs, protocyte::Span<const char> {rhs.data(), rhs.size()});
+    }
+
     template<size_t N> protocyte::Span<const protocyte::u8> view_of(const uint8_t (&data)[N]) noexcept {
         return protocyte::Span<const protocyte::u8> {data, N};
     }
@@ -2603,8 +2616,12 @@ TEST_CASE("byte setters accept contiguous byte containers", "[smoke][runtime][by
     const auto string_view = protocyte::byte_span_of(string_payload);
     REQUIRE(string_view);
     CHECK(view_equal(message.f_string(), *string_view));
+    static_assert(std::is_same_v<decltype(message.f_string()), std::string_view>);
     const std::string_view converted_span = message.f_string();
     CHECK(converted_span == std::string_view {"hello"});
+#if defined(__cpp_lib_format)
+    CHECK(std::format("{}", message.f_string()) == "hello");
+#endif
     const std::string_view converted_string = message.mutable_f_string();
     CHECK(converted_string == converted_span);
 
diff --git a/src/protocyte/cpp.py b/src/protocyte/cpp.py
index 0f5e236..2466119 100644
--- a/src/protocyte/cpp.py
+++ b/src/protocyte/cpp.py
@@ -211,6 +211,8 @@ def generate_header(file_model: FileModel, options: GeneratorOptions) -> str:
     extra_includes: list[str] = []
     if _file_uses_string_view(file_model):
         extra_includes.append("#include <string_view>")
+    elif _file_uses_std_string_view_accessors(file_model):
+        extra_includes.extend(["#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW", "#include <string_view>", "#endif"])
     for dependency in sorted(file_model.dependencies):
         extra_includes.append(f'#include "{_include_path(dependency, options)}"')
     if extra_includes:
@@ -813,11 +815,13 @@ def emit_setter_body() -> None:
         return
     if item.kind in {"string", "bytes"}:
         typ = _field_type(item, options)
-        view_type = "::protocyte::Span<const char>" if item.kind == "string" else "::protocyte::Span<const ::protocyte::u8>"
-        w.line(f"{view_type} {item.cpp_name}() const noexcept {{ return {_member(item)}.view(); }}")
-        if item.proto3_optional:
-            w.line(f"bool has_{item.cpp_name}() const noexcept {{ return has_{item.cpp_name}_; }}")
-        w.line(f"{typ}& mutable_{item.cpp_name}() noexcept {{")
+        if item.kind == "string":
+            _emit_string_view_accessor(w, item.cpp_name, f"{_member(item)}.view()")
+        else:
+            w.line(f"::protocyte::Span<const ::protocyte::u8> {item.cpp_name}() const noexcept {{ return {_member(item)}.view(); }}")
+        if item.proto3_optional:
+            w.line(f"bool has_{item.cpp_name}() const noexcept {{ return has_{item.cpp_name}_; }}")
+        w.line(f"{typ}& mutable_{item.cpp_name}() noexcept {{")
         w.push()
         if item.proto3_optional:
             w.line(f"has_{item.cpp_name}_ = true;")
@@ -879,10 +883,18 @@ def _emit_oneof_accessors(w: CppWriter, item: FieldModel, options: GeneratorOpti
         f"constexpr bool has_{item.cpp_name}() const noexcept {{ return {case_member} == {case_type}::{item.cpp_name}; }}"
     )
     if item.kind in {"string", "bytes"}:
-        view_type = "::protocyte::Span<const char>" if item.kind == "string" else "::protocyte::Span<const ::protocyte::u8>"
-        w.line(
-            f"{view_type} {item.cpp_name}() const noexcept {{ return has_{item.cpp_name}() ? {_member(item)}.view() : {view_type}{{}}; }}"
-        )
+        if item.kind == "string":
+            _emit_string_view_accessor(
+                w,
+                item.cpp_name,
+                f"has_{item.cpp_name}() ? {_member(item)}.view() : ::std::string_view{{}}",
+                f"has_{item.cpp_name}() ? {_member(item)}.view() : ::protocyte::Span<const char>{{}}",
+            )
+        else:
+            view_type = "::protocyte::Span<const ::protocyte::u8>"
+            w.line(
+                f"{view_type} {item.cpp_name}() const noexcept {{ return has_{item.cpp_name}() ? {_member(item)}.view() : {view_type}{{}}; }}"
+            )
         def emit_setter_body() -> None:
             if item.kind == "bytes" and item.array_enabled:
                 w.line(
@@ -1961,6 +1973,21 @@ def _runtime_scalar_type(cpp_type: str) -> str:
     return _RUNTIME_SCALAR_TYPES.get(cpp_type, cpp_type)
 
 
+def _emit_string_view_accessor(
+    w: CppWriter,
+    name: str,
+    string_view_expr: str,
+    span_expr: str | None = None,
+) -> None:
+    if span_expr is None:
+        span_expr = string_view_expr
+    w.line("#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW")
+    w.line(f"::std::string_view {name}() const noexcept {{ return {string_view_expr}; }}")
+    w.line("#else")
+    w.line(f"::protocyte::Span<const char> {name}() const noexcept {{ return {span_expr}; }}")
+    w.line("#endif")
+
+
 def _file_uses_string_view(file_model: FileModel) -> bool:
     if any(constant.kind == CONSTANT_KIND_STRING for constant in file_model.constants):
         return True
@@ -1970,6 +1997,15 @@ def _file_uses_string_view(file_model: FileModel) -> bool:
     return False
 
 
+def _file_uses_std_string_view_accessors(file_model: FileModel) -> bool:
+    for message in _walk_messages(file_model.messages):
+        if message.is_map_entry:
+            continue
+        if any(item.kind == "string" and not item.repeated for item in message.fields):
+            return True
+    return False
+
+
 def _ordered_messages(file_model: FileModel) -> list[MessageModel]:
     all_messages = [item for item in _walk_messages(file_model.messages) if not item.is_map_entry]
     by_name = {item.full_name: item for item in all_messages}
diff --git a/src/protocyte/runtime/runtime.hpp b/src/protocyte/runtime/runtime.hpp
index 6fb2585..314c868 100644
--- a/src/protocyte/runtime/runtime.hpp
+++ b/src/protocyte/runtime/runtime.hpp
@@ -1273,7 +1273,7 @@ namespace protocyte {
         constexpr operator ::std::string_view() const noexcept
             requires(::std::same_as<::std::remove_cv_t<T>, char>)
         {
-            return data_ == nullptr ? ::std::string_view {} : ::std::string_view {data_, size_};
+            return ::std::string_view {data_, size_};
         }
 #endif
         template<usize Count> constexpr Span<T, Count> first() const noexcept
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index f193a29..53ccadb 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -198,6 +198,8 @@ def test_runtime_byte_containers_use_bulk_copy_helpers() -> None:
     assert "copy_bytes(temp.data(), view.data(), view.size());" in bytes_body
     assert "constexpr operator ::std::string_view() const noexcept" in span_body
     assert "requires(::std::same_as<::std::remove_cv_t<T>, char>)" in span_body
+    assert "return ::std::string_view {data_, size_};" in span_body
+    assert "data_ == nullptr ? ::std::string_view {}" not in span_body
     assert "using value_type = const char;" in string_body
     assert "Span<const char> view() const noexcept" in string_body
     assert "Span<const u8> byte_view() const noexcept" in string_body
@@ -676,7 +678,14 @@ def test_generated_header_contains_expected_field_api() -> None:
 
     assert "namespace demo {" in header
     assert "bool has_opt_name() const noexcept" in header
-    assert "::protocyte::Span<const char> opt_name() const noexcept" in header
+    assert "#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n#include <string_view>\n#endif" in header
+    assert (
+        "  #ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
+        "  ::std::string_view opt_name() const noexcept { return opt_name_.view(); }\n"
+        "  #else\n"
+        "  ::protocyte::Span<const char> opt_name() const noexcept { return opt_name_.view(); }\n"
+        "  #endif"
+    ) in header
     assert "struct Sample {" in header
     assert "typename Config::template Map<typename Config::String, ::protocyte::i32> items_;" in header
     assert "typename Config::template Box<::demo::Sample<Config>> self_;" in header
@@ -1417,7 +1426,14 @@ def test_generated_header_emits_tagged_union_oneofs() -> None:
     assert "void clear_choice() noexcept {" in header
     assert "destroy_at_(&choice.text);" in header
     assert "destroy_at_(&choice.inner);" in header
-    assert "::protocyte::Span<const char> text() const noexcept" in header
+    assert "#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n#include <string_view>\n#endif" in header
+    assert (
+        "  #ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
+        "  ::std::string_view text() const noexcept { return has_text() ? choice.text.view() : ::std::string_view{}; }\n"
+        "  #else\n"
+        "  ::protocyte::Span<const char> text() const noexcept { return has_text() ? choice.text.view() : ::protocyte::Span<const char>{}; }\n"
+        "  #endif"
+    ) in header
     assert "union ChoiceStorage {" in header
     assert "ChoiceStorage() noexcept {}" in header
     assert "~ChoiceStorage() noexcept {}" in header

From 0da0b1195cdf51918b09358058158b0d64ccc15a Mon Sep 17 00:00:00 2001
From: Anthony Printup <92564080+anthonyprintup@users.noreply.github.com>
Date: Fri, 1 May 2026 21:18:52 +0200
Subject: [PATCH 2/5] fix: provide debug kernel string_view crt shims

Add smoke-driver-only fallback symbols for the MSVC debug STL CRT assertion hooks pulled in by std::string_view when PROTOCYTE_ENABLE_STD_STRING_VIEW is enabled.

Route unexpected shim calls through DbgPrintEx and KeBugCheckEx, and cover the guard with a source-level regression test.
---
 smoke/src/kernel_driver_smoke.cpp | 28 ++++++++++++++++++++++++++++
 tests/test_plugin.py              | 10 ++++++++++
 2 files changed, 38 insertions(+)

diff --git a/smoke/src/kernel_driver_smoke.cpp b/smoke/src/kernel_driver_smoke.cpp
index 5e422de..6f44f0a 100644
--- a/smoke/src/kernel_driver_smoke.cpp
+++ b/smoke/src/kernel_driver_smoke.cpp
@@ -24,6 +24,34 @@ void __cdecl operator delete[](void *ptr) noexcept { ::operator delete(ptr); }
 void __cdecl operator delete[](void *ptr, size_t) noexcept { ::operator delete(ptr); }
 #endif
 
+#if defined(PROTOCYTE_ENABLE_STD_STRING_VIEW) && defined(_DEBUG)
+// MSVC's debug STL imports these CRT assertion hooks through __imp_* data symbols.
+__declspec(noreturn) void protocyte_debug_crt_shim_bugcheck(const char *symbol_name) {
+    DbgPrintEx(DPFLTR_IHVDRIVER_ID, DPFLTR_ERROR_LEVEL,
+               "Protocyte kernel smoke: MSVC STL debug CRT fallback called for %s.\n", symbol_name);
+    KeBugCheckEx(MANUALLY_INITIATED_CRASH, 0x50535643u, 0u, 0u, 0u);
+    for (;;) {}
+}
+
+extern "C" __declspec(noreturn) void __cdecl protocyte_invoke_watson_shim(const wchar_t *, const wchar_t *,
+                                                                          const wchar_t *, unsigned int, uintptr_t) {
+    protocyte_debug_crt_shim_bugcheck("_invoke_watson");
+}
+
+extern "C" int __cdecl protocyte_crt_dbg_report_shim(int, const char *, int, const char *, const char *, ...) {
+    protocyte_debug_crt_shim_bugcheck("_CrtDbgReport");
+}
+
+using protocyte_invoke_watson_fn = void(__cdecl *)(const wchar_t *, const wchar_t *, const wchar_t *, unsigned int,
+                                                   uintptr_t);
+using protocyte_crt_dbg_report_fn = int(__cdecl *)(int, const char *, int, const char *, const char *, ...);
+
+extern "C" {
+    protocyte_invoke_watson_fn __imp__invoke_watson = &protocyte_invoke_watson_shim;
+    protocyte_crt_dbg_report_fn __imp__CrtDbgReport = &protocyte_crt_dbg_report_shim;
+}
+#endif
+
 namespace {
 
     constexpr ULONG protocyte_pool_tag = 'TyCP';
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index 53ccadb..e1a783e 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -53,6 +53,16 @@ def test_runtime_rejects_unmatched_end_group_in_skip_field() -> None:
     assert "case WireType::EGROUP: return {};" not in runtime_header
 
 
+def test_kernel_smoke_provides_debug_string_view_crt_shims() -> None:
+    source = (Path(__file__).resolve().parents[1] / "smoke" / "src" / "kernel_driver_smoke.cpp").read_text()
+
+    assert "#if defined(PROTOCYTE_ENABLE_STD_STRING_VIEW) && defined(_DEBUG)" in source
+    assert "__imp__invoke_watson" in source
+    assert "__imp__CrtDbgReport" in source
+    assert "DbgPrintEx" in source
+    assert "KeBugCheckEx" in source
+
+
 def test_runtime_container_growth_checks_capacity_limits() -> None:
     runtime_header = runtime_files()["protocyte/runtime/runtime.hpp"]
 

From f8c4539e3c36edafd2a3315e86fb975430559a5d Mon Sep 17 00:00:00 2001
From: Anthony Printup <92564080+anthonyprintup@users.noreply.github.com>
Date: Fri, 1 May 2026 21:43:32 +0200
Subject: [PATCH 3/5] fix: avoid redundant generated string_view includes

Rely on the runtime header for PROTOCYTE_ENABLE_STD_STRING_VIEW accessor support instead of emitting a guarded string_view include from generated message headers.

Keep string-constant headers self-contained when the opt-in macro is off by emitting string_view only under the inverse guard, and update checked smoke outputs.
---
 smoke/generated/compat.protocyte.hpp        |  4 ----
 smoke/generated/cross_package.protocyte.hpp |  2 ++
 smoke/generated/example.protocyte.hpp       |  2 ++
 src/protocyte/cpp.py                        | 13 +------------
 tests/test_plugin.py                        | 20 ++++++++++++++------
 5 files changed, 19 insertions(+), 22 deletions(-)

diff --git a/smoke/generated/compat.protocyte.hpp b/smoke/generated/compat.protocyte.hpp
index bbd1202..ad29399 100644
--- a/smoke/generated/compat.protocyte.hpp
+++ b/smoke/generated/compat.protocyte.hpp
@@ -5,10 +5,6 @@
 
 #include <protocyte/runtime/runtime.hpp>
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
-#include <string_view>
-#endif
-
 namespace protocyte_smoke::test::compat {
 
     enum struct EncodingMatrix_Mode : ::protocyte::i32 {
diff --git a/smoke/generated/cross_package.protocyte.hpp b/smoke/generated/cross_package.protocyte.hpp
index a4d9029..ed1cc9b 100644
--- a/smoke/generated/cross_package.protocyte.hpp
+++ b/smoke/generated/cross_package.protocyte.hpp
@@ -5,7 +5,9 @@
 
 #include <protocyte/runtime/runtime.hpp>
 
+#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW
 #include <string_view>
+#endif
 
 namespace test::crosspkg {
 
diff --git a/smoke/generated/example.protocyte.hpp b/smoke/generated/example.protocyte.hpp
index 043279a..1e48a15 100644
--- a/smoke/generated/example.protocyte.hpp
+++ b/smoke/generated/example.protocyte.hpp
@@ -5,7 +5,9 @@
 
 #include <protocyte/runtime/runtime.hpp>
 
+#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW
 #include <string_view>
+#endif
 
 namespace test::ultimate {
 
diff --git a/src/protocyte/cpp.py b/src/protocyte/cpp.py
index 2466119..14a5047 100644
--- a/src/protocyte/cpp.py
+++ b/src/protocyte/cpp.py
@@ -210,9 +210,7 @@ def generate_header(file_model: FileModel, options: GeneratorOptions) -> str:
     w.line(f"#include <{options.runtime_prefix}/runtime.hpp>")
     extra_includes: list[str] = []
     if _file_uses_string_view(file_model):
-        extra_includes.append("#include <string_view>")
-    elif _file_uses_std_string_view_accessors(file_model):
-        extra_includes.extend(["#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW", "#include <string_view>", "#endif"])
+        extra_includes.extend(["#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW", "#include <string_view>", "#endif"])
     for dependency in sorted(file_model.dependencies):
         extra_includes.append(f'#include "{_include_path(dependency, options)}"')
     if extra_includes:
@@ -1997,15 +1995,6 @@ def _file_uses_string_view(file_model: FileModel) -> bool:
     return False
 
 
-def _file_uses_std_string_view_accessors(file_model: FileModel) -> bool:
-    for message in _walk_messages(file_model.messages):
-        if message.is_map_entry:
-            continue
-        if any(item.kind == "string" and not item.repeated for item in message.fields):
-            return True
-    return False
-
-
 def _ordered_messages(file_model: FileModel) -> list[MessageModel]:
     all_messages = [item for item in _walk_messages(file_model.messages) if not item.is_map_entry]
     by_name = {item.full_name: item for item in all_messages}
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index e1a783e..66d5e2e 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -688,7 +688,7 @@ def test_generated_header_contains_expected_field_api() -> None:
 
     assert "namespace demo {" in header
     assert "bool has_opt_name() const noexcept" in header
-    assert "#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n#include <string_view>\n#endif" in header
+    assert "#include <string_view>" not in header
     assert (
         "  #ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
         "  ::std::string_view opt_name() const noexcept { return opt_name_.view(); }\n"
@@ -1056,8 +1056,12 @@ def test_generated_header_emits_constants_and_array_storage() -> None:
     header = files["arrays.protocyte.hpp"]
     runtime_header = files["protocyte/runtime/runtime.hpp"]
 
-    assert '#include <protocyte/runtime/runtime.hpp>\n\n#include <string_view>' in header
-    assert "#include <string_view>" in header
+    assert (
+        "#include <protocyte/runtime/runtime.hpp>\n\n"
+        "#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
+        "#include <string_view>\n"
+        "#endif"
+    ) in header
     assert "inline constexpr ::protocyte::u32 FILE_CAP {16u};" in header
     assert 'inline constexpr ::std::string_view FILE_LABEL {"ell", 3u};' in header
     assert "inline constexpr bool FILE_READY {true};" in header
@@ -1391,8 +1395,12 @@ def test_generated_header_emits_utf8_string_constants() -> None:
 
     assert not response.error
     header = next(file.content for file in response.file if file.name == "unicode.protocyte.hpp")
-    assert '#include <protocyte/runtime/runtime.hpp>\n\n#include <string_view>' in header
-    assert '#include <string_view>' in header
+    assert (
+        "#include <protocyte/runtime/runtime.hpp>\n\n"
+        "#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
+        "#include <string_view>\n"
+        "#endif"
+    ) in header
     assert 'static constexpr ::std::string_view NAME {"\\xc4"' in header
     assert '"\\x80"' in header
     assert '"\\xc3"' in header
@@ -1436,7 +1444,7 @@ def test_generated_header_emits_tagged_union_oneofs() -> None:
     assert "void clear_choice() noexcept {" in header
     assert "destroy_at_(&choice.text);" in header
     assert "destroy_at_(&choice.inner);" in header
-    assert "#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n#include <string_view>\n#endif" in header
+    assert "#include <string_view>" not in header
     assert (
         "  #ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
         "  ::std::string_view text() const noexcept { return has_text() ? choice.text.view() : ::std::string_view{}; }\n"

From b0852b57232eca19e62879834bb98f773ca3bed6 Mon Sep 17 00:00:00 2001
From: Anthony Printup <92564080+anthonyprintup@users.noreply.github.com>
Date: Fri, 1 May 2026 21:56:05 +0200
Subject: [PATCH 4/5] fix: honor disabled string view macro value

Switch PROTOCYTE_ENABLE_STD_STRING_VIEW guards from definedness checks to value checks so -DPROTOCYTE_ENABLE_STD_STRING_VIEW=0 uses the non-string_view accessor path.

Update inverse generated string constant includes, kernel smoke guards, documentation, tests, and regenerated smoke outputs.
---
 README.md                                     | 10 +++++-----
 smoke/generated/compat.protocyte.hpp          |  8 ++++----
 smoke/generated/cross_package.protocyte.hpp   |  2 +-
 smoke/generated/example.protocyte.hpp         | 18 +++++++++---------
 smoke/generated/protocyte/runtime/runtime.hpp |  6 +++---
 smoke/src/kernel_driver_smoke.cpp             |  2 +-
 src/protocyte/cpp.py                          |  4 ++--
 src/protocyte/runtime/runtime.hpp             |  6 +++---
 tests/test_plugin.py                          | 13 +++++++------
 9 files changed, 35 insertions(+), 34 deletions(-)

diff --git a/README.md b/README.md
index 7bf80d9..e070100 100644
--- a/README.md
+++ b/README.md
@@ -448,11 +448,11 @@ Hosted users who want standard-library interoperability can opt in:
 target_compile_definitions(my_target PRIVATE PROTOCYTE_ENABLE_STD_STRING_VIEW=1)
 ```
 
-When `PROTOCYTE_ENABLE_STD_STRING_VIEW` is defined, the runtime includes
-`<string_view>` and both `::protocyte::Span<char>` / `Span<const char>` and
-`::protocyte::String` are implicitly convertible to `std::string_view`.
-Generated immutable `string` field accessors also return `std::string_view`
-under this opt-in, so hosted code can pass string fields directly to
+When `PROTOCYTE_ENABLE_STD_STRING_VIEW` is set to a nonzero value, the runtime
+includes `<string_view>` and both `::protocyte::Span<char>` / `Span<const char>`
+and `::protocyte::String` are implicitly convertible to `std::string_view`.
+Generated immutable `string` field accessors also return `std::string_view` under
+this opt-in, so hosted code can pass string fields directly to
 standard-library APIs such as `std::format`. Code that does not enable the
 option keeps the smaller no-exception `Span<const char>` accessor surface.
 
diff --git a/smoke/generated/compat.protocyte.hpp b/smoke/generated/compat.protocyte.hpp
index ad29399..10bd441 100644
--- a/smoke/generated/compat.protocyte.hpp
+++ b/smoke/generated/compat.protocyte.hpp
@@ -65,7 +65,7 @@ namespace protocyte_smoke::test::compat {
         }
         constexpr void clear_value() noexcept { value_ = {}; }
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view label() const noexcept { return label_.view(); }
 #else
         ::protocyte::Span<const char> label() const noexcept { return label_.view(); }
@@ -656,7 +656,7 @@ namespace protocyte_smoke::test::compat {
         }
         constexpr void clear_f_double() noexcept { f_double_ = {}; }
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view f_string() const noexcept { return f_string_.view(); }
 #else
         ::protocyte::Span<const char> f_string() const noexcept { return f_string_.view(); }
@@ -749,7 +749,7 @@ namespace protocyte_smoke::test::compat {
         constexpr bool has_oneof_string() const noexcept {
             return special_oneof_case_ == Special_oneofCase::oneof_string;
         }
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view oneof_string() const noexcept {
             return has_oneof_string() ? special_oneof.oneof_string.view() : ::std::string_view {};
         }
@@ -866,7 +866,7 @@ namespace protocyte_smoke::test::compat {
             has_opt_int32_ = false;
         }
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view opt_string() const noexcept { return opt_string_.view(); }
 #else
         ::protocyte::Span<const char> opt_string() const noexcept { return opt_string_.view(); }
diff --git a/smoke/generated/cross_package.protocyte.hpp b/smoke/generated/cross_package.protocyte.hpp
index ed1cc9b..a4ca8fd 100644
--- a/smoke/generated/cross_package.protocyte.hpp
+++ b/smoke/generated/cross_package.protocyte.hpp
@@ -5,7 +5,7 @@
 
 #include <protocyte/runtime/runtime.hpp>
 
-#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if !PROTOCYTE_ENABLE_STD_STRING_VIEW
 #include <string_view>
 #endif
 
diff --git a/smoke/generated/example.protocyte.hpp b/smoke/generated/example.protocyte.hpp
index 1e48a15..762750d 100644
--- a/smoke/generated/example.protocyte.hpp
+++ b/smoke/generated/example.protocyte.hpp
@@ -5,7 +5,7 @@
 
 #include <protocyte/runtime/runtime.hpp>
 
-#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if !PROTOCYTE_ENABLE_STD_STRING_VIEW
 #include <string_view>
 #endif
 
@@ -98,7 +98,7 @@ namespace test::ultimate {
             return out;
         }
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view description() const noexcept { return description_.view(); }
 #else
         ::protocyte::Span<const char> description() const noexcept { return description_.view(); }
@@ -400,7 +400,7 @@ namespace test::ultimate {
             return out;
         }
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view name() const noexcept { return name_.view(); }
 #else
         ::protocyte::Span<const char> name() const noexcept { return name_.view(); }
@@ -1128,7 +1128,7 @@ namespace test::ultimate {
             deep_oneof_case_ = Deep_oneofCase::none;
         }
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view extreme() const noexcept { return extreme_.view(); }
 #else
         ::protocyte::Span<const char> extreme() const noexcept { return extreme_.view(); }
@@ -1182,7 +1182,7 @@ namespace test::ultimate {
         }
 
         constexpr bool has_text() const noexcept { return deep_oneof_case_ == Deep_oneofCase::text; }
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view text() const noexcept { return has_text() ? deep_oneof.text.view() : ::std::string_view {}; }
 #else
         ::protocyte::Span<const char> text() const noexcept {
@@ -2315,7 +2315,7 @@ namespace test::ultimate {
         }
         constexpr void clear_f_bool() noexcept { f_bool_ = {}; }
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view f_string() const noexcept { return f_string_.view(); }
 #else
         ::protocyte::Span<const char> f_string() const noexcept { return f_string_.view(); }
@@ -2421,7 +2421,7 @@ namespace test::ultimate {
         constexpr bool has_oneof_string() const noexcept {
             return special_oneof_case_ == Special_oneofCase::oneof_string;
         }
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view oneof_string() const noexcept {
             return has_oneof_string() ? special_oneof.oneof_string.view() : ::std::string_view {};
         }
@@ -2777,7 +2777,7 @@ namespace test::ultimate {
             has_opt_int32_ = false;
         }
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view opt_string() const noexcept { return opt_string_.view(); }
 #else
         ::protocyte::Span<const char> opt_string() const noexcept { return opt_string_.view(); }
@@ -6095,7 +6095,7 @@ namespace test::ultimate {
             return out;
         }
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         ::std::string_view tag() const noexcept { return tag_.view(); }
 #else
         ::protocyte::Span<const char> tag() const noexcept { return tag_.view(); }
diff --git a/smoke/generated/protocyte/runtime/runtime.hpp b/smoke/generated/protocyte/runtime/runtime.hpp
index 314c868..d1ecf12 100644
--- a/smoke/generated/protocyte/runtime/runtime.hpp
+++ b/smoke/generated/protocyte/runtime/runtime.hpp
@@ -11,7 +11,7 @@
 #include <new>
 #include <type_traits>
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
 #include <string_view>
 #endif
 
@@ -1269,7 +1269,7 @@ namespace protocyte {
         constexpr usize size() const noexcept { return size_; }
         constexpr usize size_bytes() const noexcept { return size_ * sizeof(T); }
         constexpr bool empty() const noexcept { return size_ == 0u; }
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         constexpr operator ::std::string_view() const noexcept
             requires(::std::same_as<::std::remove_cv_t<T>, char>)
         {
@@ -2869,7 +2869,7 @@ namespace protocyte {
         usize size() const noexcept { return bytes_.size(); }
         usize length() const noexcept { return size(); }
         bool empty() const noexcept { return bytes_.empty(); }
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         operator ::std::string_view() const noexcept { return view(); }
 #endif
         void clear() noexcept { bytes_.clear(); }
diff --git a/smoke/src/kernel_driver_smoke.cpp b/smoke/src/kernel_driver_smoke.cpp
index 6f44f0a..db5523c 100644
--- a/smoke/src/kernel_driver_smoke.cpp
+++ b/smoke/src/kernel_driver_smoke.cpp
@@ -24,7 +24,7 @@ void __cdecl operator delete[](void *ptr) noexcept { ::operator delete(ptr); }
 void __cdecl operator delete[](void *ptr, size_t) noexcept { ::operator delete(ptr); }
 #endif
 
-#if defined(PROTOCYTE_ENABLE_STD_STRING_VIEW) && defined(_DEBUG)
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW && defined(_DEBUG)
 // MSVC's debug STL imports these CRT assertion hooks through __imp_* data symbols.
 __declspec(noreturn) void protocyte_debug_crt_shim_bugcheck(const char *symbol_name) {
     DbgPrintEx(DPFLTR_IHVDRIVER_ID, DPFLTR_ERROR_LEVEL,
diff --git a/src/protocyte/cpp.py b/src/protocyte/cpp.py
index 14a5047..3cfe558 100644
--- a/src/protocyte/cpp.py
+++ b/src/protocyte/cpp.py
@@ -210,7 +210,7 @@ def generate_header(file_model: FileModel, options: GeneratorOptions) -> str:
     w.line(f"#include <{options.runtime_prefix}/runtime.hpp>")
     extra_includes: list[str] = []
     if _file_uses_string_view(file_model):
-        extra_includes.extend(["#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW", "#include <string_view>", "#endif"])
+        extra_includes.extend(["#if !PROTOCYTE_ENABLE_STD_STRING_VIEW", "#include <string_view>", "#endif"])
     for dependency in sorted(file_model.dependencies):
         extra_includes.append(f'#include "{_include_path(dependency, options)}"')
     if extra_includes:
@@ -1979,7 +1979,7 @@ def _emit_string_view_accessor(
 ) -> None:
     if span_expr is None:
         span_expr = string_view_expr
-    w.line("#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW")
+    w.line("#if PROTOCYTE_ENABLE_STD_STRING_VIEW")
     w.line(f"::std::string_view {name}() const noexcept {{ return {string_view_expr}; }}")
     w.line("#else")
     w.line(f"::protocyte::Span<const char> {name}() const noexcept {{ return {span_expr}; }}")
diff --git a/src/protocyte/runtime/runtime.hpp b/src/protocyte/runtime/runtime.hpp
index 314c868..d1ecf12 100644
--- a/src/protocyte/runtime/runtime.hpp
+++ b/src/protocyte/runtime/runtime.hpp
@@ -11,7 +11,7 @@
 #include <new>
 #include <type_traits>
 
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
 #include <string_view>
 #endif
 
@@ -1269,7 +1269,7 @@ namespace protocyte {
         constexpr usize size() const noexcept { return size_; }
         constexpr usize size_bytes() const noexcept { return size_ * sizeof(T); }
         constexpr bool empty() const noexcept { return size_ == 0u; }
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         constexpr operator ::std::string_view() const noexcept
             requires(::std::same_as<::std::remove_cv_t<T>, char>)
         {
@@ -2869,7 +2869,7 @@ namespace protocyte {
         usize size() const noexcept { return bytes_.size(); }
         usize length() const noexcept { return size(); }
         bool empty() const noexcept { return bytes_.empty(); }
-#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
         operator ::std::string_view() const noexcept { return view(); }
 #endif
         void clear() noexcept { bytes_.clear(); }
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index 66d5e2e..9413529 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -56,7 +56,7 @@ def test_runtime_rejects_unmatched_end_group_in_skip_field() -> None:
 def test_kernel_smoke_provides_debug_string_view_crt_shims() -> None:
     source = (Path(__file__).resolve().parents[1] / "smoke" / "src" / "kernel_driver_smoke.cpp").read_text()
 
-    assert "#if defined(PROTOCYTE_ENABLE_STD_STRING_VIEW) && defined(_DEBUG)" in source
+    assert "#if PROTOCYTE_ENABLE_STD_STRING_VIEW && defined(_DEBUG)" in source
     assert "__imp__invoke_watson" in source
     assert "__imp__CrtDbgReport" in source
     assert "DbgPrintEx" in source
@@ -183,7 +183,8 @@ def test_runtime_byte_containers_use_bulk_copy_helpers() -> None:
     )[0]
 
     assert "#include <cstring>" in runtime_header
-    assert "#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n#include <string_view>\n#endif" in runtime_header
+    assert "#if PROTOCYTE_ENABLE_STD_STRING_VIEW\n#include <string_view>\n#endif" in runtime_header
+    assert "#ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW" not in runtime_header
     assert "inline void copy_bytes(u8 *dst, const u8 *src, const usize count) noexcept" in runtime_header
     assert "if (!count || dst == src)" in runtime_header
     assert "::std::memmove(dst, src, count);" in runtime_header
@@ -690,7 +691,7 @@ def test_generated_header_contains_expected_field_api() -> None:
     assert "bool has_opt_name() const noexcept" in header
     assert "#include <string_view>" not in header
     assert (
-        "  #ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
+        "  #if PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
         "  ::std::string_view opt_name() const noexcept { return opt_name_.view(); }\n"
         "  #else\n"
         "  ::protocyte::Span<const char> opt_name() const noexcept { return opt_name_.view(); }\n"
@@ -1058,7 +1059,7 @@ def test_generated_header_emits_constants_and_array_storage() -> None:
 
     assert (
         "#include <protocyte/runtime/runtime.hpp>\n\n"
-        "#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
+        "#if !PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
         "#include <string_view>\n"
         "#endif"
     ) in header
@@ -1397,7 +1398,7 @@ def test_generated_header_emits_utf8_string_constants() -> None:
     header = next(file.content for file in response.file if file.name == "unicode.protocyte.hpp")
     assert (
         "#include <protocyte/runtime/runtime.hpp>\n\n"
-        "#ifndef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
+        "#if !PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
         "#include <string_view>\n"
         "#endif"
     ) in header
@@ -1446,7 +1447,7 @@ def test_generated_header_emits_tagged_union_oneofs() -> None:
     assert "destroy_at_(&choice.inner);" in header
     assert "#include <string_view>" not in header
     assert (
-        "  #ifdef PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
+        "  #if PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
         "  ::std::string_view text() const noexcept { return has_text() ? choice.text.view() : ::std::string_view{}; }\n"
         "  #else\n"
         "  ::protocyte::Span<const char> text() const noexcept { return has_text() ? choice.text.view() : ::protocyte::Span<const char>{}; }\n"

From 4610bafa1554cedeee7aa3eab5dada2a22ed2db1 Mon Sep 17 00:00:00 2001
From: Anthony Printup <92564080+anthonyprintup@users.noreply.github.com>
Date: Fri, 1 May 2026 22:09:24 +0200
Subject: [PATCH 5/5] refactor: alias generated string view return type

Add protocyte::StringView as the runtime-selected string view type.

Use the alias in generated immutable string accessors so string and oneof bodies are no longer duplicated across the string_view feature branch.

Regenerate smoke checked outputs and update generator assertions.
---
 smoke/generated/compat.protocyte.hpp          | 28 ++--------
 smoke/generated/example.protocyte.hpp         | 54 ++++---------------
 smoke/generated/protocyte/runtime/runtime.hpp |  6 +++
 src/protocyte/cpp.py                          | 14 ++---
 src/protocyte/runtime/runtime.hpp             |  6 +++
 tests/test_plugin.py                          | 20 +++----
 6 files changed, 38 insertions(+), 90 deletions(-)

diff --git a/smoke/generated/compat.protocyte.hpp b/smoke/generated/compat.protocyte.hpp
index 10bd441..e5ffda6 100644
--- a/smoke/generated/compat.protocyte.hpp
+++ b/smoke/generated/compat.protocyte.hpp
@@ -65,11 +65,7 @@ namespace protocyte_smoke::test::compat {
         }
         constexpr void clear_value() noexcept { value_ = {}; }
 
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view label() const noexcept { return label_.view(); }
-#else
-        ::protocyte::Span<const char> label() const noexcept { return label_.view(); }
-#endif
+        ::protocyte::StringView label() const noexcept { return label_.view(); }
         typename Config::String &mutable_label() noexcept { return label_; }
         template<class Value>::protocyte::Status set_label(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -656,11 +652,7 @@ namespace protocyte_smoke::test::compat {
         }
         constexpr void clear_f_double() noexcept { f_double_ = {}; }
 
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view f_string() const noexcept { return f_string_.view(); }
-#else
-        ::protocyte::Span<const char> f_string() const noexcept { return f_string_.view(); }
-#endif
+        ::protocyte::StringView f_string() const noexcept { return f_string_.view(); }
         typename Config::String &mutable_f_string() noexcept { return f_string_; }
         template<class Value>::protocyte::Status set_f_string(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -749,15 +741,9 @@ namespace protocyte_smoke::test::compat {
         constexpr bool has_oneof_string() const noexcept {
             return special_oneof_case_ == Special_oneofCase::oneof_string;
         }
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view oneof_string() const noexcept {
-            return has_oneof_string() ? special_oneof.oneof_string.view() : ::std::string_view {};
+        ::protocyte::StringView oneof_string() const noexcept {
+            return has_oneof_string() ? special_oneof.oneof_string.view() : ::protocyte::StringView {};
         }
-#else
-        ::protocyte::Span<const char> oneof_string() const noexcept {
-            return has_oneof_string() ? special_oneof.oneof_string.view() : ::protocyte::Span<const char> {};
-        }
-#endif
         template<class Value>::protocyte::Status set_oneof_string(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
         {
@@ -866,11 +852,7 @@ namespace protocyte_smoke::test::compat {
             has_opt_int32_ = false;
         }
 
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view opt_string() const noexcept { return opt_string_.view(); }
-#else
-        ::protocyte::Span<const char> opt_string() const noexcept { return opt_string_.view(); }
-#endif
+        ::protocyte::StringView opt_string() const noexcept { return opt_string_.view(); }
         bool has_opt_string() const noexcept { return has_opt_string_; }
         typename Config::String &mutable_opt_string() noexcept {
             has_opt_string_ = true;
diff --git a/smoke/generated/example.protocyte.hpp b/smoke/generated/example.protocyte.hpp
index 762750d..05e9b0c 100644
--- a/smoke/generated/example.protocyte.hpp
+++ b/smoke/generated/example.protocyte.hpp
@@ -98,11 +98,7 @@ namespace test::ultimate {
             return out;
         }
 
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view description() const noexcept { return description_.view(); }
-#else
-        ::protocyte::Span<const char> description() const noexcept { return description_.view(); }
-#endif
+        ::protocyte::StringView description() const noexcept { return description_.view(); }
         typename Config::String &mutable_description() noexcept { return description_; }
         template<class Value>::protocyte::Status set_description(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -400,11 +396,7 @@ namespace test::ultimate {
             return out;
         }
 
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view name() const noexcept { return name_.view(); }
-#else
-        ::protocyte::Span<const char> name() const noexcept { return name_.view(); }
-#endif
+        ::protocyte::StringView name() const noexcept { return name_.view(); }
         typename Config::String &mutable_name() noexcept { return name_; }
         template<class Value>::protocyte::Status set_name(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -1128,11 +1120,7 @@ namespace test::ultimate {
             deep_oneof_case_ = Deep_oneofCase::none;
         }
 
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view extreme() const noexcept { return extreme_.view(); }
-#else
-        ::protocyte::Span<const char> extreme() const noexcept { return extreme_.view(); }
-#endif
+        ::protocyte::StringView extreme() const noexcept { return extreme_.view(); }
         typename Config::String &mutable_extreme() noexcept { return extreme_; }
         template<class Value>::protocyte::Status set_extreme(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -1182,13 +1170,9 @@ namespace test::ultimate {
         }
 
         constexpr bool has_text() const noexcept { return deep_oneof_case_ == Deep_oneofCase::text; }
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view text() const noexcept { return has_text() ? deep_oneof.text.view() : ::std::string_view {}; }
-#else
-        ::protocyte::Span<const char> text() const noexcept {
-            return has_text() ? deep_oneof.text.view() : ::protocyte::Span<const char> {};
+        ::protocyte::StringView text() const noexcept {
+            return has_text() ? deep_oneof.text.view() : ::protocyte::StringView {};
         }
-#endif
         template<class Value>::protocyte::Status set_text(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
         {
@@ -2315,11 +2299,7 @@ namespace test::ultimate {
         }
         constexpr void clear_f_bool() noexcept { f_bool_ = {}; }
 
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view f_string() const noexcept { return f_string_.view(); }
-#else
-        ::protocyte::Span<const char> f_string() const noexcept { return f_string_.view(); }
-#endif
+        ::protocyte::StringView f_string() const noexcept { return f_string_.view(); }
         typename Config::String &mutable_f_string() noexcept { return f_string_; }
         template<class Value>::protocyte::Status set_f_string(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
@@ -2421,15 +2401,9 @@ namespace test::ultimate {
         constexpr bool has_oneof_string() const noexcept {
             return special_oneof_case_ == Special_oneofCase::oneof_string;
         }
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view oneof_string() const noexcept {
-            return has_oneof_string() ? special_oneof.oneof_string.view() : ::std::string_view {};
+        ::protocyte::StringView oneof_string() const noexcept {
+            return has_oneof_string() ? special_oneof.oneof_string.view() : ::protocyte::StringView {};
         }
-#else
-        ::protocyte::Span<const char> oneof_string() const noexcept {
-            return has_oneof_string() ? special_oneof.oneof_string.view() : ::protocyte::Span<const char> {};
-        }
-#endif
         template<class Value>::protocyte::Status set_oneof_string(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
         {
@@ -2777,11 +2751,7 @@ namespace test::ultimate {
             has_opt_int32_ = false;
         }
 
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view opt_string() const noexcept { return opt_string_.view(); }
-#else
-        ::protocyte::Span<const char> opt_string() const noexcept { return opt_string_.view(); }
-#endif
+        ::protocyte::StringView opt_string() const noexcept { return opt_string_.view(); }
         bool has_opt_string() const noexcept { return has_opt_string_; }
         typename Config::String &mutable_opt_string() noexcept {
             has_opt_string_ = true;
@@ -6095,11 +6065,7 @@ namespace test::ultimate {
             return out;
         }
 
-#if PROTOCYTE_ENABLE_STD_STRING_VIEW
-        ::std::string_view tag() const noexcept { return tag_.view(); }
-#else
-        ::protocyte::Span<const char> tag() const noexcept { return tag_.view(); }
-#endif
+        ::protocyte::StringView tag() const noexcept { return tag_.view(); }
         typename Config::String &mutable_tag() noexcept { return tag_; }
         template<class Value>::protocyte::Status set_tag(const Value &value) noexcept
             requires(::protocyte::ByteSpanSource<Value> && !::protocyte::TextSource<Value>)
diff --git a/smoke/generated/protocyte/runtime/runtime.hpp b/smoke/generated/protocyte/runtime/runtime.hpp
index d1ecf12..187b041 100644
--- a/smoke/generated/protocyte/runtime/runtime.hpp
+++ b/smoke/generated/protocyte/runtime/runtime.hpp
@@ -1316,6 +1316,12 @@ namespace protocyte {
         requires(!DataSizeSpanSource<Range &> && PointerSpanSource<Range &>)
     Span(Range &) -> Span<::std::remove_pointer_t<SpanBeginPointer<Range &>>>;
 
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
+    using StringView = ::std::string_view;
+#else
+    using StringView = Span<const char>;
+#endif
+
     template<class T>
     concept SpanSource = requires(T &value) { Span {value}; } || requires(const T &value) { Span {value}; };
 
diff --git a/src/protocyte/cpp.py b/src/protocyte/cpp.py
index 3cfe558..9c6e345 100644
--- a/src/protocyte/cpp.py
+++ b/src/protocyte/cpp.py
@@ -885,8 +885,7 @@ def _emit_oneof_accessors(w: CppWriter, item: FieldModel, options: GeneratorOpti
             _emit_string_view_accessor(
                 w,
                 item.cpp_name,
-                f"has_{item.cpp_name}() ? {_member(item)}.view() : ::std::string_view{{}}",
-                f"has_{item.cpp_name}() ? {_member(item)}.view() : ::protocyte::Span<const char>{{}}",
+                f"has_{item.cpp_name}() ? {_member(item)}.view() : ::protocyte::StringView{{}}",
             )
         else:
             view_type = "::protocyte::Span<const ::protocyte::u8>"
@@ -1974,16 +1973,9 @@ def _runtime_scalar_type(cpp_type: str) -> str:
 def _emit_string_view_accessor(
     w: CppWriter,
     name: str,
-    string_view_expr: str,
-    span_expr: str | None = None,
+    expr: str,
 ) -> None:
-    if span_expr is None:
-        span_expr = string_view_expr
-    w.line("#if PROTOCYTE_ENABLE_STD_STRING_VIEW")
-    w.line(f"::std::string_view {name}() const noexcept {{ return {string_view_expr}; }}")
-    w.line("#else")
-    w.line(f"::protocyte::Span<const char> {name}() const noexcept {{ return {span_expr}; }}")
-    w.line("#endif")
+    w.line(f"::protocyte::StringView {name}() const noexcept {{ return {expr}; }}")
 
 
 def _file_uses_string_view(file_model: FileModel) -> bool:
diff --git a/src/protocyte/runtime/runtime.hpp b/src/protocyte/runtime/runtime.hpp
index d1ecf12..187b041 100644
--- a/src/protocyte/runtime/runtime.hpp
+++ b/src/protocyte/runtime/runtime.hpp
@@ -1316,6 +1316,12 @@ namespace protocyte {
         requires(!DataSizeSpanSource<Range &> && PointerSpanSource<Range &>)
     Span(Range &) -> Span<::std::remove_pointer_t<SpanBeginPointer<Range &>>>;
 
+#if PROTOCYTE_ENABLE_STD_STRING_VIEW
+    using StringView = ::std::string_view;
+#else
+    using StringView = Span<const char>;
+#endif
+
     template<class T>
     concept SpanSource = requires(T &value) { Span {value}; } || requires(const T &value) { Span {value}; };
 
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index 9413529..a55075b 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -211,6 +211,7 @@ def test_runtime_byte_containers_use_bulk_copy_helpers() -> None:
     assert "requires(::std::same_as<::std::remove_cv_t<T>, char>)" in span_body
     assert "return ::std::string_view {data_, size_};" in span_body
     assert "data_ == nullptr ? ::std::string_view {}" not in span_body
+    assert "#if PROTOCYTE_ENABLE_STD_STRING_VIEW\n    using StringView = ::std::string_view;\n#else\n    using StringView = Span<const char>;\n#endif" in runtime_header
     assert "using value_type = const char;" in string_body
     assert "Span<const char> view() const noexcept" in string_body
     assert "Span<const u8> byte_view() const noexcept" in string_body
@@ -690,13 +691,9 @@ def test_generated_header_contains_expected_field_api() -> None:
     assert "namespace demo {" in header
     assert "bool has_opt_name() const noexcept" in header
     assert "#include <string_view>" not in header
-    assert (
-        "  #if PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
-        "  ::std::string_view opt_name() const noexcept { return opt_name_.view(); }\n"
-        "  #else\n"
-        "  ::protocyte::Span<const char> opt_name() const noexcept { return opt_name_.view(); }\n"
-        "  #endif"
-    ) in header
+    assert "  ::protocyte::StringView opt_name() const noexcept { return opt_name_.view(); }" in header
+    assert "::std::string_view opt_name()" not in header
+    assert "::protocyte::Span<const char> opt_name()" not in header
     assert "struct Sample {" in header
     assert "typename Config::template Map<typename Config::String, ::protocyte::i32> items_;" in header
     assert "typename Config::template Box<::demo::Sample<Config>> self_;" in header
@@ -1447,12 +1444,11 @@ def test_generated_header_emits_tagged_union_oneofs() -> None:
     assert "destroy_at_(&choice.inner);" in header
     assert "#include <string_view>" not in header
     assert (
-        "  #if PROTOCYTE_ENABLE_STD_STRING_VIEW\n"
-        "  ::std::string_view text() const noexcept { return has_text() ? choice.text.view() : ::std::string_view{}; }\n"
-        "  #else\n"
-        "  ::protocyte::Span<const char> text() const noexcept { return has_text() ? choice.text.view() : ::protocyte::Span<const char>{}; }\n"
-        "  #endif"
+        "  ::protocyte::StringView text() const noexcept { "
+        "return has_text() ? choice.text.view() : ::protocyte::StringView{}; }"
     ) in header
+    assert "::std::string_view text()" not in header
+    assert "::protocyte::Span<const char> text()" not in header
     assert "union ChoiceStorage {" in header
     assert "ChoiceStorage() noexcept {}" in header
     assert "~ChoiceStorage() noexcept {}" in header