fix(merge): pin classic locale on CSV streams so integers can't get grouped#17
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Floats are written via fmt (locale-independent), but the integer columns
(qpc_freq header, display_time, thread_id, qpc/gpu values) go through
std::ostream operator<<, which uses the stream's locale. No CSV stream was
ever imbued, so a host that installed a thousands-grouping global locale --
some middleware / Qt launchers do, via std::locale::global(std::locale("")) --
would emit "1,234,567", injecting spurious fields and corrupting both the
per-side and merged CSVs (and the byte-equivalence with analyze.py, whose
Python side is always locale-independent).
Imbue std::locale::classic() on every CSV read/write stream: the FrameCsvSink
/ GpuCsvSink writer, WriteMergedCsv's output, and the two per-row parse
stringstreams in ReadFrameCsv / ReadGpuCsv. analyze.py needs no change
(Python int()/str()/csv don't honor the C locale), so the two paths stay
byte-equivalent.
Adds a test that installs a grouping global locale (portable custom
std::numpunct, RAII-restored so it can't leak into other cases) and asserts
WriteMergedCsv still emits raw integers; it runs in the CI test binary.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Finding #6 (code review): CSV corruption under a non-"C" global locale
Floats are written via
fmt(locale-independent), but the integer columns — the# qpc_freq=header,display_time,thread_id, and the qpc/gpu values — go throughstd::ostream operator<<, which honors the stream's locale. No CSV stream was ever imbued. A host that installs a thousands-grouping global locale (some middleware / Qt launchers do, viastd::locale::global(std::locale(""))) would make us emit1,234,567, injecting spurious fields and corrupting both the per-side and merged CSVs — and breaking byte-equivalence withanalyze.py.Fix
imbue(std::locale::classic())on every CSV read/write stream:FrameCsvSink/GpuCsvSink)layer.cppensureOpenmerge.cppWriteMergedCsvmerge.cppReadFrameCsv/ReadGpuCsvstringstreamsanalyze.pyneeds no change — Python'sint()/str()/csvdon't honor the C locale — so the two paths stay byte-equivalent. (<locale>added topch.h+merge.cpp.)Test
New
test_merge.cppcase installs a grouping global locale (portable customstd::numpunct, RAII-restored so it can't leak into other cases), confirms the locale is active, then assertsWriteMergedCsvstill emits raw integers (1234567,89012,present;1,234,567/89,012absent). It runs in the CI test binary (which CI executes and fails on non-zero exit).Pure additions (+68, no deletions); no lines >120 cols.
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