From 6b4cb0b42be465e4a662b1530546c5b249702879 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=9F=83=E5=8D=9A=E6=8B=89=E9=85=B1?= <vhtmfu@outlook.com>
Date: Sat, 4 Apr 2026 22:58:28 +0800
Subject: [PATCH] GNUmakefile: fix portability issues for out-of-tree and cross
 builds

- Use $(VPATH) instead of $(SRC) in define_from_arch.h: the comment on
  line 4 says "the VPATH variable must point to the actual makefile
  directory", making $(VPATH) the designated source-directory variable.
  $(SRC) happens to resolve to the same value in normal builds, but
  $(VPATH) is semantically correct and consistent with the rest of the
  file (CPPFLAGS already uses -I$(VPATH)).

- Use $< instead of $(SRC)$< in COMPILE macro: VPATH already resolves
  $< to the correct source path.  $(SRC)$< duplicates the directory
  prefix in out-of-tree builds (e.g. ../../src/../../src/cli/cli.c).

- Replace egrep with grep -E: egrep has been deprecated by POSIX
  (IEEE Std 1003.1-2024) and GNU grep now emits a warning.  On some
  systems (e.g. MSYS2), egrep is a wrapper script whose shebang path
  may contain spaces, breaking $(shell) invocations.

- Add READELF variable (?= $(CROSS_COMPILE)readelf) and use it in
  the loader-info.c rule instead of hardcoded readelf, matching the
  existing pattern for CC, STRIP, OBJCOPY, and OBJDUMP.

- Use $(VPATH) prefix for loader-info.awk in the loader-info.c rule
  so out-of-tree builds can find the awk script.
---
 src/GNUmakefile | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/GNUmakefile b/src/GNUmakefile
index 96035576..785efab0 100644
--- a/src/GNUmakefile
+++ b/src/GNUmakefile
@@ -11,6 +11,7 @@ INSTALL  = install
 CC       ?= $(CROSS_COMPILE)gcc
 LD       = $(CC)
 STRIP    ?= $(CROSS_COMPILE)strip
+READELF  ?= $(CROSS_COMPILE)readelf
 OBJCOPY  ?= $(CROSS_COMPILE)objcopy
 OBJDUMP  ?= $(CROSS_COMPILE)objdump
 
@@ -86,7 +87,7 @@ OBJECTS += \
 	extension/fix_symlink_size/fix_symlink_size.o
 
 define define_from_arch.h
-$2$1 := $(shell $(CC) $1 -E -dM -DNO_LIBC_HEADER $(SRC)/arch.h | grep -w $2 | cut -f 3 -d ' ')
+$2$1 := $(shell $(CC) $1 -E -dM -DNO_LIBC_HEADER $(VPATH)/arch.h | grep -w $2 | cut -f 3 -d ' ')
 endef
 
 $(eval $(call define_from_arch.h,,HAS_LOADER_32BIT))
@@ -169,7 +170,9 @@ BUILD_ID_NONE := $(shell if ld --build-id=none --version >/dev/null 2>&1; then e
 ######################################################################
 # Build rules
 
-COMPILE = $($(quiet)CC) $(CPPFLAGS) $(CFLAGS) -MD -c $(SRC)$< -o $@
+# Use $< instead of $(SRC)$< because VPATH already resolves source paths.
+# $(SRC)$< duplicates the prefix in out-of-tree builds.
+COMPILE = $($(quiet)CC) $(CPPFLAGS) $(CFLAGS) -MD -c $< -o $@
 LINK    = $($(quiet)LD) -o $@ $^ $(LDFLAGS)
 
 OBJIFY = $($(quiet)GEN)									\
@@ -186,7 +189,7 @@ proot: $(OBJECTS)
 
 # Special case to compute which files depend on the auto-generated
 # file "build.h".
-USE_BUILD_H := $(patsubst $(SRC)%.c,%.o,$(shell egrep -sl 'include[[:space:]]+"build.h"' $(patsubst %.o,$(SRC)%.c,$(OBJECTS))))
+USE_BUILD_H := $(patsubst $(SRC)%.c,%.o,$(shell grep -E -sl 'include[[:space:]]+"build.h"' $(patsubst %.o,$(SRC)%.c,$(OBJECTS))))
 $(USE_BUILD_H): build.h
 
 %.o: %.c
@@ -235,7 +238,7 @@ $(eval $(call build_loader,-m32))
 endif
 
 loader/loader-info.c: loader/loader
-	readelf -s $< | awk -f loader/loader-info.awk > $@
+	$(READELF) -s $< | awk -f $(VPATH)/loader/loader-info.awk > $@
 
 ######################################################################
 # Dependencies