构建ARM交叉工具链时libgcov.a缺失及功能异常的解决咨询

构建环境 #

• msys2-mingw64
• gcc版本：8.1.0 (x86_64-posix-seh-rev0, Built by MinGW-W64 project)
• 源码包：binutils-2.34、gcc-11.4.0、gmp-6.1.0、isl-0.18、mpc-1.0.3、mpfr-3.1.4、newlib-4.1.0
• 配置脚本：

#! /bin/bash

TOP_PATH="$(pwd)"
TARGET_GCC=arm-ACoreOS-eabi

INSTALL_PATH=${TOP_PATH}/install
BUILD_PATH=${TOP_PATH}/build

set -e
set -x

#Clean up the compilation process file
rm -rf ${INSTALL_PATH} ${BUILD_PATH}
mkdir ${INSTALL_PATH} ${BUILD_PATH}

#Libs
mkdir ${BUILD_PATH}/gmp
cd ${BUILD_PATH}/gmp
../../src/gmp-6.1.0/configure --build=x86-w64-mingw32 --prefix=${INSTALL_PATH} --enable-static --disable-shared
make all -j16
make install

mkdir ${BUILD_PATH}/isl
cd ${BUILD_PATH}/isl
../../src/isl-0.18/configure --build=x86-w64-mingw32 --prefix=${INSTALL_PATH} --enable-static --disable-shared  --with-gmp-prefix=${INSTALL_PATH}
make all -j16
make install

mkdir ${BUILD_PATH}/mpfr
cd ${BUILD_PATH}/mpfr
../../src/mpfr-3.1.4/configure --build=x86-w64-mingw32 --prefix=${INSTALL_PATH} --enable-static --disable-shared --with-gmp=${INSTALL_PATH}
make all -j16
make install

mkdir ${BUILD_PATH}/mpc
cd ${BUILD_PATH}/mpc
../../src/mpc-1.0.3/configure --build=x86-w64-mingw32 --prefix=${INSTALL_PATH} --enable-static --disable-shared  --with-gmp=${INSTALL_PATH} --with-mpfr=${INSTALL_PATH}
make all -j16
make install

#binutils
mkdir ${BUILD_PATH}/binutils
cd ${BUILD_PATH}/binutils
../../src/binutils-2.34/configure --build=x86-w64-mingw32 --target=${TARGET_GCC} --prefix=${INSTALL_PATH} --disable-multilib --disable-werror --enable-static --enable-shared
make all -j16
make install

#gcc all-gcc
mkdir ${BUILD_PATH}/gcc
cd ${BUILD_PATH}/gcc
../../src/gcc-11.4.0/configure --target=${TARGET_GCC} --prefix=${INSTALL_PATH} --enable-languages=c,c++ --enable-gcov --enable-plugin --enable-sanitizer --disable-shared --disable-nls --disable-libquadmath --disable-libssp --enable-version-specific-runtime-libs --with-gnu-as --with-gnu-ld --with-pkgversion='Anban ABFast GCC 2024-04-28' --disable-threads --disable-libstdcxx-pch --disable-bootstrap --disable-multilib --with-gmp=${INSTALL_PATH} --with-mpfr=${INSTALL_PATH} --with-mpc=${INSTALL_PATH} --with-isl=${INSTALL_PATH} --with-newlib --with-headers=/home/anban/src/newlib-4.1.0/newlib/libc/include --with-native-system-header=${INSTALL_PATH}/arm-ACoreOS-eabi/sys-include 'CFLAGS_FOR_TARGET=-O2 -g -fno-short-enums -mhard-float -mfpu=vfpv3 ' 'CXXFLAGS_FOR_TARGET=-O2 -g -fno-short-enums -mhard-float -mfpu=vfpv3' 'GOCFLAGS_FOR_TARGET=-O2 -g -fno-short-enums -mhard-float -mfpu=vfpv3' -v
make all-gcc -j16
make install all-gcc

#newlib
export PATH=$PATH:${INSTALL_PATH}/bin
mkdir ${BUILD_PATH}/newlib
cd ${BUILD_PATH}/newlib
../../src/newlib-4.1.0/configure --target=${TARGET_GCC} --prefix=${INSTALL_PATH} --disable-multilib --disable-werror --disable-threads 'CFLAGS_FOR_TARGET=-O2 -g -fno-short-enums -mhard-float -mfpu=vfpv3 ' 'CXXFLAGS_FOR_TARGET=-O2 -g -fno-short-enums -mhard-float -mfpu=vfpv3 ' 'GOCFLAGS_FOR_TARGET=-O2 -g -fno-short-enums -mhard-float -mfpu=vfpv3'
make all -j16
make install

#gcc all
cd ${BUILD_PATH}/gcc
make all -j16
make install all

echo ${TARGET_GCC} Compile complete!!!

问题现象 #

工具链构建成功，但产物中缺失libgcov.a。用该工具链编译后的目标代码反汇编显示__gcov_merge_add和__gcov_init都是空实现：

__gcov_merge_add:
0000000084016480:   bx lr
 33               void __gcov_init (struct gcov_info *p __attribute__ ((unused))) {}
                  __gcov_init:
0000000084016484:   bx lr

解决方案 #

1. 调整GCC配置参数 #

当前配置中的--disable-shared会影响libgcov的构建，需优化配置项：

• 保留依赖库的--enable-static --disable-shared，但GCC配置中需确保gcov相关组件能正常编译
• 添加--enable-gcov-support（GCC 11+专属的gcov完整支持开关）
• 在CFLAGS_FOR_TARGET和CXXFLAGS_FOR_TARGET中加入-fprofile-arcs -ftest-coverage，确保目标端编译时默认包含gcov所需的编译标记
• 确认--with-newlib配合配置：newlib需开启必要的IO支持，可在newlib配置时添加--enable-newlib-io-long-long

修改后的GCC配置命令片段：

../../src/gcc-11.4.0/configure --target=${TARGET_GCC} --prefix=${INSTALL_PATH} \
--enable-languages=c,c++ --enable-gcov --enable-gcov-support \
--enable-plugin --enable-sanitizer --enable-static --disable-shared \
--disable-nls --disable-libquadmath --disable-libssp \
--enable-version-specific-runtime-libs --with-gnu-as --with-gnu-ld \
--with-pkgversion='Anban ABFast GCC 2024-04-28' --disable-threads \
--disable-libstdcxx-pch --disable-bootstrap --disable-multilib \
--with-gmp=${INSTALL_PATH} --with-mpfr=${INSTALL_PATH} --with-mpc=${INSTALL_PATH} \
--with-isl=${INSTALL_PATH} --with-newlib \
--with-headers=/home/anban/src/newlib-4.1.0/newlib/libc/include \
--with-native-system-header=${INSTALL_PATH}/arm-ACoreOS-eabi/sys-include \
'CFLAGS_FOR_TARGET=-O2 -g -fno-short-enums -mhard-float -mfpu=vfpv3 -fprofile-arcs -ftest-coverage' \
'CXXFLAGS_FOR_TARGET=-O2 -g -fno-short-enums -mhard-float -mfpu=vfpv3 -fprofile-arcs -ftest-coverage' \
-v

2. 手动调整GCC源码宏定义 #

若配置参数调整后仍无效，需修改GCC源码中的宏：

• 在gcc/config/arm/t-arm文件中添加LIBGCOV = -lgcov，确保链接阶段自动关联libgcov
• 检查gcc/gcov-io.h，确保HAVE_GCOV_FLUSH宏已定义，若未定义则添加#define HAVE_GCOV_FLUSH 1
• 在gcc/config/newlib.h中添加#define TARGET_GCOV_SUPPORT 1，开启newlib环境下的gcov支持

3. 重新编译工具链 #

清理旧构建目录，执行修改后的编译脚本：

rm -rf ${INSTALL_PATH} ${BUILD_PATH}
mkdir ${INSTALL_PATH} ${BUILD_PATH}
# 执行完整编译流程

4. 验证功能 #

编译测试代码时添加-fprofile-arcs -ftest-coverage选项，调用__gcov_flush()后检查是否生成.gcda文件，确认libgcov功能正常。

内容的提问来源于stack exchange，提问作者Liu yishou