c - 构建 OpenWrt 包的链接器错误

Question

我正在构建一个小的 OpenWRT 应用程序，我想将一个库静态链接到它。

编辑:其他库也会发生这种情况，而不仅仅是 libcurl。

我在构建它时遇到这个错误:

make[3]: Entering directory `/home/md/work/openwrt/build_dir/target-mips_r2_uClibc-0.9.33.2/app'
mips-openwrt-linux-uclibc-gcc -c -Os -pipe -mips32r2 -mtune=34kc -mno-branch-likely -fno-caller-saves -fhonour-copts -Wno-error=unused-but-set-variable -msoft-float -Wall -Werror main.c -o main.o
mips-openwrt-linux-uclibc-gcc -Os -pipe -mips32r2 -mtune=34kc -mno-branch-likely -fno-caller-saves -fhonour-copts -Wno-error=unused-but-set-variable -msoft-float -Wall -Werror -L/home/md/work/openwrt/staging_dir/target-mips_r2_uClibc-0.9.33.2/usr/lib -L/home/md/work/openwrt/staging_dir/target-mips_r2_uClibc-0.9.33.2/lib -L/home/md/work/openwrt/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/usr/lib -L/home/md/work/openwrt/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/lib -Wl,-Bstatic -lcurl main.o -o app
/home/md/work/openwrt/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/lib/gcc/mips-openwrt-linux-uclibc/4.6.4/../../../../mips-openwrt-linux-uclibc/bin/ld: cannot find -lgcc_s
/home/md/work/openwrt/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/lib/gcc/mips-openwrt-linux-uclibc/4.6.4/../../../../mips-openwrt-linux-uclibc/bin/ld: cannot find -lgcc_s
collect2: ld returned 1 exit status
make[3]: *** [app] Error 1

这很奇怪，因为我在搜索路径上有 libgcc_s.so:

stormbreaker:openwrt> find . -name libgcc_s.*
./build_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/uClibc-0.9.33.2/libc/sysdeps/linux/common/libgcc_s.h
./build_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/gcc-linaro-4.6-2012.12-final/gcc/libgcc_s.so
./build_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/gcc-linaro-4.6-2012.12-final/gcc/libgcc_s.so.1
./build_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/gcc-linaro-4.6-2012.12-final/mips-openwrt-linux-uclibc/libgcc/libgcc_s.so
./build_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/gcc-linaro-4.6-2012.12-final/mips-openwrt-linux-uclibc/libgcc/libgcc_s.so.1
./build_dir/target-mips_r2_uClibc-0.9.33.2/toolchain/ipkg-ar71xx/libgcc/lib/libgcc_s.so.1
./build_dir/target-mips_r2_uClibc-0.9.33.2/toolchain/libgcc_s.so.1
./staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/lib/libgcc_s.so
./staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/lib/libgcc_s.so.1
./staging_dir/target-mips_r2_uClibc-0.9.33.2/root-ar71xx/lib/libgcc_s.so
./staging_dir/target-mips_r2_uClibc-0.9.33.2/root-ar71xx/lib/libgcc_s.so.1

我用 -rpath 和 -rpath-link 尝试了一些 hack，但得到了相同的结果。据我所知，libcurl 不需要 libgcc_s。

我创建了一个简单的案例来重现这一点:

openwrt/package/app/Makefile相关部分:

TARGET_CFLAGS += -Wall -Werror
TARGET_LIBS = -Wl,-Bstatic -lcurl

define Build/Compile
    CC="$(TARGET_CC)" \
    CFLAGS="$(TARGET_CFLAGS)" \
    LDFLAGS="$(TARGET_LDFLAGS)" \
    LIBS="$(TARGET_LIBS)" \
    $(MAKE) -C $(PKG_BUILD_DIR)
endef

openwrt/package/app/src/Makefile:

APP = app
SOURCES = $(wildcard *.c)
OBJECTS = $(SOURCES:.c=.o)

$(APP): $(OBJECTS)
    $(CC) $(CFLAGS) $(LDFLAGS) $(LIBS) $(OBJECTS) -o $(APP)

# Objects
%.o: %.c
    $(CC) -c $(CFLAGS) $< -o $@

应用程序本身是一个文件:

#include <stdio.h>
#include <curl/curl.h>

int main (void)
{
    curl_global_init(CURL_GLOBAL_ALL);
    printf("Ok!\n");
    return 0;
}

Answer 1

增加链接器的详细程度(使用 -Wl,--verbose=99)给了我这些线索:

...
attempt to open /home/md/work/openwrt/staging_dir/target-mips_r2_uClibc-0.9.33/usr/lib/libgcc_s.a failed
attempt to open /home/md/work/openwrt/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33/lib/gcc/mips-openwrt-linux-uclibc/4.6.3/libgcc_s.a failed
attempt to open /home/md/work/openwrt/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33/lib/gcc/mips-openwrt-linux-uclibc/4.6.3/../../../../mips-openwrt-linux-uclibc/lib/libgcc_s.a failed
attempt to open /home/md/work/openwrt/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33/mips-openwrt-linux-uclibc/bin/../../../toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33/usr/local/lib/libgcc_s.a failed
attempt to open /home/md/work/openwrt/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33/mips-openwrt-linux-uclibc/bin/../../../toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33/lib/libgcc_s.a failed
attempt to open /home/md/work/openwrt/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33/mips-openwrt-linux-uclibc/bin/../../../toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33/usr/lib/libgcc_s.a failed
etc.

看起来 libgcc_s 的静态版本丢失了。

无论如何，我将我的包 Makefile 更改为:

TARGET_LIBS = -Wl,-Bdynamic -lgcc_s \
              -Wl,-Bstatic -lcurl

define Build/Compile
    $(TARGET_CONFIGURE_OPTS) \
    CFLAGS="$(TARGET_CFLAGS)" \
    LDFLAGS="$(TARGET_LDFLAGS)" \
    LIBS="$(TARGET_LIBS)" \
    $(MAKE) -C $(PKG_BUILD_DIR)
endef

对我有用 =)

我理解为什么与静态库链接需要其依赖项的静态版本，但我没想到链接器会在我背后做这件事，而不是先回退到动态版本。