Question

我正在尝试生成一个静态库并将其与执行二进制文件链接。

这是一个库函数：

#include <stdio.h>

int hello() {
    return 10;
}

使用这些命令，我可以得到一个静态库。

gcc -c io.c 
ar -crv libio.a io.o

使用lip -info，我检查它是x86_64架构。

ar> lipo -info libio.a 
input file libio.a is not a fat file
Non-fat file: libio.a is architecture: x86_64

这是使用该库的主要功能。

#include <stdio.h>
extern int hello();

int main(int argc, char *argv[]) {
    printf("%d", hello());
}

但是，当我将对象与静态库链接时，我有错误。

gcc main.c -lio -o main -L.

错误消息是：

ld: warning: ignoring file ./libio.a, file was built for archive which is not the architecture being linked (x86_64): ./libio.a
Undefined symbols for architecture x86_64:
  "_hello", referenced from:
      _main in main-2c41a0.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

我在ar中使用/bin/ar，使用clang-602.0.53时Mac OS X是10.10.2。

ar> clang -v
Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn)
Target: x86_64-apple-darwin14.3.0
Thread model: posix

可能有什么问题？

Answer 1

该库应该使用libtool -static生成。

gcc -c io.c 
libtool -static -o libio.a io.o
gcc main.c -lio -o main -L.
main

返回

10

ar> lipo -info libio.a 
input file libio.a is not a fat file
Non-fat file: libio.a is architecture: x86_64

ar> file libio.a 
libio.a: current ar archive

ar> nm libio.a 

io.o:
0000000000000000 T _hello

来自this page的提示。

Answer 2

从黑客攻击CMake生成make文件（CMakeFiles / test.dir / link.txt），默认情况下使用的/usr/local/ar中的ar似乎无法正常工作。

这是link.txt的内容。

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar qc libtest.a  CMakeFiles/test.dir/test.c.o   
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib libtest.a

从脚本中，/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar是我必须使用的那个。

smcho@macho ar> ls -alF /usr/bin/ar
-rwxr-xr-x  1 root  wheel  18160 Oct 17 18:49 /usr/bin/ar*
smcho@macho ar> ls -alF /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar 
-rwxr-xr-x  1 root  wheel  33472 Oct 29 16:36 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar*

同样，应该使用的ranlib是/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib而不是默认值。

smcho@macho ar> ls -alF `which ar`
-rwxr-xr-x  1 root  wheel  18160 Oct 17 18:49 /usr/bin/ar*
smcho@macho ar> ls -alF /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib
lrwxr-xr-x  1 root  wheel  7 Nov 10 21:10 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib@ -> libtool

除了需要使用-qc选项（来自cmake生成的脚本）

 -c      Whenever an archive is created, an informational message to that
         effect is written to standard error.  If the -c option is speci-
         fied, ar creates the archive silently. 
 -q      (Quickly) append the specified files to the archive.  If the ar-
         chive does not exist a new archive file is created.  Much faster
         than the -r option, when creating a large archive piece-by-piece,
         as no checking is done to see if the files already exist in the
         archive.

这些是获取正确库文件的命令：

clang -c hellolib.cpp -o hellolib.o
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar -qc libhello.a hellolib.o
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib libhello.a

用法是：

clang usehello.cpp -lhello -L.

nm和lipo显示正确的库文件信息：

smcho@macho ar> nm libhello.a 
libhello.a(hellolib.o):
0000000000000000 T __Z3addii
smcho@macho ar> lipo -info libhello.a 
input file libhello.a is not a fat file
Non-fat file: libhello.a is architecture: x86_64

Mac OS X的静态库链接问题：找不到架构x86_64的符号

2 个答案: