在 MacOSX 上静态链接时找不到符号

Question

我正在尝试创建一个静态库并在 MacOS X（多个版本）上 link 它：文件 foo.c:

char foo[111];

文件bar.c:

#include <string.h>

extern char foo[];

int bar(char *src) {
  strcpy(foo, src);
  return strlen(foo);
}

创建库：

$ cc -c foo.c bar.c
$ ar r libfoobar.a foo.o bar.o
ar: creating archive libfoobar.a
$ ranlib libfoobar.a 
$ nm libfoobar.a 

libfoobar.a(foo.o):
000000000000006f C _foo

libfoobar.a(bar.o):
                 U ___strcpy_chk
0000000000000000 T _bar
                 U _foo
                 U _strlen

创建一个小测试程序：

文件main.c:

#include <stdio.h>

int bar(char *);

int main(void) {
  printf("foobarbar = %i\n", bar("123"));
  return 0;
}

编译并link:

$ cc -c main.c
$ cc -o m main.o -L. -lfoobar
Undefined symbols for architecture x86_64:
  "_foo", referenced from:
      _bar in libfoobar.a(bar.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

为什么找不到符号？定义在foo.c?至少 ranlib 不应该在库中创建一个索引，允许那里的文件随机排序吗？

相同的代码在 Linux (gcc) 下运行良好，并且当 foo.c 中的符号不是 char 数组，而是 int 时也是如此。

Answer 1

有个类似的问题： which has :

Option 1:

ar -rs my_archive.a foo.o bar.o other_object_files.o
ranlib -c my_archive.a

Option 2:

libtool -c -static -o my_archive.a foo.o bar.o other_object_files.o

-c 标志分别对 ranlib 和 libtool 上的两个选项产生影响：

-c

Include common symbols as definitions with respect to the table of contents. This is seldom the intended behavior for linking from a library, as it forces the linking of a library member just because it uses an uninitialized global that is undefined at that point in the linking. This option is included only because this was the original behavior of ranlib. This option is not the default.

在 MacOSX 上静态链接时找不到符号

Symbol not found when static linking on MacOSX

linker

clang

static-libraries