I have the following program:

~/test> cat test.cc
int main()
{
  int i = 3;
  int j = __sync_add_and_fetch(&i, 1);
  return 0;
}

I'm compiling this program using GCC 4.2.2 on Linux running on a multi-cpu 64-bit Intel machine:

~/test> uname --all
Linux doom 2.6.9-67.ELsmp #1 SMP Wed Nov 7 13:56:44 EST 2007 x86_64 x86_64 x86_64 GNU/Linux

When I compile the program in 64-bit mode, it compiles and links fine:

~/test> /share/tools/gcc-4.2.2/bin/g++ test.cc
~/test>

When I compile it in 32-bit mode, I get the following error:

~/test> /share/tools/gcc-4.2.2/bin/g++ -m32 test.cc
/tmp/ccEVHGkB.o(.text+0x27): In function `main':
: undefined reference to `__sync_add_and_fetch_4'
collect2: ld returned 1 exit status
~/test>

Although I will never actually run on a 32-bit processor, I do need a 32-bit executable so I can link with some 32-bit libraries.

My 2 questions are:

  1. Why do I get a link error when I compile in 32-bit mode?

  2. Is there some way to get the program to compile and link, while still being able to link with a 32-bit library?

gcc linker atomic
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