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Description of problem: Sorry if I'm doing this wrong but I've tried compiling the attached test program on a Ubuntu system and it works fine (using GCC 4.2.3). When attempting to use the Built-in functions for atomic memory access (http://gcc.gnu.org/onlinedocs/gcc-4.3.0/gcc/Atomic-Builtins.html#Atomic-Builtins), the built-in functions give an undefined reference error: [smc@localhost ~]$ gcc -Wall test.c /tmp/ccIRjIFU.o: In function `inc': test.c:(.text+0x15): undefined reference to `__sync_add_and_fetch_4' collect2: ld returned 1 exit status Version-Release number of selected component (if applicable): gcc-4.3.0-8 How reproducible: I've attached a simple program to demonstrate the problem. As best I can tell, this program should compile and link.
Created attachment 312027 [details] Test program source
That's user error. You can't use them on CPUs that don't support them. You likely don't have a plain i386 and i486 and higher already support them, so just compile with -march=i486, -march=i586, -march=i686 or higher.