http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49653
Summary: Undefined reference to inlined function with -O0,-std=c99 Product: gcc Version: 4.5.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassig...@gcc.gnu.org ReportedBy: g...@intrepid.com Given, $ cat -n inline_trouble.c 1 inline long trouble(long a, long b) 2 { 3 return a + b; 4 } 5 6 long two = 2; 7 8 int main() 9 { 10 long result = trouble(two, two); 11 return (int)result; 12 } $ gcc --version gcc (GCC) 4.5.1 20100924 (Red Hat 4.5.1-4) This test compiles and links cleanly at -O2,-std=c99: $ gcc -std=c99 -O2 inline_trouble.c At -O0 -std=c99, it fails to link. $ gcc -std=c99 -O0 inline_trouble.c /tmp/ccXya7LE.o: In function `main': inline_trouble.c:(.text+0x1d): undefined reference to `trouble' collect2: ld returned 1 exit status Note that gnu90 doesn't have this issue. $ gcc -std=gnu90 -O0 inline_trouble.c (Although GCC 4.5.1 is used in the test above, it is likely that this problem can be reproduced with GCC built from the trunk.)