------- Comment #2 from tege-gcc at swox dot com 2008-02-21 13:49 ------- Created an attachment (id=15196) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15196&action=view) Alignment test
This is not a strictly correct test case, it may fail even if the compiler aligns the stack properly, and it may pass even if the compiler does not correctly align the stack. One needs to read the assembly output to verify that a failure is due to bad stack alignment. The idea is to check that two subsequent invocations of foo places a local variable at the same alignment mod 16. If the stack is aligned at 8 mod 16 as it should directly after the call instruction, any local variable should get the same mod 16 alignment every time. gcc 4.2.2 as well as gcc 4.2.3 fails this test on both Darwin and FreeBSD. The reason is that foo allocates 16 bytes on the stack, plus the 8 bytes implicitly allocated by call. This means the ABI required stack alignment of 16 is not maintained. $ gcc -O -m64 foo.c && ./a.out Abort trap: 6 (core dumped) -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35271
