>>>>> "Peter" == Peter <pmc@xxxxxxxxxxxxxxxxxxxxxxx> writes: Peter> esp 0x7fbfc15c 0x7fbfc15c And there we go; the stack is misaligned. (only 4 byte alignment where 16 is expected). Peter> eip 0x838bdf2 0x838bdf2 Peter> 0x0838bdf2 <pg_checksum_page+866>: movaps 0x20(%esp),%xmm0 MOVAPS is an SSE (not SSE2) instruction; it's enabled by virtue of the fact that you used -march=pentium3 (the pentium3 supports SSE but not SSE2). The "A" stands for "aligned"; an unaligned source address causes an exception. %esp+0x20 is not correctly aligned for the instruction. GCC defaults to using a 16-byte stack alignment, but it relies on the caller to align the stack too, so if a GCC-compiled function is called from code that doesn't align the stack, then this kind of error can result. I do not know offhand (but I plan to find out) what clang's default stack alignment on i386 is. You can tell GCC to realign the stack itself using the -mstackrealign option. This problem shows up only with GCC and not with clang because clang does not attempt to use SSE to vectorize this particular piece of code. The non-vectorized implementation generated by clang has no special requirements for stack alignment. But at the end of the day this is not a problem with PostgreSQL - it would show up with any code compiled with GCC where the compiler had elected to use SSE instructions for optimization. -- Andrew (irc:RhodiumToad)
