Created attachment 68202 [details]
Calls atof

I'm running Gentoo on a Core i5 and I've built glibc with "-O2 --march=native".  It seems that some optimization generates an instruction that valgrind doesn't understand.

I've attached a fairly simple test program (test.c) that can be built with "gcc test.c -o test".  The test just consists of running atof on a constant string.

I'm running glibc 2.13, valgrind 3.7.0 and GCC 4.5.3.  My CPU is reported as a "Intel(R) Core(TM) i5-2500K CPU" by /proc/cpuinfo.

Here is the output I get from valgrind running on my optimized glibc (built with "-O2 --march=native"):
$ valgrind ./test
==29368== Memcheck, a memory error detector
==29368== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==29368== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==29368== Command: ./test
==29368== 
vex amd64->IR: unhandled instruction bytes: 0xC5 0xFB 0x10 0x44 0x24 0xF8 0xC3 0x90
==29368== valgrind: Unrecognised instruction at address 0x4e74f13.
==29368==    at 0x4E74F13: __mpn_construct_double (in /lib64/libc-2.13.so)
==29368==    by 0x4E6D6B3: ____strtod_l_internal (in /lib64/libc-2.13.so)
==29368==    by 0x40059C: main (in /home/palmer/.local/src/valgrind/test)
==29368== Your program just tried to execute an instruction that Valgrind
==29368== did not recognise.  There are two possible reasons for this.
==29368== 1. Your program has a bug and erroneously jumped to a non-code
==29368==    location.  If you are running Memcheck and you just saw a
==29368==    warning about a bad jump, it's probably your program's fault.
==29368== 2. The instruction is legitimate but Valgrind doesn't handle it,
==29368==    i.e. it's Valgrind's fault.  If you think this is the case or
==29368==    you are not sure, please let us know and we'll try to fix it.
==29368== Either way, Valgrind will now raise a SIGILL signal which will
==29368== probably kill your program.
==29368== 
==29368== Process terminating with default action of signal 4 (SIGILL)
==29368==  Illegal opcode at address 0x4E74F13
==29368==    at 0x4E74F13: __mpn_construct_double (in /lib64/libc-2.13.so)
==29368==    by 0x4E6D6B3: ____strtod_l_internal (in /lib64/libc-2.13.so)
==29368==    by 0x40059C: main (in /home/palmer/.local/src/valgrind/test)
==29368== 
==29368== HEAP SUMMARY:
==29368==     in use at exit: 0 bytes in 0 blocks
==29368==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==29368== 
==29368== All heap blocks were freed -- no leaks are possible
==29368== 
==29368== For counts of detected and suppressed errors, rerun with: -v
==29368== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from 6)
Illegal instruction

And here is the output on a less-optimized glibc (just built with "-O2"):
$ valgrind ./test
==3851== Memcheck, a memory error detector
==3851== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==3851== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==3851== Command: ./test
==3851== 
d: -2.000000
==3851== 
==3851== HEAP SUMMARY:
==3851==     in use at exit: 0 bytes in 0 blocks
==3851==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==3851== 
==3851== All heap blocks were freed -- no leaks are possible
==3851== 
==3851== For counts of detected and suppressed errors, rerun with: -v
==3851== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from 6)