[Valgrind-users] Unhandled instruction bytes (C++, x86 on amd64)

[Lars C. <la...@be...>]

When I compile this simple C++ program as a 32-bit executable on a 64-bit
linux:

#include <iostream>
int main() {
        std::cout << "Hello, World!" << std::endl;
        return 0;
}

Using the -m32 option:

g++ -m32 out.cpp

Valgrind chokes on an supposedly illegal instruction:

vex x86->IR: unhandled instruction bytes: 0x67 0xE8 0x7D 0xFF
==18453== valgrind: Unrecognised instruction at address 0x48cc63d.
==18453==    at 0x48CC63D: std::locale::locale() (locale_init.cc:250)
==18453==    by 0x48C90DD: basic_streambuf (streambuf:466)
==18453==    by 0x48C90DD: stdio_sync_filebuf (stdio_sync_filebuf.h:80)
==18453==    by 0x48C90DD: std::ios_base::Init::Init() (ios_init.cc:85)
==18453==    by 0x108793: __static_initialization_and_destruction_0(int,
int) (in /home/lac/a.out)
==18453==    by 0x1087DB: _GLOBAL__sub_I_main (in /home/lac/a.out)
==18453==    by 0x10883A: __libc_csu_init (in /home/lac/a.out)
==18453==    by 0x4ABC724: (below main) (in /usr/lib32/libc-2.26.so)

The program works fine on its own though. Same program compiled for amd64
runs fine with valgrind.

An equivalent program written in C (using printf) works just fine with
valgrind, even when compiled for x86.

Bug or user error?

$ valgrind --version
valgrind-3.13.0

$ uname -a
Linux lnx 4.14.12-1-ARCH #1 SMP PREEMPT Fri Jan 5 18:19:34 UTC 2018 x86_64
GNU/Linux