c-使用-mpopcnt编译会导致非法指令错误

我编译以下C代码

// main.cpp
#include <cstdio>

int main() {
  unsigned char tab[4] = {0};
  printf("%d\n", __builtin_popcount(*((int *)tab)));
}

使用命令行：

g++ -o prog main.cpp -mpopcnt

运行程序时出现错误：

Illegal instruction

不使用-mpopcnt进行编译不会产生错误(仅显示0).

问题：是什么原因导致此错误？

我正在同一台计算机上编译并运行该程序.
Valgrind没有发现任何问题.跑步

valgrind --leak-check=full ./prog

给

==12917== Memcheck, a memory error detector
==12917== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==12917== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==12917== Command: ./prog
==12917== 
0
==12917== 
==12917== HEAP SUMMARY:
==12917==     in use at exit: 0 bytes in 0 blocks
==12917==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==12917== 
==12917== All heap blocks were freed -- no leaks are possible
==12917== 
==12917== For counts of detected and suppressed errors, rerun with: -v
==12917== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2)

下面,我给出一些系统规格.

我正在使用Ubuntu 12.04.跑步

uname -a

给我

Linux wtu-82 3.2.0-65-generic #99-Ubuntu SMP Fri Jul 4 21:03:29 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

跑步

g++ -v

给

Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.6.4-1ubuntu1~12.04' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.6.4 (Ubuntu/Linaro 4.6.4-1ubuntu1~12.04)

输出

cat /proc/cpuinfo

是

processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 23
model name  : Intel(R) Core(TM)2 Duo CPU     E8500  @ 3.16GHz
stepping    : 10
microcode   : 0xa0c
cpu MHz     : 2000.000
cache size  : 6144 KB
physical id : 0
siblings    : 2
core id     : 0
cpu cores   : 2
apicid      : 0
initial apicid  : 0
fpu     : yes
fpu_exception   : yes
cpuid level : 13
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm dtherm tpr_shadow vnmi flexpriority
bogomips    : 6317.48
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

processor   : 1
vendor_id   : GenuineIntel
cpu family  : 6
model       : 23
model name  : Intel(R) Core(TM)2 Duo CPU     E8500  @ 3.16GHz
stepping    : 10
microcode   : 0xa0c
cpu MHz     : 2000.000
cache size  : 6144 KB
physical id : 0
siblings    : 2
core id     : 1
cpu cores   : 2
apicid      : 1
initial apicid  : 1
fpu     : yes
fpu_exception   : yes
cpuid level : 13
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm dtherm tpr_shadow vnmi flexpriority
bogomips    : 6317.38
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

解决方法:

POPCNT在SSE 4.2中引入.您的处理器是SSE 4.1.因此,该指令完全丢失了.当使用-mpopcnt强制编译器使用处理器不知道的指令生成代码时,会出现非法指令错误.

标签：g,linux,c-4
来源： https://codeday.me/bug/20191120/2045661.html