Package: clang
Version: 3.0-6
Severity: minor
Hi,
when compiling C code using memset in a bad way with clang, enabling
optimizations (-O1 / -O2 / -Os) creates binaries with an illegal instruction on
x86 and x86_64 systems:
zsh: illegal hardware instruction ./ill
valgrind: vex x86->IR: unhandled instruction bytes: 0xF 0xB 0x90 0x90
When using gcc (or clang without optimizations), the code terminates with a
segmentation fault, I believe this should happen for clang -O1 / -O2 as well.
This only happens when compiling _wrong_ code, so I'm not sure how much of a
bug this actually is.
A file to reproduce this (ill.c) is attached.
If I can provide any additional information, please let me know.
-- System Information:
Debian Release: wheezy/sid
APT prefers unstable
APT policy: (500, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 3.2.0-2-686-pae (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages clang depends on:
ii libc6 2.13-27
ii libclang-common-dev 3.0-6
ii libffi5 3.0.10-3
ii libgcc1 1:4.7.0-1
ii libllvm3.0 3.0-9
ii libstdc++6 4.7.0-1
ii libstdc++6-4.6-dev 4.6.3-1
Versions of packages clang recommends:
ii llvm-3.0-dev <none>
ii python 2.7.2-10
clang suggests no packages.
-- no debconf information
/*
* compiled with: clang -O2 -Wall -Wextra -o ill ill.c
*
* expected: segmentation fault
* actual result: illegal instruction (tested on x86 and x86_64)
* happens with -O1, -O2 and -Os, it's fine without optimization
*/
#include <stdlib.h>
#include <string.h>
struct __somestruct {
int a;
int b;
int c;
int d;
int e;
int f;
};
typedef struct __somestruct _somestruct;
typedef _somestruct *somestruct;
int main (void)
{
somestruct foo = NULL;
foo = malloc(sizeof(_somestruct));
memset(&foo, 0, sizeof(foo));
/* correct usage: */
/* memset(foo, 0, sizeof(_somestruct)); */
/* note: gcc -O2 optimizes this all away, so to compare it to gcc, the
* code may need to be more complex
*/
foo->a = 25;
return 0;
}
