c++ - Illegal instruction (core dumped) upon compiling with SSE and -O3 options using latest g++ with a custom alignment allocator implementation -

when using g++ (gcc) 4.8.3 20140911 (red hat 4.8.3-7) compile following piece of code using compiling command "g++ -g -fno-omit-frame-pointer -msse2 -mssse3 -o3 memory.cpp", executable raises "illegal instruction (core dumped)" upon execution.

it compiles , runs without problems using same exact compiler flags using older g++ version. compiles , runs without problems when compiler flags "-mssse3 -o3" dropped or replaced lower optimization level such "-o2".

if usage both old , newer g++ compiler, having compiler flags "-msse2 -mssse3 -o3", , having portable aligned memory allocator requirement, options exist? there simple mistake in following piece of code fixed? finally, why did error exist?

when using gdb, line triggers error is: "memory[i] = (unsigned char)i;".

thanks in advance.

#include <iostream> using std::cerr; using std::cout; using std::endl; using std::flush; #include <stdlib.h>  void *aligned_alloc(int alignment, int size){   const int pointer_size = sizeof(unsigned char *);   const int requested_size = size + alignment - 1 + pointer_size;   unsigned char *base = (unsigned char *)malloc(requested_size);   if (base == null)  return null;   unsigned char *start = base + pointer_size;   const int trim_offset = (int)(((unsigned long long)(start+alignment-1)) & (alignment-1));   unsigned char *aligned = start + alignment - 1 - trim_offset;   *(unsigned char **)(aligned-pointer_size) = base;   return aligned; } void aligned_free(void **aligned){   if (*aligned == null)  return;   unsigned char *base = *(unsigned char **)((unsigned char *)(*aligned) - sizeof(unsigned char *));   free(base);   *aligned = null; }  int main(){   unsigned char *memory = (unsigned char *)aligned_alloc(16, 120);   if (memory == null){     cout<<"error: unable allocate memory."<<endl;     exit(1);   }    (int i=0; i<120; i++){     memory[i] = (unsigned char)i;   }    aligned_free((void **)&memory);    return 0; } 

this caused cpu didn't support ssse3 (supplemental streaming simd extensions 3) instruction subset (in particular, 3ghz p4 of flavor) trying run code compiled cpus support instruction subset; dropping -mssse3 flag gcc command line should enough cause offending instructions go away.