Performance degradation with -g compiler option

Question

Hello
Our mearurement of simple program compiled with and without -g option shows big performance difference.
Machine:
SunOS xxxxx 5.10 Generic_137137-09 sun4u sparc SUNW,Sun-Fire-V250
Compiler:
CC: Sun C++ 5.9 SunOS_sparc Patch 124863-08 2008/10/16
#include "time.h"
#include <iostream>
int main(int  argc, char ** argv)
   for (int i = 0 ; i < 60000; i++)
       int *mass = new int[60000];
       for (int j=0; j < 10000; j++) {
           mass[j] = j;
       delete []mass;
   return 0;
}Compilation and execution with -g:
CC -g -o test_malloc_deb.x test_malloc.c
ptime test_malloc_deb.xreal 10.682
user 10.388
sys 0.023
Without -g:
CC -o test_malloc.x test_malloc.c
ptime test_malloc.xreal 2.446
user 2.378
sys 0.018
As you can see performance degradation of "-g" is about 4 times.
Our product is compiled with -g option and before shipment it is stripped using 'strip' utility.
This will give us possibility to open customer core files using non-stripped exe.
But our tests shows that stripping does not give performance of executable compiled without '-g'.
So we are losing performance by using this compilation method.
Is it expected behavior of compiler?
Is there any way to have -g option "on" and not lose performance?

Answer 1

In your original compile you don't use any optimisation flags, which tells the compiler to do minimal optimisation - you're basically telling the compiler that you are not interested in performance. Adding -g to this requests that you want maximal debug. So the compiler does even less optimisation, in order that the generated code more closely resembles the original source.
If you are interested in debug, then -g with no optimisation flags gives you the most debuggable code.
If you are interested in optimised code with debug, then try -O -g (or some other level of optimisation). The code will still be debuggable - you'll be able to map disassembly to lines of source, but some things may not be accessible.
If you are using C++, then -g will in SS12 switch off front-end inlining, so again you'll get some performance hit. So use -g0 to get inlining and debug.
HTH,
Darryl.