Problem with -fast build on sunstudio 8

Question

We migrated a large application from C 6.2 to sunstudio 8.
Our configuration is:
CC -V
CC: Sun C++ 5.5 2003/03/12
uname -a
SunOS soldev1 5.8 Generic_108528-21 sun4u sparc SUNW,Sun-Fire-480R
We have a test case which works on the debug build. But on a build with the -fast option, it fails on a function return value getting corrupted. The code looks like this:
File1.cpp
bool x = objA.func1(arg1,arg2,arg3);
if ( ! x ) {
cout << "objA.func1 returned false" << endl;
File2.cpp
bool A::func1(unsinged char*& arg1, const B& arg2, const c& arg3) {
if (someCondition) {
if (!func2(arg1,arg2,arg3)) {
return false;
cout << "returning true" << endl;
return true;
It prints:
returning true
objA.func1 returned false
We tried running memory access check, but did not help.
We tried to reduce the optimization level to -xO4 and it did not help either.
Any help on this would be greatly appreciated.

Answer 1

You might be running into a compiler bug, but the sample code you posted can't be compiled. If you provide a compilable example, I can tell you more.
But first, try compiling with no optimization options, and with +d (to disable function inlining). That will help narrow the range of possible causes.
Since we're on the topic of -fast, let me add a comment about that option. The User's Guide contains some warnings about this option, with pointers to other documentation about the related options.
The short answer is the -fast is not appropriate for programs that will run on machines other than the one that built the program. It is also not appropriate for programs that need accurate floating-point arithmetic. The exact effects of -fast differ among compiler releases, and sometimes from patch to patch.
Production programs should not use -fast, but should determine the optimization options that are appropriate for the range of systems to be supported, and use just those. You should also conduct performance testing to verify that the options you select produce good results for your particular program.