Program crashing in optimized or default mode

[lace28]

Hi,

My program is crashing only when it's compiled in optimized or default mode. It does not crash in debug mode. The cpu goes up to 100%, the memory increases real fast and the program crashes shortly after.

Here's what I'm developping on:
CentOS 5.3
Kernel 2.6.18-218.1.16.el5
KDevelop 3.3.4
GCC 4.1.2

I think I have narrowed down the problem to a specific function in the program. It's fairly simple here's the code:

bool MyClass::ReadData()
{
    unsigned char* buffer;
    stringstream bufferStream;
    int bytes_read;

    try
    {
        // fileID is declared in a parent class and is assigned a value in a
        // previous function
        ioctl(fileID, FIONREAD, &bytes_read);
        
        if (bytes_read > 0)
        {            
            buffer = (unsigned char*) malloc(bytes_read);
            
            read(fileID, buffer, bytes_read);

            // Get the numeric value of each byte in the buffer
            for (int bufferIndex = 0; bufferIndex < bytes_read; bufferIndex++)
                bufferStream << (int)buffer[bufferIndex] << ',';

            // Convert bufferStream to a string;
            // rawData is declared in a parent class;
            rawData = bufferStream.str(); 

            // Free the memory
            free(buffer);
            
            return true;
        }
    }
    catch (exception& e)
    {
        ErrorHelper::LogError(e.what());
    }
    catch (...)
    {      
        ErrorHelper::LogError("Unknown error");
    }

    return false;
};

Here are some facts:
If I comment the rawData line it does not crash.
If I add a line ErrorHelper::LogError("anything") at the beginning of the function or right after the rawdata line it does not crash... what the hell?!?

Any clue because I'm clueless at this point.

Thanks.

Olivier

[Bazzy]

How was rawData declared?

[lace28]

string rawData;

[lace28]

New facts:

Changing the CXXFLAGS -O2 option in the makefile to -O1 made the problem dissapear, but I don't know why. I know that -O2 means several more optimization flags are used by the compiler.

Leaving the makefile intact (with the -O2) and adding the following line of code at the end of my function(after free(buffer)) also made the problem dissapear:

bufferStream.str(""); // Clear buffer stream 

Again I'm not sure if this is just a coincidence or not but it was recommended to me so it's probably not a bad thing to do.

I'd sure like to understand all of this so any help is welcome.