free memory not clears the memory block

Question

I am using DllImport to call method in c wrapper library from my own .net class. This method in c dll creates a string variable and returns the pointer of the string.

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Answer 1

Freeing memory doesn't clear it, it just frees it up so it can be re-used. Some debug builds will write over the memory for you to make it easier to find problems with values such as 0xBAADFOOD

Callers should allocate memory, never pass back allocated memory:

_declspec(dllexport) int ReturnString(char*buffer, int bufferSize)
{
    if (bufferSize < 125) {
        return 125;
    } else {
        strcat(buffer, "SOMETEXT");
        strcat(buffer, "SOMETEXT MORE");
        return 0;
    }
}