Question

I have a code like this

char *verboseBuf = NULL;
if(somethin){
    for(a loop){
        for(another loop){
            if(somethin else){
                if(curl execution){
                    if(fail){
                        verboseBuf = (char *) malloc(sizeof(char) * (currSize +1));
                        fread(verboseBuf, 1, currSize, verboseFd);
                        verboseBuf[currSize + 1] = '\0';
                        string verbose = verboseBuf;
                        free(verboseBuf);
                    }   
                }   
            }   
        }   
    }   
}

The only place that i use the verboseBuf is inside the final if loop. but i get

*** glibc detected *** ./test: double free or corruption (!prev): 0x13c13290 ***

But how can be freeing it twice if i only use it in one place? and everytime i use it, i free it.
I tried using addr2line to find the place where it was freed previously but all got was a ??:0.

Answer 1

This line is writing one byte past the end of your buffer.

verboseBuf[currSize + 1] = '\0';