Today i was writing a benchmarking application in C to test the speed of the POSIX regular expression library implementation. I was writing the following while loop ...

while(fgets(line,BUF_SIZE,data) != NULL) {
    // split the line
    int index = indexOf(line,'\t');
    int len = strlen(line);
    int i = 0;

    line_r = substring(line,0,index);
    line_s = substring(line,index + 1,len - 1);

    if(regcomp(regex,line_r,REG_EXTENDED) != 0) {
        printf("Compile Failed for %s\n",line_r);
        free(line_r);
        free(line_s);
        continue;
    }
	
    [... other code here ...]
	
    free(line_r);
    free(line_s);
}

... and thinking what is more appropriate to do ... leave the code like that, duplicating the free functions of line_r and line_s, or using a label with a goto statement to the end of the loop ... ending with something like:

while(fgets(line,BUF_SIZE,data) != NULL) {
    // split the line
    int index = indexOf(line,'\t');
    int len = strlen(line);
    int i = 0;

    line_r = substring(line,0,index);
    line_s = substring(line,index + 1,len - 1);

    if(regcomp(regex,line_r,REG_EXTENDED) != 0) {
        printf("Compile Failed for %s\n",line_r);
        goto free;
    }
	
    [... other code here ...]
    
free:
    free(line_r);
    free(line_s);

}

Note: The substring allocates the buffer (i know that actually is bad policy) and i could do it avoiding the allocation for each line by using two big buffers (i have constant BUF_SIZE). Imagine that buf_size was variable and all buffers have to be allocated each time.

You might be interested to take a look at Go To Statement Considered Harmful by Edsger W. Dijkstra and this artcile from my supervisor Diomidis Spinellis in Dr. Dobbs journal.