3 ms·

That reminds me of my favorite bug in a C program I ever delt with. We had a dorm floors' worth of "Intro to C" students pouring over our friend's buggy program

That reminds me of my favorite bug in a C program I ever delt with. We had a dorm floors' worth of "Intro to C" students pouring over our friend's buggy program. With a enough printfs() I was able to whittle the problem down to: A local variable "b" was changing after some function call that looked like: "call(&a)". Turns out because our program looked like "{ int a[3]; int b; ... call(&a); }" an off by one error accessing "a[4]" in the function was overwriting variables never passed to it! Felt like the champ figuring out. (This is a 15 year old story from freshman year, so I hope I got the details right.)

nindalf 5y ago
That’s horrifying.
cozzyd 5y ago
valgrind is your friend!
- benibela 5y ago
  That does not really work for stack variables
  - renox 5y ago
    There is ASAN https://github.com/google/sanitizers/wiki/AddressSanitizer https://github.com/google/sanitizers/wiki/AddressSanitizer which may work for stack variable though.
kjeetgill 5y ago
Update, since this got attention: I remembered slightly wrong: "b" would need to be declared before "a", not after and you'd access it with "a[3]" not "a[4]". So after this, "b" would be 7: "int b=5; int a[3]; a[3]=7;". Looks like I'm still making the same mistakes. But still: If you passed the array and referenced it wrong it would change local variables in some remote stack frame.