3 ms·

Its [errno's] value is significant only when the return value of the call indicated an error (i.e., -1 from most calls; -1 or NULL from most library fun

by avar 10y ago

Its [errno's] value is significant only when the return value of the call indicated an error (i.e., -1 from most calls; -1 or NULL from most library functions); a function that succeeds is allowed to change errno.

imron 10y ago
Note the difference between "is allowed" vs "must". If you write a program that relies on this behaviour you're going to have a hard to track down bug at some point.
- takeda 10y ago
  That's even stronger case for not relying on errno to catch errors. The code should be something like this: buf = calloc(huge, huge); if (!buf) perror("calloc failed"); printf("calloc(huge, huge) returned: %p\n", buf); free(buf);
  - deleted 10y ago
    [deleted]
  - imron 10y ago
    Yes, my post above was agreeing that you should check the error condition of the return value, rather than relying on errno to be cleared on success.
    - takeda 10y ago
      Ah, my bad.
ericfrederich 10y ago
Yeah... that caught my attention too and I looked up errno and found the same thing.