5 ms·

buf = calloc(huge, huge); if (errno) perror("calloc failed"); printf("calloc(huge, huge) returned: %p\n", buf); free(buf); This has a flaw. errno d

by _RPM 10y ago

buf = calloc(huge, huge); if (errno) perror("calloc failed"); printf("calloc(huge, huge) returned: %p\n", buf); free(buf); This has a flaw. errno doesn't magically get reset to zero. You should check the return value of calloc, then use errno. Checking if(errno) is not the right way to determine if there was an error.

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.
int0x80 10y ago
wow, yeah, that's totally and obviously buggy ...