Comment by jovial_cavalier

Comment by jovial_cavalier 2 months ago

So if a function dereferences a pointer, it doesn't make sense to check that it's not null inside the function?

Unless there's an actual performance implication, this is all purely a matter of taste. This is the kind of broadly true, narrowly false stuff that causes people to destroy codebases. "I can't write it this way, because I have to push ifs up and fors down!!!" It's a totally fake requirement, and it imposes a fake constraint on the design.

kazinator 2 months ago

If there is a performance implication of moving the if into the callers or not, you can do it with an inline function.

  static inline int function(blob *ptr, int arg)
  {
     if (ptr == NULL)
       return ERR_NULL;
     return real_function(ptr, arg);
  }

Just like that, we effectively moved the if statement into 37 callers, where the compiler may be smart enough to hoist it out of a for loop when it sees that the pointer is never changed in the loop body, or to eliminate it entirely when it sees that the pointer cannot be null.

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cakealert 2 months ago

IMO you should assert it's not null. There should never be a circumstance where you pass a null pointer to a function.

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kazinator 2 months ago
ISO C allows:
free(NULL); // convenient no-op, does nothing fflush(NULL); // flush all streams; done implicitly on normal exit time(NULL); // don't store time_t into a location, just return it strtol(text, NULL, 10); // not interested in pointer to first garbage char setbuf(stream, NULL); // allocate a buffer for stream realloc(NULL, size); // behave like malloc(size)
and others. More examples in POSIX and other APIs:
sigprocmask(SIG_UNBLOCK, these_sigs, NULL); // not interested in previous signal mask CreateEventA(NULL, FALSE, FALSE, NULL); // no security attributes, no name
Reality just ran over your opinion, oops!
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- cakealert 2 months ago
  
  I'm sorry. Are you claiming the people who designed those functions made good choices? They altered the behavior of the function considerably for a single input value that is more likely to be a bug than not.
  
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  kazinator 2 months ago
  
  Yes. I will probably continue to make similar choices of the future.
  
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