Question

As a newb, like myself, to have great difficulty with searching the header files such as stdio.h for a function like getchar(). Somehow I picked up some information somewhere that I should not be afraid when looking in header files to “see how things work.” (C++ Primer Plus, Stephen Prata)

I am very inexperienced with header files to say the least, and programmig in general.

In my attempt to find getchar() I found that stdio.h simply branches to more and more headers, and locating getchar() became increasinly complicated and time consuming, and I never found it. Clearly I am going about this all wrong, my intention was merely to find some source code for functions I am using.

My question therefore is: Where can I find source code to truly ‘understand’ what the standard functions are ‘really’ doing?

Answer 1

If you’re looking for the declarations for variable order or other usage notes, just use an online reference or man.

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If you’re looking for the actual code, look into an implementation of the C standard library, like GNU’s libc.

It’s worth noting though, that implementations are not simple, and their graph of dependencies goes far and wide. They also tend to interact with the machine on a lower level than most of us are used to.

Consider libc’s implementation of getchar:

int
getchar ()
{
  int result;
  _IO_acquire_lock (_IO_stdin);
  result = _IO_getc_unlocked (_IO_stdin);
  _IO_release_lock (_IO_stdin);
  return result;
} 

Probably not what you were expecting :).

(Note: No idea how good of reference that is for C — it’s just the one I typically use for C++.)