getc() vs fgetc() - What are the major differences?

Question

Everywhere I see \"it is practically identical\", or something similar...

From The GNU C Programming Tutorial :

There is another function in t

Answer 1

There are essentially the same (or similar enough to not bother). You should look at their implementation: GNU libc and MUSL libc are free software implementations. And they now could be implemented as inline functions (which are as fast as macros).

And I won't bother that much. In real life, I/O is mostly constrained by hardware (e.g. the time to access the disk).

Answer 2

From the Advanced Programming in Unix Environment:

...

The difference between getc and fgetc is that getc can be implemented as a macro, whereas fgetc cannot be implemented as a macro. This means three things:

• The argument to getc should not be an expression with side effects.
• Since fgetc is guaranteed to be a function, we can take its address. This allows us to pass the address of fgetc as an argument to another function.
• Calls to fgetc probably take longer than calls to getc, as it usually takes more time to call a function.

...

Answer 3

Seems like the differences are, in 99.9% of the cases, meaningless.

One point which may make a difference - The man page says getc() may be implemented as a macro which evaluates stream more than once.

It could lead to strange behavior in some (not very useful) cases, e.g.:

FILE *my_files[10] = {...}, *f=&my_files[0];
for (i=0; i<10; i++) {
    int c = getc(f++);    // Parameter to getc has side effects!
}

If getc evaluates f++ more than once, it will advance f more than once per iteration. In comparison, fgetc is safe in such situations.