Check all errors in code?

[vippstar]

How would it break? Even if a macro definition of strtol is provided, it
must also be available as a declaration of an actual function, just like
almost all other standard library functions.

It wouldn't. I realized a bit after I made my post :-(.

 

[vippstar]

No, nobody said it was equivalent. The standard clearly says it's
equivalent *except for the behavior on error*.

You're correct. I didn't notice.

 

[Nick Keighley]

Whilst 0 is a common return value for atoi when its input can't be
represented as an int, the Standard doesn't mandate this, so code that
relies on it is broken.

wow. My first thought was "Richard must be wrong anout this. I'm
certain
atoi() returns zero on error". So I checked. It really is UB if atoi()
cannot perform the conversion! So I learned something new about C
today!