[usrbinbash]

Whether the program fails or not, is a matter of specification.

    printf("Hello, World!\n")

Is me saying: "Do a write syscall to stdout. I don't care what the return value is, I don't care if the flush is successfull if stdout happens to be buffered." If that is what I want to do, aka. what the program is specified to do, then it didn't fail.

[ryandrake]

To me, your example says: "I forgot about the return value." The way I learned C, if you really, really want to say "I don't care what the return value is" you'd explicitly cast it, nicely documenting your active non-caring about the return value for future code readers:

    (void) printf("Hello, World!\n");

Although, in general, ignoring the return value from things like puts() and printf() is a bad idea, for reasons the article makes clear.

[usrbinbash]

And how do I explicitly ignore the other ways C communicates error conditions, like global error variables (eg. errno), inbound error values, errflags in structs?