Void main() issue

[ozumsafa]

I have been reading why void main() is bad , and I have seen a line ;

>(void)fgets(buf, 1024, stdin);

What does that void at the beginning mean?

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Also , The wiriting was mentioning that library startup code always need a return value. If the main is void , it will take the return value from another component. Depending on what the compiler chooses that value? Or is there really a value or am I wrong?

Thank you.

[QuantumPete]

>(void)fgets(buf, 1024, stdin);

This will cast away the value returned by fgets. In essence, you're telling the compiler that you know better, that fgets doesn't return anything you're interested in and that it should shut up about it. No idea whay you'd want to do that.

QuantumPete

[Prelude]

>What does that void at the beginning mean?
It says that you really aren't using the return value and you don't want to see any warnings. I think it's clutter, but some lint programs will warn you about unused return values on their most persnickety setting.

>The wiriting was mentioning that library startup code always need a return value. If the main
>is void , it will take the return value from another component. Depending on what the
>compiler chooses that value? Or is there really a value or am I wrong?
That sounds like a weak argument, but I don't think you described it well enough for me to be sure.

[robatino]

> some lint programs will warn you about unused return values on their most persnickety setting.

Yes, I remember trying lint a long time ago and it would throw off warnings whenever you used printf() without casting it to void (which was needed about 99.99% of the time).

[matsp]

>The wiriting was mentioning that library startup code always need a return value. If the main
>is void , it will take the return value from another component. Depending on what the
>compiler chooses that value? Or is there really a value or am I wrong?
That sounds like a weak argument, but I don't think you described it well enough for me to be sure.

Casting the return value from another function will not change what the called function does, and it's the called function that "issues" the return value (e.g. it puts some value in EAX in common x86 code). If you omit the return from main (or make it void), the "return value" will be whatever is in EAX (or the relevant return register in other architectures). If your code ends with a getchar() and someone presses 'A', the return value will be 65 (most likely - it is possible that it gets "lost" somehwere - try it if you like...).

Note that if you have no return statement in main, and the last bit of main is some function call that is has a void return or some calculations, the return value will be some unpredictabel value [as in unpredictable without examining the generated assembler code and knowing what happens in that code - and this will change if you modify the source, change the compiler settings or use a different compiler for example].

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Mats