On Sat, 8 Mar 2008 12:21:45 -0600 (CST), Allan Adler
<ara@[EMAIL PROTECTED]
> wrote in comp.lang.c.moderated:
> Suppose the program is:
I wish you would format your code better.
> main() { fn1(); if (debug == 0) fn2();}
This program uses implicit int for the declaration of main, as you
noted, and is a constraint violation under the 1999 and later versions
of the C standard.
> where fn2() returns int and fn1() returns int*. Since main is implicitly
> being declared as returning int, is there a possible problem here? If
> debug does equal 0, then the last thing to execute is fn2, which returns
> the expected int. If debug does not equal 0, then the last thing to
execute
> is fn1() which returns an unexpected int*.
It would have been much better if you had just typed prototypes of
fn1() and fn2() above main(), instead of describing them in words in
the text.
But I don't understand what you are asking.
There is no return statement in main(), which as you noted is
implicitly defined to return an int. That means execution "falls off
the end" of main(), unless fn1() or fn2() call exit() and don't
return.
It makes no difference whether main() calls a function that returns
int, or a function that returns something else, before it falls off
the end. If there is no return statement in main(), than main() does
not return a value, and that means that the exit status returned to
the environment is undefined.
> I am describing a simplification of a piece of code I am reading by
someone
> else.
You seem to think that somehow calling a function returning an int
returns that int value from a containing function, if that is the last
thing the containing function does before hitting its closing brace.
There might be a few compilers that happen to appear to work that way,
perhaps with a specific set of compile-time options. But if so, that
is merely an accident of the code generation that compiler uses for a
specific processor, and is not something standardized by the C
language.
As far as C is concerned, if main(), implicitly or explicitly defined
to return int, ends at its terminating } without executing a return
statement with a value, the exit status returned to the host
environment is undefined. Regardless of what main() does before
hitting the closing brace.
--
Jack Klein
Home: http://JK-Technology.Com
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