function declarations

[conrad]

Where in the standard does it say that the following
definition of foo():

void foo(void)
{
baz();
}

int main(void)
{
foo();
return 0;
}


acts as both a declaration and a definition but only
when it precedes the main function?

 

[Eric Sosman]

Where in the standard does it say that the following
definition of foo():

void foo(void)
{
baz();
}

int main(void)
{
foo();
return 0;
}


acts as both a declaration and a definition but only
when it precedes the main function?

Nowhere. There's nothing special about main() in this
regard.

A definition is always a declaration (but some declarations
are not definitions). Most identifiers must be declared before
they are used; it doesn't much matter whether they are declared
by a definition or by a non-defining declaration.

See section 6.2.1 (especially paragraphs 2 and 4) for the
requirements that boil down to "declare before using."