Re: allowing a function to be called only from a specific function

CBFalconer wrote:
Harald van D?k wrote:

CBFalconer schreef:
Harald van D?k wrote:
CBFalconer wrote:

... snip ...

Yes it can. The 'static' only prevents visibility outside the
compilation unit.

No, it cannot. f3 is defined before f1 is declared. You can refer
to a static function or variable with an extern declaration if and
only if the a static declaration is already in scope, and you
cannot use static on a function declaration with block scope.

Counter example. Nothing says you have to heed warnings. Proper
isolation requires a separate source file.

[1] c:\c\junk>cat junk.c
#include <stdio.h>

int main(void) {
void f1(void);

f1();
return 0;
} /* main */

static void f1(void) {
puts("In f1");
}

[1] c:\c\junk>cc junk.c
junk.c:10: warning: `f1' was declared `extern' and later `static'

[1] c:\c\junk>.\a
In f1

That's nice. As far as standard C is concerned, the behaviour is
undefined per 6.2.2p7, and my compiler rejects it. If you count
implementation-specific extensions, then inline assembly may also allow
you to access static functions defined in another source file.

Then try this:

#include <stdio.h>
static void f1(void);

int main(void) {

f1();
return 0;
} /* main */

static void f1(void) {
puts("In f1");
}

That's of course allowed, but Chris Dollin's original post of this
subthread already stated that there should be no such forward
declaration. The idea is that main() cannot call f1() without outside
help.

.

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