Amazing: nested function definition in C

[aladdin]

Hi, all

I found that the following code compiles successfully and works well. Does
that mean nested function definition is supported in C just like that in
Pascal?

My compiler is gcc (GCC) 3.3.1 (mingw special 20030804-1).


#include <stdio.h>
#include <stdlib.h>

int foo()
{
int foo1()
{
printf("in foo1\n");
}
printf("in foo\n");
foo1();
}

int main()
{
foo();
system("pause");
}

aladdin

 

[Ben Pfaff]

I found that the following code compiles successfully and works well. Does
that mean nested function definition is supported in C just like that in
Pascal?

No. It's a GCC-only extension.

 

[Artie Gold]

Hi, all

I found that the following code compiles successfully and works well. Does
that mean nested function definition is supported in C just like that in
Pascal?

My compiler is gcc (GCC) 3.3.1 (mingw special 20030804-1).

In GNU C, yes.
In ISO C, *no*.

<ot>
Hint: Try compiling it with the -ansi and -pedantic flags.
</ot>

HTH,
--ag

 

[usr.root]

Hi, all

I found that the following code compiles successfully and works well. Does
that mean nested function definition is supported in C just like that in
Pascal?

My compiler is gcc (GCC) 3.3.1 (mingw special 20030804-1).


#include <stdio.h>
#include <stdlib.h>

int foo()
{
int foo1()
{
printf("in foo1\n");
}
printf("in foo\n");
foo1();
}

int main()
{
foo();
system("pause");
}

aladdin

it's only ok on gcc,even the g++ can not allow to do like that.just
like the first person said:
In GNU C, yes.
In ISO C, *no*.

 

[Martin Ambuhl]

Hi, all

I found that the following code compiles successfully and works well. Does
that mean nested function definition is supported in C just like that in
Pascal?

My compiler is gcc (GCC) 3.3.1 (mingw special 20030804-1).

gcc without switches specifying the standard compiles a language GNUC,
which is not C but very close to it. GNUC supports nested functions, C
does not. The normal gcc implementation comes with documentation about
the horrors associated with implementing this non-standard feature.

 

[Christopher Benson-Manica]

<ot>
Hint: Try compiling it with the -ansi and -pedantic flags.

And lest OP be unaware, -Wall (especially in light of the failure to
return values from functions).

 

[rayw]

Hi, all

I found that the following code compiles successfully and works well. Does
that mean nested function definition is supported in C just like that in
Pascal?

My compiler is gcc (GCC) 3.3.1 (mingw special 20030804-1).


#include <stdio.h>
#include <stdlib.h>

int foo()
{
int foo1()
{
printf("in foo1\n");
}
printf("in foo\n");
foo1();
}

int main()
{
foo();
system("pause");
}

As you've heard - it's a nope. But, a bit of a shame that it's not in ISO
IMHO, as I think it's just a fantastic feature.

 

[Christopher Benson-Manica]

As you've heard - it's a nope. But, a bit of a shame that it's not in ISO
IMHO, as I think it's just a fantastic feature.

The programming world was a different place in 1989, I gather.

 

[Artie Gold]

The programming world was a different place in 1989, I gather.

<OT>
It's not so much the programming world but the systems world for which C
was initially created. Though closures were certainly well known and
well appreciated in 1989 (or 1978, for that matter -- and long before)
they were not in the spirit of a language intended to form a fairly
direct abstraction over assembler. The `spirit' is more along the lines
of `You want a closure? You have the tools to build your own!'

Think also of the mini-computer world of the 'seventies when C was
initially designed. Both cycles and memory were expensive -- as remained
the case in the PC world of the 'eighties as well.

It's a design decision as opposed to being an oversight.
</OT>

HTH,
--ag (who was using closures in Algol a *long* time ago...)

 

[Chuck F.]

The programming world was a different place in 1989, I gather.

Pascal, in 1968, included nested functions. However implementing
such requires some attention to both dynamic and static scope
management. C, being a close to the iron system, doesn't want to
bother with those complications, especially since other mechanisms
(such as multiple files with static declarations) can provide most
of the benefits.