Weird gcc behaviour with function pointer types

[attn.steven.kuo at gmail.com]

On Mar 29, 6:05 am, greg <g... at cosc.canterbury.ac.nz> wrote:
> In my quest to eliminate C compiler warnings from
> Pyrex output, I've discovered some utterly bizarre
> behaviour from gcc 3.3.
>
> The following code:
>
>    void g(struct foo *x) {
>    }
>
>    void f(void) {
>      void (*h)(struct foo *);
>      h = g;
>    }
>
> produces the following warning:
>
>    blarg.c: In function `f':
>    blarg.c:6: warning: assignment from incompatible pointer type
>
> However, adding the following line at the top:
>
>    typedef struct foo Foo;
>
> makes the warning go away. The mere *presence* of
> the typedef is all that's needed -- it doesn't even
> have to be used.
>
> This looks like a bug in gcc to me -- what do people
> think?



Was there no (forward) declaration nor
definition of struct foo ahead of your functions?

I get no warnings with this:


struct foo; /* forward declaration */

void g(struct foo *x) {
}

void f(void) {
    void (*h)(struct foo *);
    h = g;
}


Using:

Target: powerpc-apple-darwin8
Configured with: /private/var/tmp/gcc/gcc-5026.obj~19/src/configure --
disable-checking --prefix=/usr --mandir=/share/man --enable-
languages=c,objc,c++,obj-c++ --program-transform-name=/^[cg][^+.-]*$/s/
$/-4.0/ --with-gxx-include-dir=/include/gcc/darwin/4.0/c++ --
build=powerpc-apple-darwin8 --host=powerpc-apple-darwin8 --
target=powerpc-apple-darwin8
Thread model: posix

gcc version 4.0.0 (Apple Computer, Inc. build 5026)

--
Hope this helps,
Steven