Re: typedefs and structs

[J.A. Magallon]

On Thu, 10 Nov 2005 11:28:27 -0800 (PST), Vadim Lobanov <vlobanov@xxxxxxxxxxxxx> wrote:

> On Thu, 10 Nov 2005, Kyle Moffett wrote:
> 
> > On Nov 10, 2005, at 08:27:18, Nikita Danilov wrote:
> > > extern declaration in your version of bar() cannot refer to the
> > > automatic variable myvar in foo().
> >
> > int foo;
> 
> Except foo is not an automatic variable within show(). When the variable
> is global, then there's no argument. It was a question of when foo is
> local and bar() would get a const pointer to the local.
> 
> > void bar(const int *local_var) {
> >      foo = *local_var + 1;
> > }
> >
> > void show(void) {
> >      printf("%d\n", foo);
> >      bar(&foo);
> >      printf("%d\n", foo);
> > }
> >

You can tweak it all as you want:

int* foo_p;

void bar(const int *local_var) {
  *foo_p = *local_var + 1;
}

int main() {
  int foo;
  foo_p = &foo;
  printf("%d\n", foo);
  bar(&foo);
  printf("%d\n", foo);

  return 0;
}

The fact is that gcc can't suppose anything unless you say explicitly it can.
That is why 'pure' and 'const' __attributes__ exist, it supposes aliasing
by default and so on.

--
J.A. Magallon <jamagallon()able!es>     \               Software is like sex:
werewolf!able!es                         \         It's better when it's free
Mandriva Linux release 2006.1 (Cooker) for i586
Linux 2.6.14-jam1 (gcc 4.0.2 (4.0.2-1mdk for Mandriva Linux release 2006.1))

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