code review 4634103: cc: add two new #pragma varargck

cc: add two new #pragma varargck

#pragma varargck countpos f 1
says that the first argument to f is
the count of variadic arguments that follow.

#pragma varargck type f t
says that t is one of the allowed types for
a variadic argument to f.
(can be repeated)

combined, these can be used to check the
runtime.stdcall functions in the windows port
or in any other port that needs a vararg list of
uintptrs even on a 64-bit platform (where it is
very easy to pass a less-than-uintptr in the ...).

demo:

typedef unsigned int uintptr;

#pragma varargck countpos f 1
#pragma varargck type f uintptr
#pragma varargck type f void*

int f(int count, ...);

void *v;
char *p;

void
main(void)
{
        f(1, v);  // ok
        f(1, main);  // ok
        f(1, p);  // ok
        f(2, v, v);  // ok

        f(2, v);  // found 1 argument after count 2
        f(1, 'a');  // invalid type INT in call to f
        f(1, 0);  // invalid type INT in call to f
}

[rsc, 2011-06-27 23:49:53]

Hello ken2, r (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg

[r, 2011-06-27 23:53:13]

LGTM

[brainman, 2011-06-28 02:35:42]

LGTM because my change http://codereview.appspot.com/4627071/ works. I'm not
familiar enough with the code.

Thank you anyway.

http://codereview.appspot.com/4634103/diff/3/src/cmd/cc/cc.h
File src/cmd/cc/cc.h (right):

http://codereview.appspot.com/4634103/diff/3/src/cmd/cc/cc.h#newcode825
src/cmd/cc/cc.h:825: 
I don't think you were meant to change this file. ?

http://codereview.appspot.com/4634103/diff/3/src/cmd/cc/dpchk.c
File src/cmd/cc/dpchk.c (right):

http://codereview.appspot.com/4634103/diff/3/src/cmd/cc/dpchk.c#newcode455
src/cmd/cc/dpchk.c:455: if(a->op != OCONST || !typechl[n->type->etype]) {
s/n->type/a->type/

[rsc, 2011-06-28 02:37:31]

http://codereview.appspot.com/4634103/diff/3/src/cmd/cc/cc.h
File src/cmd/cc/cc.h (right):

http://codereview.appspot.com/4634103/diff/3/src/cmd/cc/cc.h#newcode825
src/cmd/cc/cc.h:825: 
On 2011/06/28 02:35:42, brainman wrote:
> I don't think you were meant to change this file. ?

Oops, yeah, that was just me playing.

[rsc, 2011-06-28 02:42:38]

*** Submitted as http://code.google.com/p/go/source/detail?r=18e35543f1af ***

cc: add two new #pragma varargck

#pragma varargck countpos f 1
says that the first argument to f is
the count of variadic arguments that follow.

#pragma varargck type f t
says that t is one of the allowed types for
a variadic argument to f.
(can be repeated)

combined, these can be used to check the
runtime.stdcall functions in the windows port
or in any other port that needs a vararg list of
uintptrs even on a 64-bit platform (where it is
very easy to pass a less-than-uintptr in the ...).

demo:

typedef unsigned int uintptr;

#pragma varargck countpos f 1
#pragma varargck type f uintptr
#pragma varargck type f void*

int f(int count, ...);

void *v;
char *p;

void
main(void)
{
        f(1, v);  // ok
        f(1, main);  // ok
        f(1, p);  // ok
        f(2, v, v);  // ok

        f(2, v);  // found 1 argument after count 2
        f(1, 'a');  // invalid type INT in call to f
        f(1, 0);  // invalid type INT in call to f
}

R=ken, r, alex.brainman
CC=golang-dev
http://codereview.appspot.com/4634103