Re: [idea] request_module(const char *fmt, ...);

From: willy tarreau (wtarreau@yahoo.fr)
Date: Fri Jan 14 2000 - 07:16:53 EST

Hi guys,

I think I have a solution to the variable-length macro
:

if you define an empty macro for request_module, this
line :

   request_module("blah","blah2","foobar");

will be converted to :

   ("blah","blah2","foobar");

which is treated by the compiler as useless code and
will no even generate one byte of code.

Here is a looser example which works :

#ifndef ENABLE

#define test_func

#else

#define test_func myfunc

int myfunc(char *fmt, ...) {
  return *fmt;
}

#endif

main() {
  test_func("azerazer","aerazerazer");
}

when compiled with gcc -S -O2 -DENABLE, you'll get
this output :

.text
        .align 4
.globl myfunc
        .type myfunc,@function
myfunc:
        pushl %ebp
        movl %esp,%ebp
        movl 8(%ebp),%eax
        movsbl (%eax),%eax
        leave
        ret
.Lfe1:
        .size myfunc,.Lfe1-myfunc
.section .rodata
.LC0:
        .string "aerazerazer"
.LC1:
        .string "azerazer"
.text
        .align 4
.globl main
        .type main,@function
main:
        pushl %ebp
        movl %esp,%ebp
        pushl $.LC0
        pushl $.LC1
        call myfunc
        leave
        ret

But when compiled with gcc -O2 -S test.c, you get this
shorter code :

.text
        .align 4
.globl main
        .type main,@function
main:
        pushl %ebp
        movl %esp,%ebp
        leave
        ret

I think this is perfectly usable, any comments ?

Willy

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This archive was generated by hypermail 2b29 : Sat Jan 15 2000 - 21:00:24 EST