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Re: your malloc patches

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Jarkko Hietaniemi
July 19, 2005 00:14
Re: your malloc patches
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Joshua Hoblitt wrote:
> On Sun, Jun 15, 2003 at 09:14:16PM +0300, Jarkko Hietaniemi wrote:
>>>>This just isn't cricket for non-GCC compilers (Solaris, AIX, and Tru64
>>>>claim a syntax error, IRIX seems to tolerate it).  That a function
>>>>call (Perl_doing_taint in this case) gets expanded to func(a,b,) just
>>>>isn't going to work.  (What does leaving out an argument like that
>>>>_mean_, anyway?  An implicit 0?)
>>>It is a *macro*, not a function call!  Macros operate on strings.  An
>>>empty string is a perfectly valid string (though I do not know what
>>When the macro gets expanded at the very beginning of main() we get this:
>>	if (Perl_doing_taint(*&argc, *&argv, ))
>>which makes many C compilers to choke, but apparently not gcc.
>>>the C standard says on this).
>>>Anyway, this slot is not used, so put there NOTUSED.
>>I have no idea what you mean by NOTUSED.  If you mean the trick you said:
>>#define NOTUSED
>>#define MALLOC_CHECK_TAINT2(argc,argv)  MALLOC_CHECK_TAINT(argc,argv,NOTUSED)
>>That doesn't work since that gets expanded to exactly the same as above.
> A possible solution would be to use __VA_ARGS__.  I'm not sure how
> portable this is between cpp implementations... it supposedly has worked
> with gcc since at least 2.95 (I haven't tried it with anything older
> than gcc 3.3) and it is part of C99.

Perl sources are C89 compliant and generally try to stay so (i.e. not
introduce C99-isms, at least not unconditionally so).  But thanks for
the information, that may turn out to be useful for something else.

> #define MALLOC_CHECK_TAINT2(argc,...) MALLOC_CHECK_TAINT(argc,__VA_ARGS__)

It was two years ago :-) but I think, based on the current perl.h,
that we just opted for assuming that the third argument to main while
non-standard is at least tolerated widely enough:

#define MALLOC_CHECK_TAINT2(argc,argv)  MALLOC_CHECK_TAINT(argc,argv,NULL)

> --

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