FILE* ... perl 5.6 ... backwards compatibility

syphilis has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

The script:

use Inline C => Config =>
    CLEAN_AFTER_BUILD => 1,
    BUILD_NOISY => 1;

use Inline C => <<'EOC';

SV * foo(FILE * stream) {
     return newSVuv(42);
}

EOC

print foo(*STDOUT);
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Running on perl 5.6 I get the following warning during compilation:

try_pl_0446.c: In function `XS_main_foo':
try_pl_0446.c:28: warning: initialization from incompatible pointer ty
+pe
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Looking at the C file I see that line 28 is:

FILE *    stream = IoIFP(sv_2io(ST(0)));
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The same script, run under perl 5.8 produces no compiler warnings. The corresponding line in the C file is:

FILE *    stream = PerlIO_findFILE(IoIFP(sv_2io(ST(0))));
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(Note that in both instances the C file was autogenerated by ExtUtils::ParseXS version 2.17.)

Questions:
1) Is there anything I can do to remove that warning with perl 5.6 ?
2) Should I be perturbed by the warning issued with perl 5.6 ?

It's unlikely that the actual demo I've provided is going to suffer from the "incompatible pointer" ... but in the real world, foo() actually *does* something with the FILE* argument. So far, it all seems to work as intended ... but compiler warnings always worry me ...

Cheers,
Rob

Comment on FILE* ... perl 5.6 ... backwards compatibility Select or Download Code

Replies are listed 'Best First'.
Re: FILE* ... perl 5.6 ... backwards compatibility by BrowserUk (Patriarch) on Dec 05, 2007 at 13:03 UTC
I no longer have 5.6.1 to test, but does using `\*STDOUT` help? Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l]
Re^2: FILE* ... perl 5.6 ... backwards compatibility by syphilis (Archbishop) on Dec 06, 2007 at 00:27 UTC
As with perl 5.8, the presence (or absence) of the backslash seems to make no difference at all. (Note that, in any case, it won't have any effect on the actual warnings I quoted - as they occur during the compilation of the C code, long before any arguments actually get passed to `foo`.) I was curious to see what happened on linux with 5.6, but `make` didn't like the makefile that Configure created and I quickly lost interest in building perl 5.6 on my linux box. I'll assume the warnings are benign ... until evidence to the contrary presents itself. Cheers, Rob	[reply] [d/l] [select]