in reply to Re^2: [XS] : "snprintf" portability options
in thread [XS] : "snprintf" portability options

oh-so-thoughtfully re-introduces the issue

No it doesn't. The issue is there with or without the -Wformat. Your sarcasm is misplaced since the warning isn't spurious. The issue is that the wrong format is being used. This is a real error that needs fixing.

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Re^4: [XS] : "snprintf" portability options
by tonyc (Friar) on Sep 16, 2024 at 22:56 UTC

    The warning is spurious, %I64u is valid on Windows. Unfortunately with the macro the full text of the format is hidden so all you have is the misleading "%u" from the base message:

    C:\Users\Tony\dev\perl\git>gcc -Wformat -oint64.exe int64.c
int64.c: In function 'main':
int64.c:6:15: warning: format '%u' expects argument of type 'unsigned 
+int', but argument 2 has type 'long long unsigned int' [-Wformat=]
    6 |   printf("%I64u\n", x);
      |           ~~~~^     ~
      |               |     |
      |               |     long long unsigned int
      |               unsigned int
      |           %I64llu

C:\Users\Tony\dev\perl\git>type int64.c
#include <stdio.h>

unsigned long long x = 0;

int main() {
  printf("%I64u\n", x);
}

    [download]

    If it is a bug, it's a bug in perl, since that's where the macro OP is using comes from.

    I've considered changing the Win32 config in perl to use "%llu"/"%lld" instead, but testing against the older versions of MSVCRT in older Windows that we theoretically support is difficult.

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      If it is a bug, it's a bug in perl

      Don't you mean a bug in gcc? gcc knows it is building for the MS libc, so it should accept the patterns known to work for that libc.

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        I was looking at it from the point of view that the "%I64u" format is incorrect, though it works and perl's own implementation of formatted output emulates it.

        If I could be sure old MSVCRT supported "%llu" I'd make a PR switching it to the standard form, since it would let us turn on -Wformat and better detect format issues on the specialness that is Win32. And reduce confusion from people wondering what this I64 format business is.

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      Bad test. You just repeated what was already said. But replacing 0 with 9223372036854775808ull does make your point.

      So the compiler is wrong about the expected format. wow!

      And thankfully, it still provides the expected format.

      If it is a bug, it's a bug in perl

      It's a bug in gcc. The format expects a unsigned long long, but it claims it expects an unsigned.

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Re^4: [XS] : "snprintf" portability options
by etj (Priest) on Sep 16, 2024 at 13:09 UTC
    jdporter or someone - when I saw the reply in my "chatterbox", it didn't link to my article, but to a node "XS" (a Super Search link). I think that might be a bug?
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      jdporter or someone . . .

      I can see now that we need a "mentions" notification feature. :-/

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        Yes and no.

        Mentions notifications would be nice!

        But bug reports should be collected in Perl Monks Discussion

        For instance I knew you patched the length after our discussion.

        But I wasn't easily able to find neither discussion nor patch.

        Ikegami did the right thing.

        Cheers Rolf
        (addicted to the Perl Programming Language :)
        see Wikisyntax for the Monastery

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        The reply I saw had a SQBRid:// link, but the inner SQBRXS "won", so I hope it's solved properly with that second go.
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        Test bug anonymously by lanx
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        Test after patch committed by lanx
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