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From: Jon Turney <>
To: "" <>
Subject: bug with printf positional arguments?
Date: Wed, 28 Jun 2023 14:28:41 +0100	[thread overview]
Message-ID: <> (raw)

The following trivial program (extracted from a glib testcase)

> #include <stdio.h>
> int main()
> {
>   printf ("%1$*2$.*3$s", "abc", 5, 2);
> }

does not produce the expected output of "   ab", on 64-bit Cygwin.

 From a bit of staring at and stepping through get_args() in 
libc/stdio/vfprintf.c, it looks like the problem is (something like) we 
don't have the knowledge that the first positional variadic argument 
should be treated as a pointer, at the point that we store it's value, 
so it gets treated as an integer (the default), which is going to lead 
to truncation on LP64 platforms.

A straightforward way to fix this eludes me.

             reply	other threads:[~2023-06-28 13:28 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-06-28 13:28 Jon Turney [this message]
2023-07-03 11:14 ` Corinna Vinschen
2023-07-03 14:49   ` Jon Turney
2023-07-26 13:26     ` Corinna Vinschen

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