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From: "tromey at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c/47781] warnings from custom printf format specifiers
Date: Mon, 14 Dec 2020 14:10:01 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D47781

--- Comment #24 from Tom Tromey <tromey at gcc dot gnu.org> ---
(In reply to David Crocker from comment #23)
> I need this feature too. Instead of waiting several more years for an
> all-singing all-dancing solution, PLEASE can we have a simple solution th=
at
> allows me to use a custom format specifier and skips a single argument for
> that specifier. I believe this would cover the vast majority of uses cust=
om
> format specifiers. My particular use case is that my application generate=
s a
> lot of JSON strings, so in my printf replacement I want to implement a
> specifier similar to %s that performs JSON escaping on characters in the
> string.

As a workaround, see the kernel doc linked earlier in this bug.
gdb uses this hack as well -- e.g., it uses "%ps" in its formatter
to mean a styled string, passed as a pointer to get past gcc's checking.=