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From: "fw at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/110617] RFE: Add a diagnostic-only variant of
 nonnull attribute
Date: Tue, 11 Jul 2023 09:10:11 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110617

--- Comment #9 from Florian Weimer <fw at gcc dot gnu.org> ---
(In reply to Xi Ruoyao from comment #6)
> (In reply to Richard Biener from comment #5)
> > I think a -f... option to disable the code generation effects would make
> > more sense than adding another attribute kind.
>=20
> Then maybe we'd just add a -D_GLIBC_NONNULL=3D{0,1} (?) into Glibc cdefs.h
> instead.  Anyway I'm already too frustrated about this so I'll not contin=
ue
> working on nonnull within Glibc headers.  If you don't like this just clo=
se
> it as WONTFIX.

For those who are not following libc-alpha, glibc already disables __nonnull
during its build, so it should be totally fine to use __nonnull in installed
headers to improve diagnostics.

We have this in include/sys/cdefs.h (which augments <sys/cdefs.h>):

/* The compiler will optimize based on the knowledge the parameter is
   not NULL.  This will omit tests.  A robust implementation cannot allow
   this so when compiling glibc itself we ignore this attribute.  */
# undef __nonnull
# define __nonnull(params)

We'd like the diagnostics for building glibc itself, and a new -f option wo=
uld
help with that.=