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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 10:29:43 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110617

--- Comment #11 from Florian Weimer <fw at gcc dot gnu.org> ---
(In reply to Xi Ruoyao from comment #10)
> But Zack's reason against using __nonnull is __nonnull may cause unwanted
> optimizations to *the user code*.

GCC already offers options to control function call behavior in the presenc=
e of
nonnull attributes:

     For function calls:
        =E2=80=A2 If the compiler determines that a null pointer is passed =
in an
          argument slot marked as non-null, and the =E2=80=98-Wnonnull=E2=
=80=99 option
          is enabled, a warning is issued.  *Note Warning Options::.
        =E2=80=A2 The =E2=80=98-fisolate-erroneous-paths-attribute=E2=80=99=
 option can be
          specified to have GCC transform calls with null arguments to
          non-null functions into traps.  *Note Optimize Options::.
        =E2=80=A2 The compiler may also perform optimizations based on the
          knowledge that certain function arguments cannot be null.
          These optimizations can be disabled by the
          =E2=80=98-fno-delete-null-pointer-checks=E2=80=99 option.  *Note =
Optimize
          Options::.

So I don't think we need another way to disable nonnull attributes in insta=
lled
glibc headers.=