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From: "daniel.lundin.mail at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/114266] New: No -pedantic diagnostic for zero-sized array in
 compound literals
Date: Thu, 07 Mar 2024 10:50:44 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114266

            Bug ID: 114266
           Summary: No -pedantic diagnostic for zero-sized array in
                    compound literals
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: daniel.lundin.mail at gmail dot com
  Target Milestone: ---

(int[]){}; produces no diagnostics with -std=3Dc23 -pedantic.

Empty initalizer lists are OK under -std=3Dc23 and -std=3Dgnu so that's not=
 the
problem. gcc correctly gives a diagnostic for that in -std=3Dc17 -pedantic =
mode.

Zero-sized arrays should however give a diagnostic in -std=3Dcxx -pedantic =
mode.
Prior to C23 this was not really a problem as we would get a diagnostic for=
 the
empty initializer list. But now this non-conforming C compiles cleanly even
with -pedantic set.

A diagnostic similar to the one given in clang would be good:
warning: zero size arrays are an extension [-Wzero-length-array]

As I understand it, gcc did have -Wzero-length-array in the past but removed
it? See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94428. The options
-Wstrict-flex-arrays -fstrict-flex-arrays seem to have no effect (and my
example isn't a flexible array member but a compound literal).=