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From: "tschwinge at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/114818] New: 'constructor', 'destructor' function attributes
 vs. 'extern'
Date: Tue, 23 Apr 2024 06:28:35 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: diagnostic, documentation
X-Bugzilla-Severity: minor
X-Bugzilla-Who: tschwinge at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114818

            Bug ID: 114818
           Summary: 'constructor', 'destructor' function attributes vs.
                    'extern'
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: diagnostic, documentation
          Severity: minor
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tschwinge at gcc dot gnu.org
  Target Milestone: ---

By chance, I noticed that when 'constructor', 'destructor' function attribu=
tes
appear on an 'extern' function declaration, then that is (a) accepted witho=
ut
any diagnostic by the C, C++ front ends, but (b) no 'constructor', 'destruc=
tor'
calls are emitted.  (Doesn't matter whether the function does or doesn't get
linked in.)

Assuming that is the expected behavior, should we update 'gcc/doc/extend.te=
xi'
for this, and implement a diagnostic (warning or even error, enabled by
default)?

I found that in 'gcc/doc/tm.texi', '@node Initialization' we state:

    [...] Each
    object file that defines an initialization function also puts a word in
    the constructor section to point to that function.  [...]

Note "defines", which excludes 'extern'.=