[Bug c/102821] New: Tentative definition of variable with internal linkage has incomplete non-array type: missing diagnostics

[Bug c/102821] New: Tentative definition of variable with internal linkage has incomplete non-array type: missing diagnostics

[pavel.morozkin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102821

            Bug ID: 102821
           Summary: Tentative definition of variable with internal linkage
                    has incomplete non-array type: missing diagnostics
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pavel.morozkin at gmail dot com
  Target Milestone: ---

Sample code (t940.c):
static struct s foo;
static struct s {int a;} foo;

Invocation:
$ gcc t940.c -c -std=c11 -pedantic -Wall -Wextra -Wno-unused-variable

Expected diagnostics:
t940.c:1:17: warning: tentative definition of variable with internal linkage
has incomplete non-array type 'struct s'
[-Wtentative-definition-incomplete-type]

Actual diagnostics:
<nothing>

Notes:
1. C11, 6.9.2 External object definitions, 3:
> If the declaration of an identifier for an object is a tentative definition and has internal linkage, the declared type shall not be an incomplete type.

2. C11, 4. Conformance, 1:
> In this International Standard, ‘‘shall’’ is to be interpreted as a requirement on an implementation or on a program; conversely, ‘‘shall not’’ is to be interpreted as a prohibition.

[Bug c/102821] Tentative definition of variable with internal linkage has incomplete non-array type: missing diagnostics

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102821

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-10-18
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

[Bug c/102821] Tentative definition of variable with internal linkage has incomplete non-array type: missing diagnostics

[pavel.morozkin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102821

--- Comment #2 from Pavel M <pavel.morozkin at gmail dot com> ---
Addition to "Notes" above.

3. C11, 5.1.1.3 Diagnostics, 1:
> A conforming implementation shall produce at least one diagnostic message (identified in an implementation-defined manner) if a preprocessing translation unit or translation unit contains a violation of any syntax rule or constraint, even if the behavior is also explicitly specified as undefined or implementation-defined.

[Bug c/102821] Tentative definition of variable with internal linkage has incomplete non-array type: missing diagnostics

[jsm28 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102821

Joseph S. Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|NEW                         |RESOLVED

--- Comment #3 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
This is in a Semantics section of the standard, not Constraints, so no
diagnostic is required, but as a quality-of-implementation matter we should
diagnose it.

*** This bug has been marked as a duplicate of bug 88727 ***