[llvm-bugs] [Bug 40210] New: c11: Accepts invalid program with incomplete type in generic-association.

via llvm-bugs llvm-bugs at lists.llvm.org
Thu Jan 3 03:04:40 PST 2019


            Bug ID: 40210
           Summary: c11: Accepts invalid program with incomplete type in
           Product: clang
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: anders.granlund.0 at gmail.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk

Test case (prog.c):

  int main()
    _Generic(0, struct S: 1, default: (struct S { int x; }) { 0 } );

Compilation command line:

  clang prog.c -Wall -Wextra -std=c11 -pedantic-errors

Observed behaviour:

  No error messages outputed.

Expected behaviour:

  An error message outputed.

  The type specified by the type-name in the generic-association  struct S: 1
  is not complete yet. It is only completet much later.

  The c standard is not very clear about at what point in the program a type
  needs to be complete when it is used in a context where it is required to be
  complete, but the completion is probably too late here (not complete by the 
  end of the type name, not even by the end of the generic-association).


  GCC gives the expected error message.

  There are alot of other similar differences between GCC and Clang about
  exactly at what point a type needs to be complete. Clang seems to allow the
  completion of a type much later than GCC.

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