r178975 - Sema: Don't crash when trying to emit a warning for a duplicate value in an invalid enum.

[David Blaikie]

On Sun, Apr 7, 2013 at 7:10 AM, Benjamin Kramer
<benny.kra at googlemail.com> wrote:
> Author: d0k
> Date: Sun Apr  7 09:10:40 2013
> New Revision: 178975
>
> URL: http://llvm.org/viewvc/llvm-project?rev=178975&view=rev
> Log:
> Sema: Don't crash when trying to emit a warning for a duplicate value in an invalid enum.
>
> Fixes PR15693. A null check on a pointer returned from cast<> is a very dubious
> construct, do we have a checker for this somewhere?

Don't think we have much in the way of LLVM-checkers, really.

I've suggested we fix this at compile-time (have cast always return
references, not pointers, since they can't be null anyway (could go
further and have cast/dyn_cast always accept references too, since
they can't be null either)) but people (Chandler) didn't much like
that notion.

>
> Modified:
>     cfe/trunk/lib/Sema/SemaDecl.cpp
>     cfe/trunk/test/Sema/warn-duplicate-enum.c
>
> Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=178975&r1=178974&r2=178975&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaDecl.cpp Sun Apr  7 09:10:40 2013
> @@ -11538,7 +11538,7 @@ static void CheckForDuplicateEnumValues(
>    // Populate the EnumMap with all values represented by enum constants without
>    // an initialier.
>    for (unsigned i = 0; i < NumElements; ++i) {
> -    EnumConstantDecl *ECD = cast<EnumConstantDecl>(Elements[i]);
> +    EnumConstantDecl *ECD = cast_or_null<EnumConstantDecl>(Elements[i]);
>
>      // Null EnumConstantDecl means a previous diagnostic has been emitted for
>      // this constant.  Skip this enum since it may be ill-formed.
>
> Modified: cfe/trunk/test/Sema/warn-duplicate-enum.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/warn-duplicate-enum.c?rev=178975&r1=178974&r2=178975&view=diff
> ==============================================================================
> --- cfe/trunk/test/Sema/warn-duplicate-enum.c (original)
> +++ cfe/trunk/test/Sema/warn-duplicate-enum.c Sun Apr  7 09:10:40 2013
> @@ -90,3 +90,12 @@ enum {
>    NMax = N2,
>    NCount = NMax + 1
>  };
> +
> +// PR15693
> +enum enum1 {
> +  VALUE // expected-note{{previous definition is here}}
> +};
> +
> +enum enum2 {
> +  VALUE // expected-error{{redefinition of enumerator 'VALUE'}}
> +};
>
>
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