[PATCH] D125259: [C11] Diagnose unreachable generic selection associations

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

In D125259#3519822 <https://reviews.llvm.org/D125259#3519822>, @aeubanks wrote:

>   $ cat /tmp/a.cc
>   typedef struct Test {
>   } Test;
>   
>   void f() {
>     const Test constVal;
>     _Generic(constVal, const Test : 0);
>   }
>   $ ./build/rel/bin/clang -fsyntax-only  -x c++ /tmp/a.cc -Wall
>   /tmp/a.cc:6:28: warning: due to lvalue conversion of the controlling expression, association of type 'const Test' will never be selected because it is qualified [-Wunreachable-code-generic-assoc]
>     _Generic(constVal, const Test : 0);
>                              ^
>   /tmp/a.cc:6:35: warning: expression result unused [-Wunused-value]
>     _Generic(constVal, const Test : 0);
>                                     ^
>   2 warnings generated.
>   $ ./build/rel/bin/clang -fsyntax-only  -x c /tmp/a.cc -Wall
>   /tmp/a.cc:6:28: warning: due to lvalue conversion of the controlling expression, association of type 'const Test' (aka 'const struct Test') will never be selected because it is qualified [-Wunreachable-code-generic-assoc]
>     _Generic(constVal, const Test : 0);
>                              ^
>   /tmp/a.cc:6:12: error: controlling expression type 'Test' (aka 'struct Test') not compatible with any generic association type
>     _Generic(constVal, const Test : 0);
>              ^~~~~~~~
>   1 warning and 1 error generated.
>
> the C++ case looks wrong, it's warning that `const Test` can't be selected then selects it

Oh wow, good catch! I'll correct this.


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https://reviews.llvm.org/D125259