Clang -Wunused-const-variable in C vs. C++

Question

A file with just a const declaration, like so:

const int genericRC = 0;

when compiled with the clang C++ front end warns about this unused variable. However, the clang C front end is silent about this:

$ cat x.sh
clang   -c src/x.c   -Wall -std=c11
clang++ -c src/t.cpp -Wall -std=c++11

$ ./x.sh
src/t.cpp:1:11: warning: unused variable 'genericRC' [-Wunused-const-variable]
const int genericRC = 0;
          ^
          1 warning generated.

Is there any fundamental difference in C vs. C++ const for const static scoped variables of this sort, or is this just a warning that happens to be implemented in the clang C++ front end, but not in the C front end.

Answer 1

In C++ this has internal linkage so the compiler can know it is unused. In C it has external linkage so it might be used from another translation unit, therefore it would be premature to warn.