`inner` declared `static` in `constexpr` context

[llvmbot]

Bugzilla Link	42222
Version	trunk
OS	Linux
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor,@zygoloid

Extended Description

My clang is 9.0.0, and the code is:

struct test { const int *addr; };

const test* setup()
{
 static constexpr test atest =
 {
 ({ static const int inner = 123; &inner; })
 };

 return &atest;
}

int main(){}

clang accepts it, but icc and gcc reject it.

gcc:

source>: In function 'const test* setup()':
<source>:7:22: error: 'inner' declared 'static' in 'constexpr' context
    7 |  ({ static const int inner = 123; &inner; })
      |                      ^~~~~
Compiler returned: 1

icc:

source>(7): error: expression must have a constant value
   ({ static const int inner = 123; &inner; })
    ^
compilation aborted for <source> (code 2)
Compiler returned: 2

[ec04fc15-fa35-46f2-80e1-5d271f2ef708]

Modified example that demonstrates why it might be a good idea to reject this:

struct test { const int *addr; };
int get();               
const test* setup()
{
 static constexpr test atest =
 {
 ({ static int inner = get(); &inner; })
 };

 return &atest;
}

Note that the code generated for setup() does not include a call to get(): we're returning the address of an uninitialized static local.