Suppress -Wlto-type-mismatch warning for struct with flexible array

Question

I'm doing a gcc compile with -Wlto-type-mismatch and -Werror set (for the good of the rest of the project). I have an extern struct with a flexible array that is provoking an lto-type-mismatch warning/error.

Here's the code distilled down to an example:

h.h:

typedef struct {
  int i;
  int ints[];
} struct_t;

a.c:

#include "h.h"

extern struct_t my_struct;

int main() {  // just here to avoid optimizing away the decls
  return my_struct.ints[0];
}

b.c:

#include "h.h"

struct_t my_struct = {
  20,
  {
    1,
    2,
  },
};

Compiling (using arm gcc here, but it also fails with native gcc)

$ arm-none-eabi-gcc -flto -Wlto-type-mismatch -Werror a.c b.c -o foo
a.c:3:17: error: size of 'my_struct' differ from the size of original declaration [-Werror=lto-type-mismatch]
 extern struct_t my_struct;
                 ^
b.c:3:10: note: 'my_struct' was previously declared here
 struct_t my_struct = {
          ^
lto1: all warnings being treated as errors

I've tried wrapping one or both of the declarations in

#pragma gcc diagnostic push
#pragma gcc diagnostic ignore "-Wlto-type-mismatch"
<decl>
#pragma gcc diagnostic pop

but I can't suppress the warning, possibly because it is a link-time optimization and the #pragma lines are long gone at that point.

Question

Can you suggest some way to get this to compile and still preserve the warning elsewhere? (Or should -Wlto-type-mismatch not be complaining about the flexible array? If so, I can submit a bug report.)

Answer 1

After inquiring on gcc-help mailing list, I submitted a bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81440. Will follow up here when something happens.]

Followup: the bug has been fixed as of gcc 7.3.1 or earlier.