[Bug c/65471] type interpretation in _Generic

[wink at saville dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65471

Wink Saville <wink at saville dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |wink at saville dot com

--- Comment #3 from Wink Saville <wink at saville dot com> ---
Tested on on gcc 5.3.0 on an x86_64 Arch Linux machine.

When using bit field as a selector _Generic uses the default path
and in the following test program outputs "unknown":

$ cat test.c

$ cat test.c
#include <stdio.h>

struct S {
  int b0:4;
  unsigned int b1:4;
  unsigned long long int b33:33;
};

#define type2str(__x) _Generic((__x), \
  int : "int", \
  unsigned int : "unsigned int", \
  unsigned long long int : "unsigned long long int", \
  default : "unknown")

int main(void) {
  struct S s = { .b0=3, .b1=4, .b33=0x1FFFFFFFF };
  (void)s; // Not used

                                                   // gcc     | clang output
  printf("type2str(s.b0):  %s\n", type2str(s.b0)); // unknown | int
  printf("type2str(s.b1):  %s\n", type2str(s.b1)); // unknown | unsigned int
  printf("type2str(s.b33): %s\n", type2str(s.b33));// unknown | unsigned long
long int

  return 0;
}

$ cat Makefile 
CC = gcc
O = 3
STD = c11
M = 32

test: test.c Makefile
        $(CC) -O$(O) -m$(M) -Wall -std=$(STD) test.c -o test

clean:
        rm -f test


$ make clean ; make CC=gcc ; ./test
rm -f test
gcc -O3 -m32 -Wall -std=c11 test.c -o test
type2str(s.b0):  unknown
type2str(s.b1):  unknown
type2str(s.b33): unknown

$ make clean ;make CC=clang ; ./test
rm -f test
clang -O3 -m32 -Wall -std=c11 test.c -o test
type2str(s.b0):  int
type2str(s.b1):  unsigned int
type2str(s.b33): unsigned long long int


Additional discussion on gcc thread:
https://gcc.gnu.org/ml/gcc/2016-02/msg00255.html