[Bug c++/87504] New: inconsistent diagnostic style between C and C++

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87504

            Bug ID: 87504
           Summary: inconsistent diagnostic style between C and C++
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

I noticed an improvement in the diagnostic GCC issues for the following test
case (where I made a typo in the first argument to strlnen: a&a[v0]).

$ cat c.c && gcc -O2 -S -fdump-tree-optimized=/dev/stdout c.c
const char a[] = "12345"; 

int v0 = 0;

int f (unsigned n)
{
  if (n < 6)
    n = 6;

  return __builtin_strnlen (a&a[v0], n);
}

c.c: In function ‘f’:
c.c:10:30: error: invalid operands to binary & (have ‘const char *’ and ‘int’)
10 |   return __builtin_strnlen (a&a[v0], n);
   |                             ~^~~~~~
   |                             |  |
   |                             |  char
   |                             const char *


But when testing the same code with G++ I also noticed the message is slightly
different:

c.c: In function ‘int f(unsigned int)’:
c.c:10:30: error: invalid operands of types ‘const char [6]’ and ‘const char’
to binary ‘operator&’
10 |   return __builtin_strnlen (a&a[v0], n);
   |                             ~^~~~~~


It would be nice to converge on the same format and phrasing of the diagnostic
between the two languages.

FWIW, although I like how the C message distinguishes the operands from the
operator using different colors rendering each of the operands in its own color
seems somewhat distracting (it raises the question: do the colors suggest some
subtlety of the error that's not captured in the text?)  I also find the C++
phrasing more readable than the C style with the "(have ‘const char *’ and
‘int’)".