C/C++: add fix-it hints for missing '&' and '*' (v5) [PR87850]

This patch adds a note with a fix-it hint to various
pointer-vs-non-pointer diagnostics, suggesting the addition of
a leading '&' or '*'.

For example, note the ampersand fix-it hint in the following:

demo.c: In function 'int main()':
demo.c:5:22: error: invalid conversion from 'pthread_key_t' {aka 'unsigned int'}
   to 'pthread_key_t*' {aka 'unsigned int*'} [-fpermissive]
    5 |   pthread_key_create(key, NULL);
      |                      ^~~
      |                      |
      |                      pthread_key_t {aka unsigned int}
demo.c:5:22: note: possible fix: take the address with '&'
    5 |   pthread_key_create(key, NULL);
      |                      ^~~
      |                      &
In file included from demo.c:1:
/usr/include/pthread.h:1122:47: note:   initializing argument 1 of
   'int pthread_key_create(pthread_key_t*, void (*)(void*))'
 1122 | extern int pthread_key_create (pthread_key_t *__key,
      |                                ~~~~~~~~~~~~~~~^~~~~

gcc/c-family/ChangeLog:
	PR c++/87850
	* c-common.cc: Include "gcc-rich-location.h".
	(maybe_emit_indirection_note): New function.
	* c-common.h (maybe_emit_indirection_note): New decl.
	(compatible_types_for_indirection_note_p): New decl.

gcc/c/ChangeLog:
	PR c++/87850
	* c-typeck.cc (compatible_types_for_indirection_note_p): New
	function.
	(convert_for_assignment): Call maybe_emit_indirection_note for
	pointer vs non-pointer diagnostics.

gcc/cp/ChangeLog:
	PR c++/87850
	* call.cc (convert_like_real): Call maybe_emit_indirection_note
	for "invalid conversion" diagnostic.
	* typeck.cc (compatible_types_for_indirection_note_p): New
	function.

gcc/testsuite/ChangeLog:
	PR c++/87850
	* c-c++-common/indirection-fixits.c: New test.
	* g++.dg/template/error60.C: Add fix-it hint to expected output.
	* g++.dg/template/error60a.C: Likewise.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>

1 files changed, 16 insertions, 2 deletions

diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index f465123..e429ce9 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -1438,6 +1438,14 @@ struct comptypes_data {
   const struct tagged_tu_seen_cache* cache;
 };
 
+/* C implementation of compatible_types_for_indirection_note_p.  */
+
+bool
+compatible_types_for_indirection_note_p (tree type1, tree type2)
+{
+  return comptypes (type1, type2) == 1;
+}
+
 /* Return 1 if TYPE1 and TYPE2 are compatible types for assignment
    or various other operations.  Return 2 if they are compatible
    but a warning may be needed if you use them together.  */
@@ -8487,7 +8495,10 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
 	      if (permerror_opt (&richloc, OPT_Wint_conversion,
 				 "passing argument %d of %qE makes pointer "
 				 "from integer without a cast", parmnum, rname))
-		inform_for_arg (fundecl, expr_loc, parmnum, type, rhstype);
+		{
+		  maybe_emit_indirection_note (expr_loc, rhs, type);
+		  inform_for_arg (fundecl, expr_loc, parmnum, type, rhstype);
+		}
 	    }
 	    break;
 	  case ic_assign:
@@ -8527,7 +8538,10 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
 	    if (permerror_opt (&richloc, OPT_Wint_conversion,
 			       "passing argument %d of %qE makes integer from "
 			       "pointer without a cast", parmnum, rname))
-	      inform_for_arg (fundecl, expr_loc, parmnum, type, rhstype);
+	      {
+		maybe_emit_indirection_note (expr_loc, rhs, type);
+		inform_for_arg (fundecl, expr_loc, parmnum, type, rhstype);
+	      }
 	  }
 	  break;
 	case ic_assign: