https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53281
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Current trunk gives:
cv.cc: In member function ‘void Foo::bar2(const Foo&)’:
cv.cc:4:26: error: passing ‘const Foo’ as ‘this’ argument discards qualifiers
[-fpermissive]
foo.bar1();
^
cv.cc:2:14: note: in call to ‘void Foo::bar1()’
void bar1() {}
^~~~
With this patch:
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -7799,7 +7799,24 @@ build_over_call (struct z_candidate *cand, int flags,
tsubst_flags_t complain)
if (permerror (input_location, "passing %qT as %<this%> "
"argument discards qualifiers",
TREE_TYPE (argtype)))
- inform (DECL_SOURCE_LOCATION (fn), " in call to %qD", fn);
+ {
+ int argquals = cp_type_quals (TREE_TYPE (argtype));
+ int fnquals = cp_type_quals (TREE_TYPE (fn));
+ int discarded = argquals & ~fnquals;
+ bool non_const = discarded & TYPE_QUAL_CONST;
+ bool non_volatile = discarded & TYPE_QUAL_VOLATILE;
+ const char *descr;
+ if (non_const && non_volatile)
+ descr = " which is non-const and non-volatile";
+ else if (non_const)
+ descr = " which is non-const";
+ else if (non_volatile)
+ descr = " which is non-volatile";
+ else
+ descr = "";
+ inform (DECL_SOURCE_LOCATION (fn), " in call to %qD%s",
+ fn, descr);
+ }
}
else
return error_mark_node;
we get:
cv.cc: In member function ‘void Foo::bar2(const Foo&)’:
cv.cc:4:26: error: passing ‘const Foo’ as ‘this’ argument discards qualifiers
[-fpermissive]
foo.bar1();
^
cv.cc:2:14: note: in call to ‘void Foo::bar1()’ which is non-const
void bar1() {}
^~~~
Note the addition of "which is non-const" to the note.
