https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103363
Bug ID: 103363
Summary: confusing -Wnonnull-compare testing a reference
argument for equality to null
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
Since the conversion of the address of a reference to bool is diagnosed by
-Waddress, issuing a second warning for it isn't necessary. Mentioning
attribute nonnull where there is one in the source code seems confusing.
$ cat t.C && gcc -O2 -S -Wall t.C
struct S { int i; };
bool f (const S &s)
{
return &s;
}
t.C: In function ‘bool f(const S&)’:
t.C:5:10: warning: the compiler can assume that the address of ‘s’ will never
be NULL [-Waddress]
5 | return &s;
| ^~
t.C:3:18: note: ‘s’ declared here
3 | bool f (const S &s)
| ~~~~~~~~~^
t.C:5:11: warning: ‘nonnull’ argument ‘s’ compared to NULL [-Wnonnull-compare]
5 | return &s;
| ^
Clang issues just one warning (though the wording doesn't seem ideal either:
there's no evidence of dereferencing a null pointer so assuming that's what
necessarily led the programmer to the test doesn't seem warranted):
warning: reference cannot be bound to dereferenced null pointer in well-defined
C++ code; pointer may be assumed to always convert to true
[-Wundefined-bool-conversion]
return &s;
