Ping: https://gcc.gnu.org/pipermail/gcc-patches/2020-June/547415.html
Jason already approved the C++ changes (with a couple of minor
tweaks). I'm still looking for an approval of the corresponding
middle end diff.
On 6/5/20 1:41 PM, Martin Sebor wrote:
The caret location C++ -Wnonnull warnings is in the wrong place:
either under the closing parenthesis of a call to a function
declared nonnull, or under the whole call (when issued from
the middle end). In addition, for member functions, the one-based
argument number mentioned in the warning starts with the implicit
this pointer, while in non-members it starts with the first argument.
That makes it difficult to tell which argument the warning is
complaining about (see the test + output below).
The attached patch improves things in a few minor ways:
1) by using the argument location when it has one to underline it
(the location isn't always available at this point but that
can be improved in a followup)
2) by using 1 for the first explicit argument, and by mentioning
'this' for the this pointer
3) by changing the message issued by the front-end (and the C++
member function handling) to match the corresponding message
(and handling) in the middle end.
Finally, the patch also arranges to treat the C++ this pointer
as implicitly nonnull, regardless of whether the member function
is declared with the attribute.
Tested on x86_64-linux.
Martin
PS For this test case:
__attribute__ ((nonnull)) void f (const char*);
struct S
{
__attribute__ ((nonnull)) void g (const char*) const;
};
void g (void)
{
{
const char* const null = 0;
f (null);
}
{
const S* const null = 0;
null->g ("");
}
}
GCC trunk outputs:
t.C: In function ‘void g()’:
t.C:12:12: warning: null argument where non-null required (argument 1)
[-Wnonnull]
12 | f (null);
| ^
t.C:17:16: warning: null argument where non-null required (argument 1)
[-Wnonnull]
17 | null->g ("");
| ^
With the patch the output is:
t.C: In function ‘void g()’:
t.C:12:8: warning: argument 1 null where non-null expected [-Wnonnull]
12 | f (null);
| ^~~~
t.C:1:32: note: in a call to function ‘void f(const char*)’ declared
‘nonnull’
1 | __attribute__ ((nonnull)) void f (const char*);
| ^
t.C:17:5: warning: ‘this’ pointer null [-Wnonnull]
17 | null->g ("");
| ^~~~
t.C:5:34: note: in a call to non-static member function ‘void S::g(const
char*) const’
5 | __attribute__ ((nonnull)) void g (const char*) const;
| ^
