[Bug c/79775] Confusing fix-it diagnostics with double pointers to structs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79775
--- Comment #3 from felix ---
A particularly amusing variant of this bug occurs with the following code:
struct x { struct x **xx; };
int y = __builtin_offsetof(struct x, xx->xx);
which gives the warning
$ gcc xx.c
xx.c:3:40: error: ‘*0->xx’ is a pointer; did you mean to use ‘->’?
int y = __builtin_offsetof(struct x, xx->xx);
^~
->
mentioning `*0`, which doesn't appear in the source code at all. Similarly for
C++:
$ g++ xx.c
xx.c:3:42: error: request for member ‘xx’ in ‘*((x*)0)->x::xx’, which is of
pointer type ‘x*’ (maybe you meant to use ‘->’ ?)
int y = __builtin_offsetof(struct x, xx->xx);
^~
Compare The Other Compiler, which refuses to parse `->` inside
`__builtin_offsetof` altogether:
$ clang xx.c
xx.c:3:40: error: expected ')'
int y = __builtin_offsetof(struct x, xx->xx);
^
xx.c:3:27: note: to match this '('
int y = __builtin_offsetof(struct x, xx->xx);
^
1 error generated.
I assume GCC parses it in order to have a more user-friendly ‘cannot apply
‘offsetof’ to a non constant address’ error, but I'm not sure if this is worth
it.
[Bug c/79775] Confusing fix-it diagnostics with double pointers to structs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79775
Thomas Schwinge changed:
What|Removed |Added
Last reconfirmed|2017-03-01 00:00:00 |2018-11-7
CC||dmalcolm at gcc dot gnu.org,
||tschwinge at gcc dot gnu.org
--- Comment #2 from Thomas Schwinge ---
I ran into such a thing, too (with today's GCC trunk r265867):
struct s
{
int m;
};
void f(struct s **s)
{
*s->m = 5;
// (*s)->m = 5;
}
C:
../f.c: In function 'f':
../f.c:8:5: error: '*s' is a pointer; did you mean to use '->'?
8 | *s->m = 5;
| ^~
| ->
C++:
../f.c: In function 'void f(s**)':
../f.c:8:7: error: request for member 'm' in '* s', which is of pointer
type 's*' (maybe you meant to use '->' ?)
8 | *s->m = 5;
| ^
[Bug c/79775] Confusing fix-it diagnostics with double pointers to structs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79775 Marek Polacek changed: What|Removed |Added Keywords||diagnostic Status|UNCONFIRMED |NEW Last reconfirmed||2017-03-01 CC||mpolacek at gcc dot gnu.org Ever confirmed|0 |1 --- Comment #1 from Marek Polacek --- Confirmed.
