Hello,
Consider the following test case:
struct A { bool g(int*, int*) __attribute__((nonnull (2))); };
bool A::g(int* a, int* b) {
if (a)
return 0;
return this;
}
G++ produces the following code for this snippet:
;; Function bool A::g(int*, int*) (_ZN1A1gEPiS0_)
bool A::g(int*, int*) (this, a, b)
{
<bb 2>:
return 0;
}
Notice how we have applied the __attribute__((nonnull (2))) to
the "a" argument, instead of "b", because G++ has added "this"
as an extra, artificial argument. To the middle end, argument 2
of "g" is "a", not "b".
The documentation of the nonnull attribute says:
`nonnull (ARG-INDEX, ...)'
The `nonnull' attribute specifies that some function parameters
should be non-null pointers. For instance, the declaration:
extern void *
my_memcpy (void *dest, const void *src, size_t len)
__attribute__((nonnull (1, 2)));
causes the compiler to check that, in calls to `my_memcpy',
arguments DEST and SRC are non-null.
So do we expect our users to know that they should add 1 to every
ARG-INDEX they pass? That would make this a documentation bug. Or
is this a "real" bug in G++, and should the compiler correct the
ARG-INDEX numbers so that the middle-end doesn't get confused?
Gr.
Steven
