https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86878
Bug ID: 86878
Summary: G++ should warn about invalid alignments passed to
allocation functions
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: enhancement
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
#include <new>
__attribute__ ((__alloc_align__(2)))
void* alloc(std::size_t, std::size_t);
int main()
{
(void) alloc(10, 5);
(void) ::operator new(10, std::align_val_t{5});
}
This compiles without diagnostics, but should produce two warnings because 5 is
not a power of two and so is not a valid alignment.
The attribute means that the call to alloc(10, 5) returns memory aligned to 5,
which seems unlikely. I think the attribute should imply that the argument is a
valid alignment.
It's undefined to call that operator new with a value that is not a valid
alignment, so a warning is definitely warranted there.
