On Tue, Jan 21, 2025 at 11:06:35AM -0500, Jason Merrill wrote:
> > --- gcc/c-family/c-common.cc.jj 2025-01-20 18:00:35.667875671 +0100
> > +++ gcc/c-family/c-common.cc 2025-01-21 09:29:23.955582581 +0100
> > @@ -9010,33 +9010,46 @@ make_tree_vector_from_list (tree list)
> > return ret;
> > }
> > -/* Get a new tree vector of the values of a CONSTRUCTOR. */
> > +/* Append to a tree vector the values of a CONSTRUCTOR.
> > + nelts should be at least CONSTRUCTOR_NELTS (ctor) and v
> > + should be initialized with make_tree_vector (); followed by
> > + vec_safe_reserve (v, nelts); or equivalently vec_alloc (v, nelts);
> > + optionally followed by pushes of other elements (up to
> > + nelts - CONSTRUCTOR_NELTS (ctor)). */
>
> How about using v->allocated () instead of passing in nelts?
That is not necessarily the same.
Both vec_safe_reserve (v, nelts) and vec_alloc (v, nelts); actually
use exact=false, so they can allocate something larger (doesn't hurt
e.g. if RAW_DATA_CST is small enough and fits), but if it used v->allocated
(), it could overallocate from the overallocated size.
So, e.g. even if nelts + RAW_DATA_LENGTH (x) - 1 <= v->allocated () - v->length
()
and thus we could just use a vector without reallocating,
v->allocated () + RAW_DATA_LENGTH (x) - 1 could be too much.
Jakub
