On 11/04/2015 12:11 PM, Martin Sebor wrote:
On 11/02/2015 07:40 PM, Jason Merrill wrote:
On 10/26/2015 09:48 PM, Martin Sebor wrote:
+ while (TREE_CODE (oper) == NOP_EXPR)
+ oper = TREE_OPERAND (oper, 0);
This is STRIP_NOPS.
+ to placement new is not checked since it's unknownwhat it might
Missing space.
+ else if (TREE_CODE (oper) == ADDR_EXPR) {
The brace should go on its own line.
+ /* A possibly optimistic estimate Number of bytes available
Maybe "of the number"?
Thanks for the review. I've fixed the issues above in the latest
patch (attached).
+ /* When the referenced object is a member of a union, use the
size
+ of the entire union as the size of the buffer. */
Why? If we're accessing one union member, we should limit the allowed
space to the size of that member.
I followed the more permissive approach taken by _FORTIFY_SOURCE
where the size of the whole object is used (on the assumption that
we will eventually want to adopt the same mechanism here). For
instance, given:
union U { char c; int i; } u;
GCC doesn't diagnose:
memset (&u.c, 0, sizeof u);
so I didn't expect we'd want the following diagnosed either:
new (&u.c) U ();
But if you think it's preferable to use the size of the member
for this iteration of the placement new warning I can change it.
Can you confirm?
There was a lot of discussion of C++ aliasing rules at the recent
meeting; we really seem to be moving in the direction of being stricter
about which union member is active. So I think we do want to diagnose
the new-expression above; the user should write new (&u) if that's what
they mean.
+ if (bytes_avail <= abs (adjust))
+ bytes_avail = 0;
+ else if (0 <= adjust)
+ bytes_avail -= adjust;
+ else
+ bytes_avail += adjust;
If adjust is negative, I would think that we would have returned already
because we were dealing with an offset from a pointer of unknown value.
Adjust is negative when the offset to a buffer of known size is
negative. For example:
char buf [sizeof (int)];
new (&buf [1] - 1) int;
OK, so because we're looking at the expression from the outside in, we
first see the subtraction and adjust becomes -1, then we see the
array_ref and adjust returns to 0. We still don't have a negative
adjust by the time we get to the quoted if/else.
It also seems that you're being careful to avoid bytes_avail going
negative, so I wonder why you have it signed and bytes_need unsigned.
+ warning_at (EXPR_LOC_OR_LOC (orig_oper, input_location),
Let's remember this location early on so you don't need orig_oper.
Done.
Martin
