r270291 - in /trunk/libstdc++-v3: ChangeLog src...

redi@gcc.gnu.org redi@gcc.gnu.org
Thu Apr 11 19:58:00 GMT 2019

Author: redi
Date: Thu Apr 11 19:58:14 2019
New Revision: 270291

URL: https://gcc.gnu.org/viewcvs?rev=270291&root=gcc&view=rev
PR libstdc++/90046 fix build failure on epiphany-elf

The epiphany-elf target aligns structs to 8 bytes, which causes the
static_assert(alignof(_Chunk) == 1) to fail.

Instead of requiring _Chunks to be positionable at any alignment, ensure
new buffers are aligned to alignof(_Chunk). Because the buffer size is a
power of two, we know that both the buffer size and sizeof(_Chunk) are
multiples of alignof(_Chunk). So is p is aligned to alignof(_Chunk) then
so is (p + size - sizeof(_Chunk)). So just ensure the new buffer is
aligned to at least alignof(_Chunk), which should already be true
because the caller requests at least alignof(max_align_t).

	PR libstdc++/90046
	* src/c++17/memory_resource.cc
	(monotonic_buffer_resource::_Chunk::allocate): Increase alignment if
	needed to allow placing a _Chunk at the end of the buffer.
	(monotonic_buffer_resource::_M_new_buffer): Remove static_assert.


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