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| author | Jonathan Wakely <jwakely@redhat.com> | 2019-04-11 20:58:14 +0100 |
|---|---|---|
| committer | Jonathan Wakely <redi@gcc.gnu.org> | 2019-04-11 20:58:14 +0100 |
| commit | 2c390a483bcbd114325bb27e47dcdebb49798fdf (patch) | |
| tree | c6c0720f0c7f85c677449ef59e07871973d6af2e | |
| parent | 76d7e3f0246ed279d613e8c526168f48fe240afb (diff) | |
| download | gcc-2c390a483bcbd114325bb27e47dcdebb49798fdf.zip gcc-2c390a483bcbd114325bb27e47dcdebb49798fdf.tar.gz gcc-2c390a483bcbd114325bb27e47dcdebb49798fdf.tar.bz2 | |
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.
From-SVN: r270291
| -rw-r--r-- | libstdc++-v3/ChangeLog | 8 | ||||
| -rw-r--r-- | libstdc++-v3/src/c++17/memory_resource.cc | 17 |
2 files changed, 22 insertions, 3 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index 6148f5ce..d49ce7c 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,11 @@ +2019-04-11 Jonathan Wakely <jwakely@redhat.com> + + 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. + 2019-04-10 Jonathan Wakely <jwakely@redhat.com> * doc/xml/faq.xml: Add information about emergency EH pool. diff --git a/libstdc++-v3/src/c++17/memory_resource.cc b/libstdc++-v3/src/c++17/memory_resource.cc index cd11bf5..b669801 100644 --- a/libstdc++-v3/src/c++17/memory_resource.cc +++ b/libstdc++-v3/src/c++17/memory_resource.cc @@ -182,7 +182,21 @@ namespace pmr _Chunk*& __head) { __size = std::__ceil2(__size + sizeof(_Chunk)); + + if constexpr (alignof(_Chunk) > 1) + { + // PR libstdc++/90046 + // For targets like epiphany-elf where alignof(_Chunk) != 1 + // ensure that the last sizeof(_Chunk) bytes in the buffer + // are suitably-aligned for a _Chunk. + // This should be unnecessary, because the caller already + // passes in max(__align, alignof(max_align_t)). + if (__align < alignof(_Chunk)) + __align = alignof(_Chunk); + } + void* __p = __r->allocate(__size, __align); + // Add a chunk defined by (__p, __size, __align) to linked list __head. void* const __back = (char*)__p + __size - sizeof(_Chunk); __head = ::new(__back) _Chunk(__size, __align, __head); @@ -231,9 +245,6 @@ namespace pmr void monotonic_buffer_resource::_M_new_buffer(size_t bytes, size_t alignment) { - // Need to check this somewhere, so put it here: - static_assert(alignof(monotonic_buffer_resource::_Chunk) == 1); - const size_t n = std::max(bytes, _M_next_bufsiz); const size_t m = std::max(alignment, alignof(std::max_align_t)); auto [p, size] = _Chunk::allocate(_M_upstream, n, m, _M_head); |