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Fix UB in string.bench.cpp.

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The usage of aligned_storage failed to pass the alignment it wanted,
which caused it to have a larger size and alignment that the
std::string's it was intended to store.

This patch manually specifies the alignment, as well as cleaning up
type alias bugs.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@346779 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Fiselier
2018-11-13 19:16:19 +00:00
parent 10180dc28f
commit 6b8b8a113d
1 changed files with 6 additions and 6 deletions
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12
benchmarks/string.bench.cpp
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@@ -195,21 +195,21 @@ template <class Length>
struct StringMove { struct StringMove {
static void run(benchmark::State& state) { static void run(benchmark::State& state) {
// Keep two object locations and move construct back and forth. // Keep two object locations and move construct back and forth.
std::aligned_storage<sizeof(std::string)>::type Storage[2]; std::aligned_storage<sizeof(std::string), alignof(std::string)>::type Storage[2];
using S = std::string; using S = std::string;
S* Data = reinterpret_cast<S*>(Storage);
size_t I = 0; size_t I = 0;
new (static_cast<void*>(Data)) std::string(makeString(Length())); S *newS = new (static_cast<void*>(Storage)) std::string(makeString(Length()));
for (auto _ : state) { for (auto _ : state) {
// Switch locations. // Switch locations.
I ^= 1; I ^= 1;
benchmark::DoNotOptimize(Storage); benchmark::DoNotOptimize(Storage);
// Move construct into the new location, // Move construct into the new location,
new (static_cast<void*>(Storage + I)) S(std::move(Data[I ^ 1])); S *tmpS = new (static_cast<void*>(Storage + I)) S(std::move(*newS));
// then destroy the old one. // then destroy the old one.
Data[I ^ 1].~S(); newS->~S();
newS = tmpS;
} }
Data[I].~S(); newS->~S();
} }
static std::string name() { return "BM_StringMove" + Length::name(); } static std::string name() { return "BM_StringMove" + Length::name(); }