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Enforce trivially-copyable types on unaligned loads/stores/casts.

Browse Source 
These correctness checks were inspired by Chromium's bit_cast:
https://chromium.googlesource.com/chromium/src/base/+/refs/heads/master/bit_cast.h

This also closes out a long-standing TODO in the code.

Change-Id: Iaf570fc564955ba90115a52bcaa743a170bdbdc4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/305718
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
This commit is contained in:
John Stiles 2020-07-24 10:05:43 -04:00 committed by Skia Commit-Bot
parent 58adb34cda
commit 7109434de0
2 changed files with 8 additions and 4 deletions
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8
src/core/SkUtils.h
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@ -83,7 +83,8 @@ namespace SkHexadecimalDigits {
template <typename T, typename P> template <typename T, typename P>
static SK_ALWAYS_INLINE T sk_unaligned_load(const P* ptr) { static SK_ALWAYS_INLINE T sk_unaligned_load(const P* ptr) {
// TODO: static_assert desirable things about T here so as not to be totally abused. static_assert(std::is_trivially_copyable<T>::value);
static_assert(std::is_trivially_copyable<P>::value);
T val; T val;
memcpy(&val, ptr, sizeof(val)); memcpy(&val, ptr, sizeof(val));
return val; return val;
@ -91,13 +92,14 @@ static SK_ALWAYS_INLINE T sk_unaligned_load(const P* ptr) {
template <typename T, typename P> template <typename T, typename P>
static SK_ALWAYS_INLINE void sk_unaligned_store(P* ptr, T val) { static SK_ALWAYS_INLINE void sk_unaligned_store(P* ptr, T val) {
// TODO: ditto static_assert(std::is_trivially_copyable<T>::value);
static_assert(std::is_trivially_copyable<P>::value);
memcpy(ptr, &val, sizeof(val)); memcpy(ptr, &val, sizeof(val));
} }
template <typename Dst, typename Src> template <typename Dst, typename Src>
static SK_ALWAYS_INLINE Dst sk_bit_cast(const Src& src) { static SK_ALWAYS_INLINE Dst sk_bit_cast(const Src& src) {
static_assert(sizeof(Dst) == sizeof(Src), ""); static_assert(sizeof(Dst) == sizeof(Src));
return sk_unaligned_load<Dst>(&src); return sk_unaligned_load<Dst>(&src);
} }

4
src/opts/SkRasterPipeline_opts.h
View File

@ -22,7 +22,9 @@
template <typename Dst, typename Src> template <typename Dst, typename Src>
SI Dst widen_cast(const Src& src) { SI Dst widen_cast(const Src& src) {
static_assert(sizeof(Dst) > sizeof(Src), ""); static_assert(sizeof(Dst) > sizeof(Src));
static_assert(std::is_trivially_copyable<Dst>::value);
static_assert(std::is_trivially_copyable<Src>::value);
Dst dst; Dst dst;
memcpy(&dst, &src, sizeof(Src)); memcpy(&dst, &src, sizeof(Src));
return dst; return dst;