103 lines
4.3 KiB
Diff
103 lines
4.3 KiB
Diff
From 6b633c4b14850df376d5cec571699018772f358e Mon Sep 17 00:00:00 2001
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From: Tomas Popela <tomas.popela@gmail.com>
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Date: Tue, 17 Sep 2019 19:48:48 +0000
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Subject: [PATCH] GCC: Can't use alignas() together with __attribute__()
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It's because GCC has problems when mixing the alignas() together with
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__attribute__() (that is used to export the symbols). The best
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solution is to use ALIGNAS() macro from //base/compiler_specific.h
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together with alignof() to have the equal functionality that compiles on
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GCC as well as on clang.
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Bug: 819294
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Change-Id: Ieb169592a2965f17a18bfc88d28418eb723a4e5a
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Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1806735
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Auto-Submit: Tom Popela <tomas.popela@gmail.com>
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Commit-Queue: Alex Clarke <alexclarke@chromium.org>
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Reviewed-by: Alex Clarke <alexclarke@chromium.org>
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Cr-Commit-Position: refs/heads/master@{#697330}
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---
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diff --git a/base/task/promise/dependent_list.h b/base/task/promise/dependent_list.h
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index 020bdbfc..3245c1c 100644
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--- a/base/task/promise/dependent_list.h
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+++ b/base/task/promise/dependent_list.h
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@@ -59,7 +59,7 @@
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// Align Node on an 8-byte boundary to ensure the first 3 bits are 0 and can
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// be used to store additional state (see static_asserts below).
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- class BASE_EXPORT alignas(8) Node {
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+ class BASE_EXPORT ALIGNAS(8) Node {
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public:
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Node();
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explicit Node(Node&& other) noexcept;
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Re-use chromium alignas workaround in protobuf.
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---
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diff --git a/third_party/protobuf/src/google/protobuf/port_def.inc b/third_party/protobuf/src/google/protobuf/port_def.inc
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index f1bd85d..9c204a1 100644
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--- a/third_party/protobuf/src/google/protobuf/port_def.inc
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+++ b/third_party/protobuf/src/google/protobuf/port_def.inc
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@@ -528,6 +528,35 @@ PROTOBUF_EXPORT_TEMPLATE_TEST(DEFAULT, __declspec(dllimport));
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#undef IN
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#endif // _MSC_VER
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+// Specify memory alignment for structs, classes, etc.
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+// Use like:
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+// class PROTOBUF_ALIGNAS(16) MyClass { ... }
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+// PROTOBUF_ALIGNAS(16) int array[4];
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+//
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+// In most places you can use the C++11 keyword "alignas", which is preferred.
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+//
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+// But compilers have trouble mixing __attribute__((...)) syntax with
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+// alignas(...) syntax.
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+//
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+// Doesn't work in clang or gcc:
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+// struct alignas(16) __attribute__((packed)) S { char c; };
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+// Works in clang but not gcc:
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+// struct __attribute__((packed)) alignas(16) S2 { char c; };
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+// Works in clang and gcc:
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+// struct alignas(16) S3 { char c; } __attribute__((packed));
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+//
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+// There are also some attributes that must be specified *before* a class
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+// definition: visibility (used for exporting functions/classes) is one of
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+// these attributes. This means that it is not possible to use alignas() with a
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+// class that is marked as exported.
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+#if defined(_MSC_VER)
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+#define PROTOBUF_ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
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+#elif defined(__GNUC__)
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+#define PROTOBUF_ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
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+#else
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+#define PROTOBUF_ALIGNAS(byte_alignment) alignas(byte_alignment)
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+#endif
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+
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#if defined(__clang__)
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#pragma clang diagnostic push
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// TODO(gerbens) ideally we cleanup the code. But a cursory try shows many
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diff --git a/third_party/protobuf/src/google/protobuf/arena.h b/third_party/protobuf/src/google/protobuf/arena.h
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index dedc221..a8515ce 100644
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--- a/third_party/protobuf/src/google/protobuf/arena.h
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+++ b/third_party/protobuf/src/google/protobuf/arena.h
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@@ -245,7 +245,7 @@ struct ArenaOptions {
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// well as protobuf container types like RepeatedPtrField and Map. The protocol
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// is internal to protobuf and is not guaranteed to be stable. Non-proto types
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// should not rely on this protocol.
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-class PROTOBUF_EXPORT alignas(8) Arena final {
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+class PROTOBUF_EXPORT PROTOBUF_ALIGNAS(8) Arena final {
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public:
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// Arena constructor taking custom options. See ArenaOptions below for
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// descriptions of the options available.
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diff --git a/third_party/protobuf/src/google/protobuf/port_undef.inc b/third_party/protobuf/src/google/protobuf/port_undef.inc
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index b7e67fe..ba1fffc 100644
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--- a/third_party/protobuf/src/google/protobuf/port_undef.inc
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+++ b/third_party/protobuf/src/google/protobuf/port_undef.inc
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@@ -80,6 +80,7 @@
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#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA__declspec
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#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllexport
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#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllimport
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+#undef PROTOBUF_ALIGNAS
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