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From 5177b28400e03d8666dfb3e65c3016b5062ce0f7 Mon Sep 17 00:00:00 2001
From: Chih-Hung Hsieh <chh@google.com>
Date: Thu, 15 Nov 2018 16:07:02 -0800
Subject: [PATCH] Update asserts in mojo about int64_t's alignment
The purpose of these asserts is to check that the options structs are aligned
sufficiently that an int64_t (or similar) could be added to them. The asserts
were added in https://codereview.chromium.org/295383012
However, the alignment of int64_t on 32-bit x86 is actually 4 bytes, not 8. So
how did this ever work? Before Clang r345419, the alignof() operator (which is what
MOJO_ALIGNOF maps to) would return the *preferred alignment* of a type, not
the *ABI alignment*. That's not what the C and C++ standards specify, so the
bug was fixed and the asserts started firing. (See also
https://llvm.org/pr26547)
To fix the build, change the asserts to check that int64_t requires 8 bytes
alignment *or less*.
Bug: 900406
Bug: 119634736
Change-Id: Icf80cea80ac31082423faab8c192420d0b98d515
Reviewed-on: https://chromium-review.googlesource.com/c/1318971
Commit-Queue: Ken Rockot <rockot@google.com>
Reviewed-by: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#605699}
---
mojo/core/options_validation_unittest.cc | 2 +-
mojo/public/c/system/buffer.h | 2 +-
mojo/public/c/system/data_pipe.h | 2 +-
mojo/public/c/system/message_pipe.h | 2 +-
4 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/mojo/core/options_validation_unittest.cc b/mojo/core/options_validation_unittest.cc
index 52e0032..b4b02dc 100644
--- a/mojo/core/options_validation_unittest.cc
+++ b/mojo/core/options_validation_unittest.cc
@@ -18,7 +18,7 @@ namespace {
using TestOptionsFlags = uint32_t;
-static_assert(MOJO_ALIGNOF(int64_t) == 8, "int64_t has weird alignment");
+static_assert(MOJO_ALIGNOF(int64_t) <= 8, "int64_t has weird alignment");
struct MOJO_ALIGNAS(8) TestOptions {
uint32_t struct_size;
TestOptionsFlags flags;
diff --git a/mojo/public/c/system/buffer.h b/mojo/public/c/system/buffer.h
index 2cc5427..83b198b 100644
--- a/mojo/public/c/system/buffer.h
+++ b/mojo/public/c/system/buffer.h
@@ -30,7 +30,7 @@ struct MOJO_ALIGNAS(8) MojoCreateSharedBufferOptions {
// See |MojoCreateSharedBufferFlags|.
MojoCreateSharedBufferFlags flags;
};
-MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) == 8, "int64_t has weird alignment");
+MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) <= 8, "int64_t has weird alignment");
MOJO_STATIC_ASSERT(sizeof(MojoCreateSharedBufferOptions) == 8,
"MojoCreateSharedBufferOptions has wrong size");
diff --git a/mojo/public/c/system/data_pipe.h b/mojo/public/c/system/data_pipe.h
index 3702cdb..c72f553 100644
--- a/mojo/public/c/system/data_pipe.h
+++ b/mojo/public/c/system/data_pipe.h
@@ -40,7 +40,7 @@ struct MOJO_ALIGNAS(8) MojoCreateDataPipeOptions {
// system-dependent capacity of at least one element in size.
uint32_t capacity_num_bytes;
};
-MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) == 8, "int64_t has weird alignment");
+MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) <= 8, "int64_t has weird alignment");
MOJO_STATIC_ASSERT(sizeof(MojoCreateDataPipeOptions) == 16,
"MojoCreateDataPipeOptions has wrong size");
diff --git a/mojo/public/c/system/message_pipe.h b/mojo/public/c/system/message_pipe.h
index 9f222f9..0f642dd 100644
--- a/mojo/public/c/system/message_pipe.h
+++ b/mojo/public/c/system/message_pipe.h
@@ -35,7 +35,7 @@ struct MOJO_ALIGNAS(8) MojoCreateMessagePipeOptions {
// See |MojoCreateMessagePipeFlags|.
MojoCreateMessagePipeFlags flags;
};
-MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) == 8, "int64_t has weird alignment");
+MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) <= 8, "int64_t has weird alignment");
MOJO_STATIC_ASSERT(sizeof(MojoCreateMessagePipeOptions) == 8,
"MojoCreateMessagePipeOptions has wrong size");
--
2.20.0.rc0.387.gc7a69e6b6c-goog
|
