49 lines
2.1 KiB
Diff
49 lines
2.1 KiB
Diff
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From 7d1394bd639e3bcf68082ac3fc33eeed6a00d2e6 Mon Sep 17 00:00:00 2001
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From: Elly Fong-Jones <ellyjones@chromium.org>
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Date: Thu, 2 Mar 2023 00:15:11 +0000
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Subject: [PATCH] sql: relax constraints on VirtualCursor layout
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VirtualCursor::FromSqliteCursor required that VirtualCursor had a
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standard layout, but in fact VirtualCursor shouldn't have a standard
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layout, and the fact that it does with libc++ is a deviation from the
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C++ standard. This change:
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1. Relaxes the requirement that VirtualCursor has a standard layout, and
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2. Relaxes the requirement that the sqlite_cursor_ field has to be at
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offset 0
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by use of offsetof() and pointer subtraction. This change both improves
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standards compliance and makes this code build with libstdc++.
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Bug: 1380656
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Change-Id: I9c47abd9197b187da0360ca5619ccf7dadab4f33
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Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4292313
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Reviewed-by: Austin Sullivan <asully@chromium.org>
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Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
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Cr-Commit-Position: refs/heads/main@{#1111925}
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---
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sql/recover_module/cursor.h | 10 ++++------
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1 file changed, 4 insertions(+), 6 deletions(-)
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diff --git a/sql/recover_module/cursor.h b/sql/recover_module/cursor.h
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index 1970bdca8c6..4cb06557009 100644
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--- a/sql/recover_module/cursor.h
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+++ b/sql/recover_module/cursor.h
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@@ -63,12 +63,10 @@ class VirtualCursor {
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// |sqlite_cursor| must have been returned by VirtualTable::SqliteCursor().
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static inline VirtualCursor* FromSqliteCursor(
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sqlite3_vtab_cursor* sqlite_cursor) {
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- static_assert(std::is_standard_layout<VirtualCursor>::value,
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- "needed for the reinterpret_cast below");
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- static_assert(offsetof(VirtualCursor, sqlite_cursor_) == 0,
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- "sqlite_cursor_ must be the first member of the class");
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- VirtualCursor* result = reinterpret_cast<VirtualCursor*>(sqlite_cursor);
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- DCHECK_EQ(sqlite_cursor, &result->sqlite_cursor_);
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+ VirtualCursor* result = reinterpret_cast<VirtualCursor*>(
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+ (reinterpret_cast<char*>(sqlite_cursor) -
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+ offsetof(VirtualCursor, sqlite_cursor_)));
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+ CHECK_EQ(sqlite_cursor, &result->sqlite_cursor_);
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return result;
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}
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