From e4b2f3054a77ec28d501e269affbac6cfdfda35c Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Tue, 31 Aug 2021 07:04:31 -0400
Subject: [PATCH] [WebAssembly][libObject] Avoid re-use of Section object
 during parsing

The re-use of this struct across iterations of the loop was causing
fields (specifically Name) to be incorrectly shared between multiple
sections.

Differential Revision: https://reviews.llvm.org/D108984
---
 llvm/lib/Object/WasmObjectFile.cpp            |  2 +-
 .../llvm-objcopy/wasm/basic-only-section.test | 25 +++++++++----------
 2 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index a08c648358c0..9a4e246f765a 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -286,9 +286,9 @@ WasmObjectFile::WasmObjectFile(MemoryBufferRef Buffer, Error &Err)
     return;
   }
 
-  WasmSection Sec;
   WasmSectionOrderChecker Checker;
   while (Ctx.Ptr < Ctx.End) {
+    WasmSection Sec;
     if ((Err = readSection(Sec, Ctx, Checker)))
       return;
     if ((Err = parseSection(Sec)))
diff --git a/llvm/test/tools/llvm-objcopy/wasm/basic-only-section.test b/llvm/test/tools/llvm-objcopy/wasm/basic-only-section.test
index f4b7d91a1236..fe47d5c02773 100644
--- a/llvm/test/tools/llvm-objcopy/wasm/basic-only-section.test
+++ b/llvm/test/tools/llvm-objcopy/wasm/basic-only-section.test
@@ -1,32 +1,36 @@
 ## Test --only-section.
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-objcopy --only-section=producers %t %t2
+# RUN: llvm-objcopy --only-section=foo %t %t2
 # RUN: obj2yaml %t2 | FileCheck --implicit-check-not TYPE --implicit-check-not linking %s
 
 ## Test that it's the same with only-section + keep-section (for the same section).
-# RUN: llvm-objcopy --only-section=producers --keep-section=producers %t %t2
+# RUN: llvm-objcopy --only-section=foo --keep-section=foo %t %t2
 # RUN: obj2yaml %t2 | FileCheck --implicit-check-not TYPE --implicit-check-not linking %s
 
 ## Also test that only-section overrides remove-section.
-# RUN: llvm-objcopy --only-section=producers --remove-section=producers %t %t2
+# RUN: llvm-objcopy --only-section=foo --remove-section=foo %t %t2
 # RUN: obj2yaml %t2 | FileCheck --implicit-check-not linking %s
 
-## This file has both known and custom sections. Check that only the producers section is left.
+## This file has both known and custom sections. Check that only the foo section is left.
 # CHECK:      Sections:
 # CHECK-NEXT:   - Type: CUSTOM
-# CHECK-NEXT:     Name: producers
-# CHECK-NEXT:     Tools:
+# CHECK-NEXT:     Name: foo
+# CHECK-NEXT:     Payload: DEADBEEF
+# CHECK-NEXT: ...
 
 ## Test that only-section + keep-section keeps both sections.
-# RUN: llvm-objcopy --only-section=producers --keep-section=linking %t %t2
+# RUN: llvm-objcopy --only-section=foo --keep-section=linking %t %t2
 # RUN: obj2yaml %t2 | FileCheck --implicit-check-not=TYPE --check-prefix=KEEP %s
+# KEEP: Name: foo
 # KEEP: Name: linking
-# KEEP: Name: producers
 
 --- !WASM
 FileHeader:
   Version: 0x00000001
 Sections:
+  - Type: CUSTOM
+    Name: foo
+    Payload: DEADBEEF
   - Type: TYPE
     Signatures:
       - Index: 0
@@ -37,8 +41,3 @@ Sections:
   - Type: CUSTOM
     Name: linking
     Version: 2
-  - Type: CUSTOM
-    Name: producers
-    Tools:
-      - Name:   clang
-        Version: 9.0.0