[clang][bytecode] Fix a crash in __builtin_object_size()

[tbaederr]

The previous ByteOffset computation only makes sense if Ptr points into an array.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

Changes

The previous BytOffset computation only makes sense if Ptr points into an array.

---

Full diff: https://github.com/llvm/llvm-project/pull/160519.diff

2 Files Affected:

• (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+8-4)
• (modified) clang/test/AST/ByteCode/builtin-object-size.cpp (+2-1)

diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 5423d3ca73c81..a49992029c742 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -2449,10 +2449,14 @@ static bool interp__builtin_object_size(InterpState &S, CodePtr OpPC,
     if (Ptr.isBaseClass())
       ByteOffset = computePointerOffset(ASTCtx, Ptr.getBase()) -
                    computePointerOffset(ASTCtx, Ptr);
-    else
-      ByteOffset =
-          computePointerOffset(ASTCtx, Ptr) -
-          computePointerOffset(ASTCtx, Ptr.expand().atIndex(0).narrow());
+    else {
+      if (Ptr.inArray())
+        ByteOffset =
+            computePointerOffset(ASTCtx, Ptr) -
+            computePointerOffset(ASTCtx, Ptr.expand().atIndex(0).narrow());
+      else
+        ByteOffset = 0;
+    }
   } else
     ByteOffset = computePointerOffset(ASTCtx, Ptr);
 
diff --git a/clang/test/AST/ByteCode/builtin-object-size.cpp b/clang/test/AST/ByteCode/builtin-object-size.cpp
index 6f4ef54bcbafa..e4433ea700ccb 100644
--- a/clang/test/AST/ByteCode/builtin-object-size.cpp
+++ b/clang/test/AST/ByteCode/builtin-object-size.cpp
@@ -17,7 +17,8 @@ static_assert(__builtin_object_size(&arrf, 0) == (sizeof(float)*2), "");
 static_assert(__builtin_object_size(&arrf[1], 0) == sizeof(float), "");
 static_assert(__builtin_object_size(&arrf[2], 0) == 0, "");
 
-
+constexpr struct { int a; int b; } F{};
+static_assert(__builtin_object_size(&F.a, 3) == sizeof(int));
 
 struct S {
   int a;

[llvm-ci]

LLVM Buildbot has detected a new failure on builder llvm-clang-x86_64-darwin running on doug-worker-3 while building clang at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/23/builds/14472

Here is the relevant piece of the build log for the reference

Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang-Unit :: ./AllClangUnitTests/19/48' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/tools/clang/unittests/./AllClangUnitTests-Clang-Unit-3856-19-48.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=48 GTEST_SHARD_INDEX=19 /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/tools/clang/unittests/./AllClangUnitTests
--

Script:
--
/Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/tools/clang/unittests/./AllClangUnitTests --gtest_filter=DirectoryWatcherTest.DeleteWatchedDir
--
/Users/buildbot/buildbot-root/x86_64-darwin/llvm-project/clang/unittests/DirectoryWatcher/DirectoryWatcherTest.cpp:257: Failure
Value of: WaitForExpectedStateResult.wait_for(EventualResultTimeout) == std::future_status::ready
  Actual: false
Expected: true
The expected result state wasn't reached before the time-out.

/Users/buildbot/buildbot-root/x86_64-darwin/llvm-project/clang/unittests/DirectoryWatcher/DirectoryWatcherTest.cpp:260: Failure
Value of: TestConsumer.result().has_value()
  Actual: false
Expected: true


/Users/buildbot/buildbot-root/x86_64-darwin/llvm-project/clang/unittests/DirectoryWatcher/DirectoryWatcherTest.cpp:257
Value of: WaitForExpectedStateResult.wait_for(EventualResultTimeout) == std::future_status::ready
  Actual: false
Expected: true
The expected result state wasn't reached before the time-out.

/Users/buildbot/buildbot-root/x86_64-darwin/llvm-project/clang/unittests/DirectoryWatcher/DirectoryWatcherTest.cpp:260
Value of: TestConsumer.result().has_value()
  Actual: false
Expected: true



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