[PATCH] D143053: [C++20] [Modules] Pop Expression Evaluation Context when we skip its body during parsing

[Chuanqi Xu via Phabricator via cfe-commits]

ChuanqiXu created this revision.
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Close https://github.com/llvm/llvm-project/issues/60275

The root cause of issue 60275 is the imbalance of PushExpressionEvaluationContext() and PopExpressionEvaluationContext().

See https://github.com/llvm/llvm-project/blob/f1c4f927f7c15b5efdc3589c050fd0513bf6b303/clang/lib/Parse/Parser.cpp#L1396-L1437

We will  PushExpressionEvaluationContext() in ActOnStartOfFunctionDef() in line 1396 and we should pop it in ActOnFinishFunctionBody later. However if we skip the function body in line 1402, the expression evaluation context will not be popped. Then here is the issue report. I fix the issue by inserting codes to pop the expression evaluation context  explicitly if the function body is skipped. Maybe this looks like an ad-hoc fix. But if we want to fix this in a pretty way, we should refactor the current framework for pushing and popping expression evaluation contexts. Currently there are 23 PushExpressionEvaluationContext() callsities and 21 PopExpressionEvaluationContext() callsites in the code. And it seems not easy to balance them well and fast. So I suggest to land this fix first. At least it can prevent the crash.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D143053

Files:
  clang/lib/Parse/Parser.cpp
  clang/test/Modules/pr60275.cppm


Index: clang/test/Modules/pr60275.cppm
===================================================================
--- /dev/null
+++ clang/test/Modules/pr60275.cppm
@@ -0,0 +1,40 @@
+// Address: https://github.com/llvm/llvm-project/issues/60275
+//
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple -emit-module-interface %t/a.cppm -o %t/a.pcm
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/b.cpp -fmodule-file=%t/a.pcm -emit-llvm -o - | FileCheck %t/b.cpp
+//--- foo.h
+
+consteval void global() {}
+
+//--- a.cppm
+module;
+#include "foo.h"
+export module a;
+
+//--- b.cpp
+#include "foo.h"
+import a;
+
+consteval int b() {
+	return 0;
+}
+
+struct bb {
+	int m = b();
+};
+
+void bbb() {
+	bb x;
+}
+
+// CHECK: define{{.*}}_ZN2bbC2Ev({{.*}}[[THIS:%.+]])
+// CHECK-NEXT: entry:
+// CHECK-NEXT:   [[THIS_ADDR:%.*]] = alloca ptr
+// CHECK-NEXT:   store ptr [[THIS]], ptr [[THIS_ADDR]]
+// CHECK-NEXT:   [[THIS1:%.*]] = load ptr, ptr [[THIS_ADDR]]
+// CHECK-NEXT:   [[M_ADDR:%.*]] = getelementptr{{.*}}%struct.bb, ptr [[THIS1]], i32 0, i32 0
+// CHECK-NEXT:   store i32 0, ptr [[M_ADDR]]
Index: clang/lib/Parse/Parser.cpp
===================================================================
--- clang/lib/Parse/Parser.cpp
+++ clang/lib/Parse/Parser.cpp
@@ -14,6 +14,7 @@
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclTemplate.h"
+#include "clang/AST/ASTLambda.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Parse/ParseDiagnostic.h"
 #include "clang/Parse/RAIIObjectsForParser.h"
@@ -1404,6 +1405,17 @@
     if (BodyKind == Sema::FnBodyKind::Other)
       SkipFunctionBody();
 
+    // ExpressionEvaluationContext is pushed in ActOnStartOfFunctionDef
+    // and it would be popped in ActOnFinishFunctionBody.
+    // We pop it explcitly here since ActOnFinishFunctionBody won't get called.
+    //
+    // Do not call PopExpressionEvaluationContext() if it is a lambda because
+    // one is already popped when finishing the lambda in BuildLambdaExpr().
+    //
+    // FIXME: It looks not easy to balance PushExpressionEvaluationContext()
+    // and PopExpressionEvaluationContext().
+    if (!isLambdaCallOperator(dyn_cast_if_present<FunctionDecl>(Res)))
+      Actions.PopExpressionEvaluationContext();
     return Res;
   }
 


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