[clang][ast]: Add DynamicAllocLValue and TypeInfoLValue support to APValue::dump(). #135178

YLChenZ · 2025-04-10T13:38:47Z

Closes #134996.
The crash about TypeInfoLValue is https://godbolt.org/z/73WY31s55.
After the patch:

//test.cpp
#include <typeinfo>
constexpr const std::type_info* val = &typeid(int);

lambda@ubuntu22:~/test$ clang++ -std=c++20 -Xclang -ast-dump -fsyntax-only test.cpp
LValue Base=TypeInfoLValue typeid(int), Null=0, Offset=0, HasPath=1, PathLength=0, Path=()

//DAtest.cpp
constexpr int *m = new int(42);

lambda@ubuntu22:~/test$ clang++ -std=c++20 -Xclang -ast-dump -fsyntax-only DAtest.cpp
LValue Base=DynamicAllocLValue 'int', Null=0, Offset=0, HasPath=1, PathLength=0, Path=()

llvmbot · 2025-04-10T13:39:25Z

@llvm/pr-subscribers-clang

Author: None (YLChenZ)

Changes

Closes #134996.

The crash about TypeInfoLValue is https://godbolt.org/z/73WY31s55. The crash about DynamicAllocLValue I don't know how to reproduce it yet.

Before the patch:

......
`-VarDecl 0x118857f0 &lt;&lt;source&gt;:3:1, col:50&gt; col:33 val 'const std::type_info *const' constexpr cinit
  |-value: LValue Base=
clang++: /root/llvm-project/llvm/include/llvm/Support/Casting.h:566: decltype(auto) llvm::cast(const From&amp;) [with To = const clang::ValueDecl*; From = llvm::PointerUnion&lt;const clang::ValueDecl*, const clang::Expr*, clang::TypeInfoLValue, clang::DynamicAllocLValue&gt;]: Assertion `isa&lt;To&gt;(Val) &amp;&amp; "cast&lt;Ty&gt;() argument of incompatible type!"' failed.

After the patch:

......
`-VarDecl 0x55b81259b750 &lt;test.cpp:3:1, col:50&gt; col:33 val 'const std::type_info *const' constexpr cinit
  |-value: LValue Base=TypeInfoLValue, Null=0, Offset=0, HasPath=1, PathLength=0, Path=()
  `-UnaryOperator 0x55b81259b7f0 &lt;col:39, col:50&gt; 'const std::type_info *' prefix '&amp;' cannot overflow
    `-CXXTypeidExpr 0x55b81259b7d0 &lt;col:40, col:50&gt; 'const std::type_info' lvalue

Full diff: https://github.com/llvm/llvm-project/pull/135178.diff

2 Files Affected:

(modified) clang/lib/AST/TextNodeDumper.cpp (+4)
(modified) clang/test/AST/ast-dump-APValue-lvalue.cpp (+10-2)

diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
index be8d609974d81..0849e5642f006 100644
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -738,6 +738,10 @@ void TextNodeDumper::Visit(const APValue &Value, QualType Ty) {
     else if (const auto *BE = B.dyn_cast<const Expr *>()) {
       OS << BE->getStmtClassName() << ' ';
       dumpPointer(BE);
+    } else if (B.is<TypeInfoLValue>()) {
+      OS << "TypeInfoLValue";
+    } else if (B.is<DynamicAllocLValue>()) {
+      OS << "DynamicAllocLValue";
     } else {
       const auto *VDB = B.get<const ValueDecl *>();
       OS << VDB->getDeclKindName() << "Decl";
diff --git a/clang/test/AST/ast-dump-APValue-lvalue.cpp b/clang/test/AST/ast-dump-APValue-lvalue.cpp
index 224caddb3eabe..7e520254da41a 100644
--- a/clang/test/AST/ast-dump-APValue-lvalue.cpp
+++ b/clang/test/AST/ast-dump-APValue-lvalue.cpp
@@ -23,6 +23,10 @@ struct F {
 };
 F f;
 
+namespace std {
+  class type_info;
+}
+
 void Test(int (&arr)[10]) {
   constexpr int *pi = &i;
   // CHECK:  | `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}} pi 'int *const' constexpr cinit
@@ -45,6 +49,10 @@ void Test(int (&arr)[10]) {
   // CHECK-NEXT:  |   |-value: LValue Base=VarDecl {{.*}}, Null=0, Offset=2, HasPath=1, PathLength=2, Path=({{.*}}, 2)
 
   constexpr const int *n = nullptr;
-  // CHECK:    `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}} n 'const int *const' constexpr cinit
-  // CHECK-NEXT:      |-value: LValue Base=null, Null=1, Offset=0, HasPath=1, PathLength=0, Path=()
+  // CHECK:  | `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}} n 'const int *const' constexpr cinit
+  // CHECK-NEXT:  |   |-value: LValue Base=null, Null=1, Offset=0, HasPath=1, PathLength=0, Path=()
+
+  constexpr const std::type_info* pti = &typeid(int);
+  // CHECK:    `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}} pti 'const std::type_info *const' constexpr cinit
+  // CHECK-NEXT:      |-value: LValue Base=TypeInfoLValue, Null=0, Offset=0, HasPath=1, PathLength=0, Path=()
 }

tbaederr · 2025-04-11T07:03:52Z

clang/lib/AST/TextNodeDumper.cpp

+    } else if (B.is<TypeInfoLValue>()) {
+      OS << "TypeInfoLValue";
+    } else if (B.is<DynamicAllocLValue>()) {
+      OS << "DynamicAllocLValue";


Would be good to print more information about them.

tbaederr · 2025-04-11T07:21:42Z

I don't think we can test DynamicAllocLValue like this, since we can't save it in the APValue for an initialized global. You'll have to add a call to dump() e.g. like:

diff --git i/clang/lib/AST/ExprConstant.cpp w/clang/lib/AST/ExprConstant.cpp
index d1cc722fb794..df52ff82ea2a 100644
--- i/clang/lib/AST/ExprConstant.cpp
+++ w/clang/lib/AST/ExprConstant.cpp
@@ -17087,6 +17087,8 @@ bool Expr::EvaluateAsInitializer(APValue &Value, const ASTContext &Ctx,
         return false;
     }

+    Value.dump();
+
     // At this point, any lifetime-extended temporaries are completely
     // initialized.
     Info.performLifetimeExtension();

then you can compile

constexpr int *m = new int(12);

to reproduce it.

YLChenZ · 2025-04-11T14:21:36Z

I don't think we can test DynamicAllocLValue like this, since we can't save it in the APValue for an initialized global. You'll have to add a call to dump() e.g. like:

diff --git i/clang/lib/AST/ExprConstant.cpp w/clang/lib/AST/ExprConstant.cpp
index d1cc722fb794..df52ff82ea2a 100644
--- i/clang/lib/AST/ExprConstant.cpp
+++ w/clang/lib/AST/ExprConstant.cpp
@@ -17087,6 +17087,8 @@ bool Expr::EvaluateAsInitializer(APValue &Value, const ASTContext &Ctx,
         return false;
     }

+    Value.dump();
+
     // At this point, any lifetime-extended temporaries are completely
     // initialized.
     Info.performLifetimeExtension();

then you can compile

constexpr int *m = new int(12);

to reproduce it.

Okay, I got it. Already reproduced the crash.

lambda@ubuntu22:~/test$ clang++ -std=c++20 -Xclang -ast-dump -fsyntax-only DAtest.cpp
LValue Base=DynamicAllocLValue, Null=0, Offset=0, HasPath=1, PathLength=0, Path=()
DAtest.cpp:1:16: error: constexpr variable 'm' must be initialized by a constant expression
    1 | constexpr int *m = new int(42);
      |                ^   ~~~~~~~~~~~
DAtest.cpp:1:16: note: pointer to heap-allocated object is not a constant expression
DAtest.cpp:1:20: note: heap allocation performed here
    1 | constexpr int *m = new int(42);
      |                    ^
LValue Base=DynamicAllocLValue, Null=0, Offset=0, HasPath=1, PathLength=0, Path=()

YLChenZ · 2025-04-11T15:16:53Z

Would be good to print more information about them.

@tbaederr It seems to only dump their type, like this:

case APValue::LValue: {
    (void)Context;
    OS << "LValue Base=";
    APValue::LValueBase B = Value.getLValueBase();
    ...
    } else if (B.is<TypeInfoLValue>()) {
      OS << "TypeInfoLValue";
      const auto BTI = B.get<TypeInfoLValue>();
      BTI.print(OS, PrintPolicy);
    } else if (B.is<DynamicAllocLValue>()) {
      OS << "DynamicAllocLValue";
      auto BDA = B.getDynamicAllocType();
      dumpType(BDA);
    }

//test.cpp
#include <typeinfo>
constexpr const std::type_info* val = &typeid(int);

lambda@ubuntu22:~/test$ clang++ -std=c++20 -Xclang -ast-dump -fsyntax-only test.cpp
LValue Base=TypeInfoLValue typeid(int), Null=0, Offset=0, HasPath=1, PathLength=0, Path=()

//DAtest.cpp
constexpr int *m = new int(42);

lambda@ubuntu22:~/test$ clang++ -std=c++20 -Xclang -ast-dump -fsyntax-only DAtest.cpp
LValue Base=DynamicAllocLValue 'int', Null=0, Offset=0, HasPath=1, PathLength=0, Path=()

…Value::dump()

github-actions · 2025-04-14T02:53:20Z

✅ With the latest revision this PR passed the C/C++ code formatter.

clang/lib/AST/TextNodeDumper.cpp

tbaederr · 2025-04-15T11:59:26Z

Can you merge this or do you need to someone else to do it for you?

YLChenZ · 2025-04-15T12:13:17Z

@tbaederr I don't have access to merge pr. It should require some help to merge.

…Value::dump(). (llvm#135178) Closes llvm#134996. The crash about `TypeInfoLValue` is https://godbolt.org/z/73WY31s55. After the patch: ```cpp //test.cpp #include <typeinfo> constexpr const std::type_info* val = &typeid(int); ``` ``` lambda@ubuntu22:~/test$ clang++ -std=c++20 -Xclang -ast-dump -fsyntax-only test.cpp LValue Base=TypeInfoLValue typeid(int), Null=0, Offset=0, HasPath=1, PathLength=0, Path=() ``` ```cpp //DAtest.cpp constexpr int *m = new int(42); ``` ``` lambda@ubuntu22:~/test$ clang++ -std=c++20 -Xclang -ast-dump -fsyntax-only DAtest.cpp LValue Base=DynamicAllocLValue 'int', Null=0, Offset=0, HasPath=1, PathLength=0, Path=() ```

llvmbot added clang Clang issues not falling into any other category clang:frontend Language frontend issues, e.g. anything involving "Sema" labels Apr 10, 2025

YLChenZ mentioned this pull request Apr 10, 2025

Add DynamicAllocLValue and TypeInfoLValue support to APValue::dump() #134996

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tbaederr reviewed Apr 11, 2025

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YLChenZ added 2 commits April 14, 2025 10:43

[clang][ast]: Add DynamicAllocLValue and TypeInfoLValue support to AP…

1119ecf

…Value::dump()

print more information

23d850d

YLChenZ force-pushed the clang/AstLValue branch from 6368e47 to 23d850d Compare April 14, 2025 02:51

print more information

eec3fcd

YLChenZ requested a review from tbaederr April 14, 2025 03:42

tbaederr reviewed Apr 14, 2025

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clang/lib/AST/TextNodeDumper.cpp Outdated Show resolved Hide resolved

optimize code logic

64d2ea0

tbaederr approved these changes Apr 14, 2025

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Merge branch 'main' into clang/AstLValue

ef79156

tbaederr merged commit 9a6c001 into llvm:main Apr 15, 2025
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[clang][ast]: Add DynamicAllocLValue and TypeInfoLValue support to APValue::dump(). #135178

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