[clang] [Clang] FunctionEffects: properly extract the type of a bound member member function from a CallExpr. (PR #166101)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Doug Wyatt (dougsonos)

<details>
<summary>Changes</summary>

There's a bug illustrated by this example:

```
template &lt;typename T&gt;
struct Holder {
        T value;
        
        T&amp; operator*() { return value; }
};

struct X {
        using Dispatch = float (X::*)() [[clang::nonblocking]];
    
        void fails(Holder&lt;Dispatch&gt;&amp; holder) [[clang::nonblocking]]
        {
                (this-&gt;*(*holder))();   &lt;&lt;&lt; the expression is 
incorrectly determined not to be nonblocking
        }

        void succeeds(Holder&lt;Dispatch&gt;&amp; holder) [[clang::nonblocking]]
        {
                auto func = *holder;
                (this-&gt;*func)();
        }
};
```

In both cases we have a `CXXMemberCallExpr`.  In `succeeds`, the expression 
refers to a `Decl` (`func`) and gets a useful PTMF type.  In `fails`, the 
expression does not refer to a `Decl` and its type is special, printed as 
`bound member function`.  `Expr` provides a method for extracting the true type 
so we can use that in this situation.

---
Full diff: https://github.com/llvm/llvm-project/pull/166101.diff


2 Files Affected:

- (modified) clang/lib/Sema/SemaFunctionEffects.cpp (+11-2) 
- (modified) clang/test/Sema/attr-nonblocking-constraints.cpp (+14-1) 


``````````diff
diff --git a/clang/lib/Sema/SemaFunctionEffects.cpp 
b/clang/lib/Sema/SemaFunctionEffects.cpp
index 8590ee831084f..6d7bcbf53fe0f 100644
--- a/clang/lib/Sema/SemaFunctionEffects.cpp
+++ b/clang/lib/Sema/SemaFunctionEffects.cpp
@@ -1208,8 +1208,17 @@ class Analyzer {
         return true;
       }
 
-      // No Decl, just an Expr. Just check based on its type.
-      checkIndirectCall(Call, CalleeExpr->getType());
+      // No Decl, just an Expr. Just check based on its type. Bound member
+      // functions are a special expression type and need to be specially
+      // unpacked.
+      QualType CalleeExprQT = CalleeExpr->getType();
+      if (CalleeExpr->isBoundMemberFunction(Outer.S.getASTContext())) {
+        QualType QT = Expr::findBoundMemberType(CalleeExpr);
+        if (!QT.isNull()) {
+          CalleeExprQT = QT;
+        }
+      }
+      checkIndirectCall(Call, CalleeExprQT);
 
       return true;
     }
diff --git a/clang/test/Sema/attr-nonblocking-constraints.cpp 
b/clang/test/Sema/attr-nonblocking-constraints.cpp
index b26a945843696..22f7e23f81cf9 100644
--- a/clang/test/Sema/attr-nonblocking-constraints.cpp
+++ b/clang/test/Sema/attr-nonblocking-constraints.cpp
@@ -236,9 +236,22 @@ void nb13() [[clang::nonblocking]] { nb12(); }
 struct PTMFTester {
        typedef void (PTMFTester::*ConvertFunction)() [[clang::nonblocking]];
 
+       ConvertFunction mConvertFunc;
+
        void convert() [[clang::nonblocking]];
 
-       ConvertFunction mConvertFunc;
+       template <typename T>
+       struct Holder {
+               T value;
+               
+               T& operator*() { return value; }
+       };
+
+
+       void ptmfInExpr(Holder<ConvertFunction>& holder) [[clang::nonblocking]]
+       {
+               (this->*(*holder))(); // This should not generate a warning.
+       }
 };
 
 void PTMFTester::convert() [[clang::nonblocking]]

``````````

</details>


https://github.com/llvm/llvm-project/pull/166101
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