[clang] [clang] Fix -Wuninitialized for values passed by const pointers (PR #147221)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-analysis

Author: Igor Kudrin (igorkudrin)

<details>
<summary>Changes</summary>

This enables producing a "variable is uninitialized" warning when a value is passed to a pointer-to-const argument:

```
void foo(const int *);
void test() {
  int *v;
  foo(v);
}
```

Fixes #<!-- -->37460

---
Full diff: https://github.com/llvm/llvm-project/pull/147221.diff


2 Files Affected:

- (modified) clang/lib/Analysis/UninitializedValues.cpp (+5-8) 
- (modified) clang/test/SemaCXX/uninitialized.cpp (+6-2) 


``````````diff
diff --git a/clang/lib/Analysis/UninitializedValues.cpp b/clang/lib/Analysis/UninitializedValues.cpp
index b2a68b6c39a7e..540838f89f20c 100644
--- a/clang/lib/Analysis/UninitializedValues.cpp
+++ b/clang/lib/Analysis/UninitializedValues.cpp
@@ -438,13 +438,10 @@ void ClassifyRefs::VisitCallExpr(CallExpr *CE) {
     return;
   }
   bool isTrivialBody = hasTrivialBody(CE);
-  // If a value is passed by const pointer to a function,
-  // we should not assume that it is initialized by the call, and we
-  // conservatively do not assume that it is used.
-  // If a value is passed by const reference to a function,
-  // it should already be initialized.
-  for (CallExpr::arg_iterator I = CE->arg_begin(), E = CE->arg_end();
-       I != E; ++I) {
+  // A value passed by const pointer or reference to a function should already
+  // be initialized.
+  for (CallExpr::arg_iterator I = CE->arg_begin(), E = CE->arg_end(); I != E;
+       ++I) {
     if ((*I)->isGLValue()) {
       if ((*I)->getType().isConstQualified())
         classify((*I), isTrivialBody ? Ignore : ConstRefUse);
@@ -453,7 +450,7 @@ void ClassifyRefs::VisitCallExpr(CallExpr *CE) {
       const auto *UO = dyn_cast<UnaryOperator>(Ex);
       if (UO && UO->getOpcode() == UO_AddrOf)
         Ex = UO->getSubExpr();
-      classify(Ex, Ignore);
+      classify(Ex, Use);
     }
   }
 }
diff --git a/clang/test/SemaCXX/uninitialized.cpp b/clang/test/SemaCXX/uninitialized.cpp
index c7b987e2172e6..4a944ba830bc3 100644
--- a/clang/test/SemaCXX/uninitialized.cpp
+++ b/clang/test/SemaCXX/uninitialized.cpp
@@ -162,12 +162,16 @@ void test_const_ptr() {
   int a;
   int b;  // expected-note {{initialize the variable 'b' to silence this warning}}
   foo(&a);
-  bar(&b);
-  b = a + b; // expected-warning {{variable 'b' is uninitialized when used here}}
+  bar(&b); // expected-warning {{variable 'b' is uninitialized when used here}}
+  b = a + b;
   int *ptr;  //expected-note {{initialize the variable 'ptr' to silence this warning}}
   const int *ptr2;
   foo(ptr); // expected-warning {{variable 'ptr' is uninitialized when used here}}
   foobar(&ptr2);
+  int *ptr3; // expected-note {{initialize the variable 'ptr3' to silence this warning}}
+  const int *ptr4; // expected-note {{initialize the variable 'ptr4' to silence this warning}}
+  bar(ptr3); // expected-warning {{variable 'ptr3' is uninitialized when used here}}
+  bar(ptr4); // expected-warning {{variable 'ptr4' is uninitialized when used here}}
 }
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/147221