[PATCH] D79895: Fix warning about using uninitialized variable as function const reference parameter

[Zequan Wu via Phabricator via cfe-commits]

zequanwu created this revision.
zequanwu added reviewers: rsmith, rnk.
zequanwu added a project: clang.
Herald added a subscriber: cfe-commits.

bug filed here: https://bugs.llvm.org/show_bug.cgi?id=45624

Uninitialized variable as function const reference parameter should be use.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79895

Files:
  clang/lib/Analysis/UninitializedValues.cpp
  clang/test/SemaCXX/uninit-variables.cpp
  clang/test/SemaCXX/uninitialized.cpp


Index: clang/test/SemaCXX/uninitialized.cpp
===================================================================
--- clang/test/SemaCXX/uninitialized.cpp
+++ clang/test/SemaCXX/uninitialized.cpp
@@ -59,13 +59,13 @@
   int d = ({ d + d ;}); // expected-warning {{variable 'd' is uninitialized when used within its own initialization}}
   int e = static_cast<long>(e) + 1; // expected-warning {{variable 'e' is uninitialized when used within its own initialization}}
   int f = foo(f); // expected-warning {{variable 'f' is uninitialized when used within its own initialization}}
+  int j = far(j); // expected-warning {{variable 'j' is uninitialized when used within its own initialization}}
 
   // These don't warn as they don't require the value.
   int g = sizeof(g);
   void* ptr = &ptr;
   int h = bar(&h);
   int i = boo(i);
-  int j = far(j);
   int k = __alignof__(k);
 
   int l = k ? l : l;  // expected-warning {{variable 'l' is uninitialized when used within its own initialization}}
@@ -93,13 +93,13 @@
     int d = ({ d + d ;}); // expected-warning {{variable 'd' is uninitialized when used within its own initialization}}
     int e = static_cast<long>(e) + 1; // expected-warning {{variable 'e' is uninitialized when used within its own initialization}}
     int f = foo(f); // expected-warning {{variable 'f' is uninitialized when used within its own initialization}}
+    int j = far(j); // expected-warning {{variable 'j' is uninitialized when used within its own initialization}}
 
     // These don't warn as they don't require the value.
     int g = sizeof(g);
     void* ptr = &ptr;
     int h = bar(&h);
     int i = boo(i);
-    int j = far(j);
     int k = __alignof__(k);
 
     int l = k ? l : l;  // expected-warning {{variable 'l' is uninitialized when used within its own initialization}}
@@ -284,8 +284,8 @@
   A a34(std::move(a34));   // expected-warning {{variable 'a34' is uninitialized when used within its own initialization}}
   A a35 = std::move(x ? a34 : (37, a35));  // expected-warning {{variable 'a35' is uninitialized when used within its own initialization}}
 
-  A a36 = const_refA(a36);
-  A a37(const_refA(a37));
+  A a36 = const_refA(a36); // expected-warning {{variable 'a36' is uninitialized when used within its own initialization}}
+  A a37(const_refA(a37)); // expected-warning {{variable 'a37' is uninitialized when used within its own initialization}}
 
   A a38({a38});  // expected-warning {{variable 'a38' is uninitialized when used within its own initialization}}
   A a39 = {a39};  // expected-warning {{variable 'a39' is uninitialized when used within its own initialization}}
@@ -294,9 +294,9 @@
   A a41 = !a41;  // expected-warning {{variable 'a41' is uninitialized when used within its own initialization}}
   A a42 = !(a42);  // expected-warning {{variable 'a42' is uninitialized when used within its own initialization}}
   A a43 = a43 != a42;  // expected-warning {{variable 'a43' is uninitialized when used within its own initialization}}
-  A a44 = a43 != a44;  // expected-warning {{variable 'a44' is uninitialized when used within its own initialization}}
+  A a44 = a43 != a44;  // expected-warning 2{{variable 'a44' is uninitialized when used within its own initialization}}
   A a45 = a45 != a45;  // expected-warning 2{{variable 'a45' is uninitialized when used within its own initialization}}
-  A a46 = 0 != a46;  // expected-warning {{variable 'a46' is uninitialized when used within its own initialization}}
+  A a46 = 0 != a46;  // expected-warning 2{{variable 'a46' is uninitialized when used within its own initialization}}
 
   A a47(a47.set(a47.num));  // expected-warning 2{{variable 'a47' is uninitialized when used within its own initialization}}
   A a48(a47.set(a48.num));  // expected-warning {{variable 'a48' is uninitialized when used within its own initialization}}
Index: clang/test/SemaCXX/uninit-variables.cpp
===================================================================
--- clang/test/SemaCXX/uninit-variables.cpp
+++ clang/test/SemaCXX/uninit-variables.cpp
@@ -144,8 +144,8 @@
 void consume_const_ref(const int &n);
 int test_const_ref() {
   int n; // expected-note {{variable}}
-  consume_const_ref(n);
-  return n; // expected-warning {{uninitialized when used here}}
+  consume_const_ref(n); // expected-warning {{variable 'n' is uninitialized when used here}}
+  return n;
 }
 
 // Don't crash here.
Index: clang/lib/Analysis/UninitializedValues.cpp
===================================================================
--- clang/lib/Analysis/UninitializedValues.cpp
+++ clang/lib/Analysis/UninitializedValues.cpp
@@ -413,14 +413,16 @@
     return;
   }
 
-  // If a value is passed by const pointer or by const reference to a function,
+  // 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) {
     if ((*I)->isGLValue()) {
       if ((*I)->getType().isConstQualified())
-        classify((*I), Ignore);
+        classify((*I), Use);
     } else if (isPointerToConst((*I)->getType())) {
       const Expr *Ex = stripCasts(DC->getParentASTContext(), *I);
       const auto *UO = dyn_cast<UnaryOperator>(Ex);


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