From: Alex Lorenz <arphaman@gmail.com>
Date: Thu, 27 Oct 2016 13:30:51 +0000 (+0000)
Subject: [Sema] -Wunused-variable warning for array variables should behave
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=39bf9749a5f06fd161878212c9718b6bf7190165;p=clang

[Sema] -Wunused-variable warning for array variables should behave
similarly to scalar variables.

This commit makes the -Wunused-variable warning behaviour more consistent:
Now clang won't warn for array variables where it doesn't warn for scalar
variables.

rdar://24158862

Differential Revision: https://reviews.llvm.org/D25937


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@285289 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index c8973ae100..a94ed53294 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1522,7 +1522,7 @@ static bool ShouldDiagnoseUnusedDecl(const NamedDecl *D) {
   if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
 
     // White-list anything with an __attribute__((unused)) type.
-    QualType Ty = VD->getType();
+    const auto *Ty = VD->getType().getTypePtr();
 
     // Only look at the outermost level of typedef.
     if (const TypedefType *TT = Ty->getAs<TypedefType>()) {
@@ -1535,6 +1535,10 @@ static bool ShouldDiagnoseUnusedDecl(const NamedDecl *D) {
     if (Ty->isIncompleteType() || Ty->isDependentType())
       return false;
 
+    // Look at the element type to ensure that the warning behaviour is
+    // consistent for both scalars and arrays.
+    Ty = Ty->getBaseElementTypeUnsafe();
+
     if (const TagType *TT = Ty->getAs<TagType>()) {
       const TagDecl *Tag = TT->getDecl();
       if (Tag->hasAttr<UnusedAttr>())
diff --git a/test/SemaCXX/warn-everthing.cpp b/test/SemaCXX/warn-everthing.cpp
index ad3dd8a24d..ff66c78cdf 100644
--- a/test/SemaCXX/warn-everthing.cpp
+++ b/test/SemaCXX/warn-everthing.cpp
@@ -9,5 +9,5 @@ public:
 };
 
 void testPR12271() { // expected-warning {{no previous prototype for function 'testPR12271'}}
-  PR12271 a[1][1]; // expected-warning {{unused variable 'a'}}
+  PR12271 a[1][1];
 }
diff --git a/test/SemaCXX/warn-unused-variables.cpp b/test/SemaCXX/warn-unused-variables.cpp
index 8dcbe7271d..e40cf1a2c9 100644
--- a/test/SemaCXX/warn-unused-variables.cpp
+++ b/test/SemaCXX/warn-unused-variables.cpp
@@ -150,3 +150,54 @@ namespace ctor_with_cleanups {
 }
 
 #include "Inputs/warn-unused-variables.h"
+
+namespace arrayRecords {
+
+int total = 0;
+
+class Adder {
+public:
+  Adder(int x); // out of line below
+  ~Adder() {}
+};
+
+Adder::Adder(int x) {
+  total += x;
+}
+
+struct Foo {
+  int x;
+  Foo(int x) : x(x) {}
+};
+
+struct S1 {
+  S1();
+};
+
+void foo(int size) {
+  S1 y; // no warning
+  S1 yarray[2]; // no warning
+  S1 dynArray[size]; // no warning
+  S1 nestedArray[1][2][3]; // no warning
+
+  Adder scalerInFuncScope = 134; // no warning
+  Adder arrayInFuncScope[] = { 135, 136 };  // no warning
+  Adder nestedArrayInFuncScope[2][2] = { {1,2}, {3,4} }; // no warning
+
+  Foo fooScalar = 1; // expected-warning {{unused variable 'fooScalar'}}
+  Foo fooArray[] = {1,2}; // expected-warning {{unused variable 'fooArray'}}
+  Foo fooNested[2][2] = { {1,2}, {3,4} }; // expected-warning {{unused variable 'fooNested'}}
+}
+
+template<int N>
+void bar() {
+  Adder scaler = 123; // no warning
+  Adder array[N] = {1,2}; // no warning
+}
+
+void test() {
+  foo(10);
+  bar<2>();
+}
+
+}