clang/test/SemaCXX/warn-pessmizing-move.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -Wpessimizing-move -std=c++11 -verify %s
   2 // RUN: %clang_cc1 -fsyntax-only -Wpessimizing-move -std=c++11 -verify %s -DUSER_DEFINED
   3 // RUN: %clang_cc1 -fsyntax-only -Wpessimizing-move -std=c++11 -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
   4
   5 // definitions for std::move
   6 namespace std {
   7 inline namespace foo {
   8 template <class T> struct remove_reference { typedef T type; };
   9 template <class T> struct remove_reference<T&> { typedef T type; };
  10 template <class T> struct remove_reference<T&&> { typedef T type; };
  11
  12 template <class T> typename remove_reference<T>::type &&move(T &&t);
  13 }
  14 }
  15
  16 struct A {
  17 #ifdef USER_DEFINED
  18   A() {}
  19   A(const A &) {}
  20   A(A &&) {}
  21   A &operator=(const A &) { return *this; }
  22   A &operator=(A &&) { return *this; }
  23 #endif
  24 };
  25 struct B {
  26   B() {}
  27   B(A) {}
  28 };
  29
  30 A test1(A a1) {
  31   A a2;
  32   return a1;
  33   return a2;
  34   return std::move(a1);
  35   return std::move(a2);
  36   // expected-warning@-1{{prevents copy elision}}
  37   // expected-note@-2{{remove std::move call}}
  38   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
  39   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
  40 }
  41
  42 B test2(A a1, B b1) {
  43   // Object is different than return type so don't warn.
  44   A a2;
  45   return a1;
  46   return a2;
  47   return std::move(a1);
  48   return std::move(a2);
  49
  50   B b2;
  51   return b1;
  52   return b2;
  53   return std::move(b1);
  54   return std::move(b2);
  55   // expected-warning@-1{{prevents copy elision}}
  56   // expected-note@-2{{remove std::move call}}
  57   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
  58   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
  59
  60   return A();
  61   return test1(a2);
  62   return std::move(A());
  63   // expected-warning@-1{{prevents copy elision}}
  64   // expected-note@-2{{remove std::move call}}
  65   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
  66   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
  67   return std::move(test1(a2));
  68   // expected-warning@-1{{prevents copy elision}}
  69   // expected-note@-2{{remove std::move call}}
  70   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
  71   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:29-[[@LINE-4]]:30}:""
  72 }
  73
  74 A global_a;
  75 A test3() {
  76   // Don't warn when object is not local.
  77   return global_a;
  78   return std::move(global_a);
  79   static A static_a;
  80   return static_a;
  81   return std::move(static_a);
  82
  83 }
  84
  85 A test4() {
  86   return A();
  87   return test3();
  88
  89   return std::move(A());
  90   // expected-warning@-1{{prevents copy elision}}
  91   // expected-note@-2{{remove std::move call}}
  92   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
  93   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
  94   return std::move(test3());
  95   // expected-warning@-1{{prevents copy elision}}
  96   // expected-note@-2{{remove std::move call}}
  97   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
  98   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:27-[[@LINE-4]]:28}:""
  99 }
 100
 101 void test5(A) {
 102   test5(A());
 103   test5(test4());
 104
 105   test5(std::move(A()));
 106   // expected-warning@-1{{prevents copy elision}}
 107   // expected-note@-2{{remove std::move call}}
 108   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:9-[[@LINE-3]]:19}:""
 109   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
 110   test5(std::move(test4()));
 111   // expected-warning@-1{{prevents copy elision}}
 112   // expected-note@-2{{remove std::move call}}
 113   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:9-[[@LINE-3]]:19}:""
 114   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:26-[[@LINE-4]]:27}:""
 115 }
 116
 117 void test6() {
 118   A a1 = A();
 119   A a2 = test3();
 120
 121   A a3 = std::move(A());
 122   // expected-warning@-1{{prevents copy elision}}
 123   // expected-note@-2{{remove std::move call}}
 124   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
 125   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
 126
 127   a3 = std::move(A());
 128   // expected-warning@-1{{prevents copy elision}}
 129   // expected-note@-2{{remove std::move call}}
 130   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:8-[[@LINE-3]]:18}:""
 131   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:21-[[@LINE-4]]:22}:""
 132
 133   A a4 = std::move(test3());
 134   // expected-warning@-1{{prevents copy elision}}
 135   // expected-note@-2{{remove std::move call}}
 136   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
 137   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:27-[[@LINE-4]]:28}:""
 138
 139   a4 = std::move(test3());
 140   // expected-warning@-1{{prevents copy elision}}
 141   // expected-note@-2{{remove std::move call}}
 142   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:8-[[@LINE-3]]:18}:""
 143   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:25-[[@LINE-4]]:26}:""
 144 }
 145
 146 A test7() {
 147   A a1 = std::move(A());
 148   // expected-warning@-1{{prevents copy elision}}
 149   // expected-note@-2{{remove std::move call}}
 150   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
 151   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
 152   A a2 = std::move((A()));
 153   // expected-warning@-1{{prevents copy elision}}
 154   // expected-note@-2{{remove std::move call}}
 155   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
 156   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:25-[[@LINE-4]]:26}:""
 157   A a3 = (std::move(A()));
 158   // expected-warning@-1{{prevents copy elision}}
 159   // expected-note@-2{{remove std::move call}}
 160   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:11-[[@LINE-3]]:21}:""
 161   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:24-[[@LINE-4]]:25}:""
 162   A a4 = (std::move((A())));
 163   // expected-warning@-1{{prevents copy elision}}
 164   // expected-note@-2{{remove std::move call}}
 165   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:11-[[@LINE-3]]:21}:""
 166   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:26-[[@LINE-4]]:27}:""
 167
 168   return std::move(a1);
 169   // expected-warning@-1{{prevents copy elision}}
 170   // expected-note@-2{{remove std::move call}}
 171   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
 172   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
 173   return std::move((a1));
 174   // expected-warning@-1{{prevents copy elision}}
 175   // expected-note@-2{{remove std::move call}}
 176   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
 177   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:24-[[@LINE-4]]:25}:""
 178   return (std::move(a1));
 179   // expected-warning@-1{{prevents copy elision}}
 180   // expected-note@-2{{remove std::move call}}
 181   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:11-[[@LINE-3]]:21}:""
 182   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
 183   return (std::move((a1)));
 184   // expected-warning@-1{{prevents copy elision}}
 185   // expected-note@-2{{remove std::move call}}
 186   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:11-[[@LINE-3]]:21}:""
 187   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:25-[[@LINE-4]]:26}:""
 188 }
 189
 190 #define wrap1(x) x
 191 #define wrap2(x) x
 192
 193 // Macro test. Since the std::move call is outside the macro, it is
 194 // safe to suggest a fix-it.
 195 A test8() {
 196   A a;
 197   return std::move(a);
 198   // expected-warning@-1{{prevents copy elision}}
 199   // expected-note@-2{{remove std::move call}}
 200   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
 201   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:21-[[@LINE-4]]:22}:""
 202   return std::move(wrap1(a));
 203   // expected-warning@-1{{prevents copy elision}}
 204   // expected-note@-2{{remove std::move call}}
 205   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
 206   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:28-[[@LINE-4]]:29}:""
 207   return std::move(wrap1(wrap2(a)));
 208   // expected-warning@-1{{prevents copy elision}}
 209   // expected-note@-2{{remove std::move call}}
 210   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
 211   // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:35-[[@LINE-4]]:36}:""
 212 }
 213
 214 #define test9            \
 215   A test9() {            \
 216     A a;                 \
 217     return std::move(a); \
 218   }
 219
 220 // Macro test.  The std::call is inside the macro, so no fix-it is suggested.
 221 test9
 222 // expected-warning@-1{{prevents copy elision}}
 223 // CHECK-NOT: fix-it
 224
 225 #define return_a return std::move(a)
 226
 227 // Macro test.  The std::call is inside the macro, so no fix-it is suggested.
 228 A test10() {
 229   A a;
 230   return_a;
 231   // expected-warning@-1{{prevents copy elision}}
 232   // CHECK-NOT: fix-it
 233 }
 234
 235 namespace templates {
 236   struct A {};
 237   struct B { B(A); };
 238
 239   // Warn once here since the type is not dependent.
 240   template <typename T>
 241   A test1() {
 242     A a;
 243     return std::move(a);
 244     // expected-warning@-1{{prevents copy elision}}
 245     // expected-note@-2{{remove std::move call}}
 246     // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:12-[[@LINE-3]]:22}:""
 247     // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
 248   }
 249   void run_test1() {
 250     test1<A>();
 251     test1<B>();
 252   }
 253
 254   // T1 and T2 may not be the same, the warning may not always apply.
 255   template <typename T1, typename T2>
 256   T1 test2() {
 257     T2 t;
 258     return std::move(t);
 259   }
 260   void run_test2() {
 261     test2<A, A>();
 262     test2<B, A>();
 263   }
 264 }