clang/test/SemaCXX/warn-loop-analysis.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -Wloop-analysis -verify -std=c++17 %s
   2
   3 struct S {
   4   bool stop() { return false; }
   5   bool keep_running;
   6 };
   7
   8 void by_ref(int &value) { }
   9 void by_value(int value) { }
  10 void by_pointer(int *value) {}
  11
  12 void test1() {
  13   S s;
  14   for (; !s.stop();) {}
  15   for (; s.keep_running;) {}
  16   for (int i; i < 1; ++i) {}
  17   for (int i; i < 1; ) {}  // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  18   for (int i; i < 1; ) { ++i; }
  19   for (int i; i < 1; ) { return; }
  20   for (int i; i < 1; ) { break; }
  21   for (int i; i < 1; ) { goto exit_loop; }
  22 exit_loop:
  23   for (int i; i < 1; ) { by_ref(i); }
  24   for (int i; i < 1; ) { by_value(i); }  // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  25   for (int i; i < 1; ) { by_pointer(&i); }
  26
  27   for (int i; i < 1; ++i)
  28     for (int j; j < 1; ++j)
  29       { }
  30   for (int i; i < 1; ++i)
  31     for (int j; j < 1; ++i)  // expected-warning {{variable 'j' used in loop condition not modified in loop body}}
  32       { }
  33   for (int i; i < 1; ++i)
  34     for (int j; i < 1; ++j)  // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  35       { }
  36
  37   for (int *i, *j; i < j; ++i) {}
  38   for (int *i, *j; i < j;) {}  // expected-warning {{variables 'i' and 'j' used in loop condition not modified in loop body}}
  39
  40   // Dereferencing pointers is ignored for now.
  41   for (int *i; *i; ) {}
  42 }
  43
  44 void test2() {
  45   int i, j, k;
  46   int *ptr;
  47
  48   // Testing CastExpr
  49   for (; i; ) {} // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  50   for (; i; ) { i = 5; }
  51
  52   // Testing BinaryOperator
  53   for (; i < j; ) {} // expected-warning {{variables 'i' and 'j' used in loop condition not modified in loop body}}
  54   for (; i < j; ) { i = 5; }
  55   for (; i < j; ) { j = 5; }
  56
  57   // Testing IntegerLiteral
  58   for (; i < 5; ) {} // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  59   for (; i < 5; ) { i = 5; }
  60
  61   // Testing FloatingLiteral
  62   for (; i < 5.0; ) {} // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  63   for (; i < 5.0; ) { i = 5; }
  64
  65   // Testing CharacterLiteral
  66   for (; i == 'a'; ) {} // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  67   for (; i == 'a'; ) { i = 5; }
  68
  69   // Testing CXXBoolLiteralExpr
  70   for (; i == true; ) {} // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  71   for (; i == true; ) { i = 5; }
  72
  73   // Testing GNUNullExpr
  74   for (; ptr == __null; ) {} // expected-warning {{variable 'ptr' used in loop condition not modified in loop body}}
  75   for (; ptr == __null; ) { ptr = &i; }
  76
  77   // Testing UnaryOperator
  78   for (; -i > 5; ) {} // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  79   for (; -i > 5; ) { ++i; }
  80
  81   // Testing ImaginaryLiteral
  82   for (; i != 3i; ) {} // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  83   for (; i != 3i; ) { ++i; }
  84
  85   // Testing ConditionalOperator
  86   for (; i ? j : k; ) {} // expected-warning {{variables 'i', 'j', and 'k' used in loop condition not modified in loop body}}
  87   for (; i ? j : k; ) { ++i; }
  88   for (; i ? j : k; ) { ++j; }
  89   for (; i ? j : k; ) { ++k; }
  90   for (; i; ) { j = i ? i : i; }  // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  91   for (; i; ) { j = (i = 1) ? i : i; }
  92   for (; i; ) { j = i ? i : ++i; }
  93
  94   // Testing BinaryConditionalOperator
  95   for (; i ?: j; ) {} // expected-warning {{variables 'i' and 'j' used in loop condition not modified in loop body}}
  96   for (; i ?: j; ) { ++i; }
  97   for (; i ?: j; ) { ++j; }
  98   for (; i; ) { j = i ?: i; }  // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
  99
 100   // Testing ParenExpr
 101   for (; (i); ) { }  // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
 102   for (; (i); ) { ++i; }
 103
 104   // Testing non-evaluated variables
 105   for (; i < sizeof(j); ) { }  // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
 106   for (; i < sizeof(j); ) { ++j; }  // expected-warning {{variable 'i' used in loop condition not modified in loop body}}
 107   for (; i < sizeof(j); ) { ++i; }
 108 }
 109
 110 // False positive and how to silence.
 111 void test3() {
 112   int x;
 113   int *ptr = &x;
 114   for (;x<5;) { *ptr = 6; }  // expected-warning {{variable 'x' used in loop condition not modified in loop body}}
 115
 116   for (;x<5;) {
 117     *ptr = 6;
 118     (void)x;
 119   }
 120 }
 121
 122 // Check ordering and printing of variables.  Max variables is currently 4.
 123 void test4() {
 124   int a, b, c, d, e, f;
 125   for (; a;);  // expected-warning {{variable 'a' used in loop condition not modified in loop body}}
 126   for (; a + b;);  // expected-warning {{variables 'a' and 'b' used in loop condition not modified in loop body}}
 127   for (; a + b + c;);  // expected-warning {{variables 'a', 'b', and 'c' used in loop condition not modified in loop body}}
 128   for (; a + b + c + d;);  // expected-warning {{variables 'a', 'b', 'c', and 'd' used in loop condition not modified in loop body}}
 129   for (; a + b + c + d + e;);  // expected-warning {{variables used in loop condition not modified in loop body}}
 130   for (; a + b + c + d + e + f;);  // expected-warning {{variables used in loop condition not modified in loop body}}
 131   for (; a + c + d + b;);  // expected-warning {{variables 'a', 'c', 'd', and 'b' used in loop condition not modified in loop body}}
 132   for (; d + c + b + a;);  // expected-warning {{variables 'd', 'c', 'b', and 'a' used in loop condition not modified in loop body}}
 133 }
 134
 135 // Ensure that the warning doesn't fail when lots of variables are used
 136 // in the conditional.
 137 void test5() {
 138   for (int a; a+a+a+a+a+a+a+a+a+a;); // \
 139    // expected-warning {{variable 'a' used in loop condition not modified in loop body}}
 140   for (int a; a+a+a+a+a+a+a+a+a+a+a;); // \
 141    // expected-warning {{variable 'a' used in loop condition not modified in loop body}}
 142   for (int a; a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a;);  // \
 143    // expected-warning {{variable 'a' used in loop condition not modified in loop body}}
 144   for (int a; a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a+a;);//\
 145    // expected-warning {{variable 'a' used in loop condition not modified in loop body}}
 146 }
 147
 148 // Ignore global variables and static variables.
 149 int x6;
 150 void test6() {
 151   static int y;
 152   for (;x6;);
 153   for (;y;);
 154 }
 155
 156 void test7() {
 157   int i;
 158   for (;;i++) {  // expected-note{{incremented here}}
 159     if (true) test7();
 160     i++;  // expected-warning{{incremented both}}
 161   }
 162   for (;;i++) {  // expected-note{{incremented here}}
 163     if (true) break;
 164     ++i;  // expected-warning{{incremented both}}
 165   }
 166   for (;;++i) {  // expected-note{{incremented here}}
 167     while (true) return;
 168     i++;  // expected-warning{{incremented both}}
 169   }
 170   for (;;++i) {  // expected-note{{incremented here}}
 171     ++i;  // expected-warning{{incremented both}}
 172   }
 173
 174   for (;;i--) {  // expected-note{{decremented here}}
 175     if (true) test7();
 176     i--;  // expected-warning{{decremented both}}
 177   }
 178   for (;;i--) {  // expected-note{{decremented here}}
 179     if (true) break;
 180     --i;  // expected-warning{{decremented both}}
 181   }
 182   for (;;--i) {  // expected-note{{decremented here}}
 183     while (true) return;
 184     i--;  // expected-warning{{decremented both}}
 185   }
 186   for (;;--i) {  // expected-note{{decremented here}}
 187     --i;  // expected-warning{{decremented both}}
 188   }
 189
 190   // Don't warn when loop is only one statement.
 191   for (;;++i)
 192     i++;
 193   for (;;--i)
 194     --i;
 195
 196   // Don't warn when loop has continue statement.
 197   for (;;i++) {
 198     if (true) continue;
 199     i++;
 200   }
 201   for (;;i--) {
 202     if (true) continue;
 203     i--;
 204   }
 205
 206   // But do warn if the continue is in a nested loop.
 207   for (;;i--) { // expected-note{{decremented here}}
 208     for (int j = 0; j < 10; ++j) continue;
 209     i--; // expected-warning{{decremented both}}
 210   }
 211 }
 212
 213 struct iterator {
 214   iterator operator++() { return *this; }
 215   iterator operator++(int) { return *this; }
 216   iterator operator--() { return *this; }
 217   iterator operator--(int) { return *this; }
 218 };
 219 void test8() {
 220   iterator i;
 221   for (;;i++) {  // expected-note{{incremented here}}
 222     if (true) test7();
 223     i++;  // expected-warning{{incremented both}}
 224   }
 225   for (;;i++) {  // expected-note{{incremented here}}
 226     if (true) break;
 227     ++i;  // expected-warning{{incremented both}}
 228   }
 229   for (;;++i) {  // expected-note{{incremented here}}
 230     while (true) return;
 231     i++;  // expected-warning{{incremented both}}
 232   }
 233   for (;;++i) {  // expected-note{{incremented here}}
 234     ++i;  // expected-warning{{incremented both}}
 235   }
 236
 237   for (;;i--) {  // expected-note{{decremented here}}
 238     if (true) test7();
 239     i--;  // expected-warning{{decremented both}}
 240   }
 241   for (;;i--) {  // expected-note{{decremented here}}
 242     if (true) break;
 243     --i;  // expected-warning{{decremented both}}
 244   }
 245   for (;;--i) {  // expected-note{{decremented here}}
 246     while (true) return;
 247     i--;  // expected-warning{{decremented both}}
 248   }
 249   for (;;--i) {  // expected-note{{decremented here}}
 250     --i;  // expected-warning{{decremented both}}
 251   }
 252
 253   // Don't warn when loop is only one statement.
 254   for (;;++i)
 255     i++;
 256   for (;;--i)
 257     --i;
 258
 259   // Don't warn when loop has continue statement.
 260   for (;;i++) {
 261     if (true) continue;
 262     i++;
 263   }
 264   for (;;i--) {
 265     if (true) continue;
 266     i--;
 267   }
 268
 269   // But do warn if the continue is in a nested loop.
 270   for (;;i--) { // expected-note{{decremented here}}
 271     for (int j = 0; j < 10; ++j) continue;
 272     i--; // expected-warning{{decremented both}}
 273   }
 274 }
 275
 276 int f(int);
 277 void test9() {
 278   // Don't warn when variable is defined by the loop condition.
 279   for (int i = 0; int x = f(i); ++i) {}
 280 }
 281
 282 // Don't warn when decomposition variables are in the loop condition.
 283 // TODO: BindingDecl's which make a copy should warn.
 284 void test10() {
 285   int arr[] = {1, 2, 3};
 286   for (auto[i, j, k] = arr;;) { }
 287   for (auto[i, j, k] = arr; i < j; ++i, ++j) { }
 288
 289   for (auto[i, j, k] = arr; i;) { }
 290   for (auto[i, j, k] = arr; i < j;) { }
 291   for (auto[i, j, k] = arr; i < j; ++arr[0]) { }
 292
 293   int a = 1, b = 2;
 294   for (auto[i, j, k] = arr; a < b;) { }  // expected-warning{{variables 'a' and 'b' used in loop condition not modified in loop body}}
 295   for (auto[i, j, k] = arr; a < b; ++a) { }
 296
 297   for (auto [i, j, k] = arr; i < a;) { }
 298   for (auto[i, j, k] = arr; i < a; ++a) { }
 299   for (auto[i, j, k] = arr; i < a; ++i) { }
 300   for (auto[i, j, k] = arr; i < a; ++arr[0]) { }
 301 };