clang/test/Analysis/dead-stores.c

   1 // RUN: %check_analyzer_fixit %s %t \
   2 // RUN:   -Wunused-variable -fblocks -Wno-unreachable-code \
   3 // RUN:   -analyzer-checker=core,deadcode.DeadStores \
   4 // RUN:   -analyzer-config deadcode.DeadStores:ShowFixIts=true \
   5 // RUN:   -analyzer-config \
   6 // RUN:       deadcode.DeadStores:WarnForDeadNestedAssignments=false \
   7 // RUN:   -verify=non-nested
   8
   9 // RUN: %check_analyzer_fixit %s %t \
  10 // RUN:   -Wunused-variable -fblocks -Wno-unreachable-code \
  11 // RUN:   -analyzer-checker=core,deadcode.DeadStores \
  12 // RUN:   -analyzer-config deadcode.DeadStores:ShowFixIts=true \
  13 // RUN:   -verify=non-nested,nested
  14
  15 extern int printf(const char *, ...);
  16
  17 void f1(void) {
  18   int k, y; // non-nested-warning {{unused variable 'k'}}
  19             // non-nested-warning@-1 {{unused variable 'y'}}
  20   int abc = 1;
  21   long idx = abc + 3 * 5; // non-nested-warning {{never read}}
  22                           // non-nested-warning@-1 {{unused variable 'idx'}}
  23   // CHECK-FIXES:      int abc = 1;
  24   // CHECK-FIXES-NEXT: long idx;
  25 }
  26
  27 void f2(void *b) {
  28   char *c = (char *)b; // no-warning
  29   char *d = b + 1;     // non-nested-warning {{never read}}
  30                        // non-nested-warning@-1 {{unused variable 'd'}}
  31   // CHECK-FIXES:      char *c = (char *)b;
  32   // CHECK-FIXES-NEXT: char *d;
  33
  34   printf("%s", c);
  35 }
  36
  37 int f(void);
  38 void f3(void) {
  39   int r;
  40   if ((r = f()) != 0) { // no-warning
  41     int y = r;          // no-warning
  42     printf("the error is: %d\n", y);
  43   }
  44 }
  45
  46 void f4(int k) {
  47   k = 1;
  48   if (k)
  49     f1();
  50   k = 2; // non-nested-warning {{never read}}
  51 }
  52
  53 void f5(void) {
  54   int x = 4;   // no-warning
  55   int *p = &x; // non-nested-warning {{never read}}
  56                // non-nested-warning@-1 {{unused variable 'p'}}
  57   // CHECK-FIXES:      int x = 4;
  58   // CHECK-FIXES-NEXT: int *p;
  59 }
  60
  61 int f6(void) {
  62   int x = 4;
  63   ++x; // no-warning
  64   return 1;
  65 }
  66
  67 int f7(int *p) {
  68   // This is allowed for defensive programming.
  69   p = 0; // no-warning
  70   return 1;
  71 }
  72
  73 int f7b(int *p) {
  74   // This is allowed for defensive programming.
  75   p = (0); // no-warning
  76   return 1;
  77 }
  78
  79 int f7c(int *p) {
  80   // This is allowed for defensive programming.
  81   p = (void *)0; // no-warning
  82   return 1;
  83 }
  84
  85 int f7d(int *p) {
  86   // This is allowed for defensive programming.
  87   p = (void *)(0); // no-warning
  88   return 1;
  89 }
  90
  91 // Warn for dead stores in nested expressions.
  92 int f8(int *p) {
  93   extern int *baz(void);
  94   if ((p = baz())) // nested-warning {{Although the value stored}}
  95     return 1;
  96   return 0;
  97 }
  98
  99 int f9(void) {
 100   int x = 4;
 101   x = x + 10; // non-nested-warning {{never read}}
 102   return 1;
 103 }
 104
 105 int f10(void) {
 106   int x = 4;
 107   x = 10 + x; // non-nested-warning {{never read}}
 108   return 1;
 109 }
 110
 111 int f11(void) {
 112   int x = 4;
 113   return x++; // non-nested-warning {{never read}}
 114 }
 115
 116 int f11b(void) {
 117   int x = 4;
 118   return ((((++x)))); // no-warning
 119 }
 120
 121 int f12a(int y) {
 122   int x = y; // non-nested-warning {{unused variable 'x'}}
 123   return 1;
 124 }
 125
 126 int f12b(int y) {
 127   int x __attribute__((unused)) = y; // no-warning
 128   return 1;
 129 }
 130
 131 int f12c(int y) {
 132   // Allow initialiation of scalar variables by parameters as a form of
 133   // defensive programming.
 134   int x = y; // no-warning
 135   x = 1;
 136   return x;
 137 }
 138
 139 // Filed with PR 2630.  This code should produce no warnings.
 140 int f13(void) {
 141   int a = 1;
 142   int b, c = b = a + a;
 143
 144   if (b > 0)
 145     return (0);
 146   return (a + b + c);
 147 }
 148
 149 // Filed with PR 2763.
 150 int f14(int count) {
 151   int index, nextLineIndex;
 152   for (index = 0; index < count; index = nextLineIndex + 1) {
 153     nextLineIndex = index + 1; // no-warning
 154     continue;
 155   }
 156   return index;
 157 }
 158
 159 void f15(unsigned x, unsigned y) {
 160   int count = x * y; // no-warning
 161   int z[count];      // non-nested-warning {{unused variable 'z'}}
 162 }
 163
 164 // Warn for dead stores in nested expressions.
 165 int f16(int x) {
 166   x = x * 2;
 167   x = sizeof(int[x = (x || x + 1) * 2]) ? 5 : 8;
 168   // nested-warning@-1 {{Although the value stored}}
 169   return x;
 170 }
 171
 172 // Self-assignments should not be flagged as dead stores.
 173 void f17(void) {
 174   int x = 1;
 175   x = x;
 176 }
 177
 178 // The values of dead stores are only "consumed" in an enclosing expression
 179 // what that value is actually used.  In other words, don't say "Although the
 180 // value stored to 'x' is used...".
 181 int f18(void) {
 182   int x = 0; // no-warning
 183   if (1)
 184     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
 185   while (1)
 186     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
 187   // unreachable.
 188   do
 189     x = 10; // no-warning
 190   while (1);
 191   return (x = 10); // no-warning
 192 }
 193
 194 int f18_a(void) {
 195   int x = 0;       // no-warning
 196   return (x = 10); // nested-warning {{Although the value stored}}
 197 }
 198
 199 void f18_b(void) {
 200   int x = 0; // no-warning
 201   if (1)
 202     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
 203 }
 204
 205 void f18_c(void) {
 206   int x = 0;
 207   while (1)
 208     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
 209 }
 210
 211 void f18_d(void) {
 212   int x = 0; // no-warning
 213   do
 214     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
 215   while (1);
 216 }
 217
 218 // PR 3514: false positive `dead initialization` warning for init to global
 219 //  http://llvm.org/bugs/show_bug.cgi?id=3514
 220 extern const int MyConstant;
 221 int f19(void) {
 222   int x = MyConstant; // no-warning
 223   x = 1;
 224   return x;
 225 }
 226
 227 int f19b(void) { // This case is the same as f19.
 228   const int MyConstant = 0;
 229   int x = MyConstant; // no-warning
 230   x = 1;
 231   return x;
 232 }
 233
 234 void f20(void) {
 235   int x = 1; // no-warning
 236 #pragma unused(x)
 237 }
 238
 239 void halt(void) __attribute__((noreturn));
 240 int f21(void) {
 241   int x = 4;
 242   x = x + 1; // non-nested-warning {{never read}}
 243   if (1) {
 244     halt();
 245     (void)x;
 246   }
 247   return 1;
 248 }
 249
 250 int j;
 251 void f22(void) {
 252   int x = 4;
 253   int y1 = 4;
 254   int y2 = 4;
 255   int y3 = 4;
 256   int y4 = 4;
 257   int y5 = 4;
 258   int y6 = 4;
 259   int y7 = 4;
 260   int y8 = 4;
 261   int y9 = 4;
 262   int y10 = 4;
 263   int y11 = 4;
 264   int y12 = 4;
 265   int y13 = 4;
 266   int y14 = 4;
 267   int y15 = 4;
 268   int y16 = 4;
 269   int y17 = 4;
 270   int y18 = 4;
 271   int y19 = 4;
 272   int y20 = 4;
 273
 274   x = x + 1; // non-nested-warning {{never read}}
 275   ++y1;
 276   ++y2;
 277   ++y3;
 278   ++y4;
 279   ++y5;
 280   ++y6;
 281   ++y7;
 282   ++y8;
 283   ++y9;
 284   ++y10;
 285   ++y11;
 286   ++y12;
 287   ++y13;
 288   ++y14;
 289   ++y15;
 290   ++y16;
 291   ++y17;
 292   ++y18;
 293   ++y19;
 294   ++y20;
 295
 296   switch (j) {
 297   case 1:
 298     if (0)
 299       (void)x;
 300     if (1) {
 301       (void)y1;
 302       return;
 303     }
 304     (void)x;
 305     break;
 306   case 2:
 307     if (0)
 308       (void)x;
 309     else {
 310       (void)y2;
 311       return;
 312     }
 313     (void)x;
 314     break;
 315   case 3:
 316     if (1) {
 317       (void)y3;
 318       return;
 319     } else
 320       (void)x;
 321     (void)x;
 322     break;
 323   case 4:
 324     0 ?: ((void)y4, ({ return; }));
 325     (void)x;
 326     break;
 327   case 5:
 328     1 ?: (void)x;
 329     0 ? (void)x : ((void)y5, ({ return; }));
 330     (void)x;
 331     break;
 332   case 6:
 333     1 ? ((void)y6, ({ return; })) : (void)x;
 334     (void)x;
 335     break;
 336   case 7:
 337     (void)(0 && x);
 338     (void)y7;
 339     (void)(0 || (y8, ({ return; }), 1));
 340     // non-nested-warning@-1 {{left operand of comma operator has no effect}}
 341     (void)x;
 342     break;
 343   case 8:
 344     (void)(1 && (y9, ({ return; }), 1));
 345     // non-nested-warning@-1 {{left operand of comma operator has no effect}}
 346     (void)x;
 347     break;
 348   case 9:
 349     (void)(1 || x);
 350     (void)y10;
 351     break;
 352   case 10:
 353     while (0) {
 354       (void)x;
 355     }
 356     (void)y11;
 357     break;
 358   case 11:
 359     while (1) {
 360       (void)y12;
 361     }
 362     (void)x;
 363     break;
 364   case 12:
 365     do {
 366       (void)y13;
 367     } while (0);
 368     (void)y14;
 369     break;
 370   case 13:
 371     do {
 372       (void)y15;
 373     } while (1);
 374     (void)x;
 375     break;
 376   case 14:
 377     for (;;) {
 378       (void)y16;
 379     }
 380     (void)x;
 381     break;
 382   case 15:
 383     for (; 1;) {
 384       (void)y17;
 385     }
 386     (void)x;
 387     break;
 388   case 16:
 389     for (; 0;) {
 390       (void)x;
 391     }
 392     (void)y18;
 393     break;
 394   case 17:
 395     __builtin_choose_expr(0, (void)x, ((void)y19, ({ return; })));
 396     (void)x;
 397     break;
 398   case 19:
 399     __builtin_choose_expr(1, ((void)y20, ({ return; })), (void)x);
 400     (void)x;
 401     break;
 402   }
 403 }
 404
 405 void f23_aux(const char *s);
 406 void f23(int argc, char **argv) {
 407   int shouldLog = (argc > 1); // no-warning
 408   ^{
 409     if (shouldLog)
 410       f23_aux("I did too use it!\n");
 411     else
 412       f23_aux("I shouldn't log.  Wait.. d'oh!\n");
 413   }();
 414 }
 415
 416 void f23_pos(int argc, char **argv) {
 417   int shouldLog = (argc > 1);
 418   // non-nested-warning@-1 {{Value stored to 'shouldLog' during its initialization is never read}}
 419   // non-nested-warning@-2 {{unused variable 'shouldLog'}}
 420   // CHECK-FIXES:      void f23_pos(int argc, char **argv) {
 421   // CHECK-FIXES-NEXT:   int shouldLog;
 422   ^{
 423     f23_aux("I did too use it!\n");
 424   }();
 425 }
 426
 427 void f24_A(int y) {
 428   // FIXME: One day this should be reported as dead since 'z = x + y' is dead.
 429   int x = (y > 2); // no-warning
 430   ^{
 431     int z = x + y;
 432     // non-nested-warning@-1 {{Value stored to 'z' during its initialization is never read}}
 433     // non-nested-warning@-2 {{unused variable 'z'}}
 434     // CHECK-FIXES:      void f24_A(int y) {
 435     // CHECK-FIXES-NEXT:   //
 436     // CHECK-FIXES-NEXT:   int x = (y > 2);
 437     // CHECK-FIXES-NEXT:   ^{
 438     // CHECK-FIXES-NEXT:     int z;
 439   }();
 440 }
 441
 442 void f24_B(int y) {
 443   // FIXME: One day this should be reported as dead since 'x' is just overwritten.
 444   __block int x = (y > 2); // no-warning
 445   ^{
 446     // FIXME: This should eventually be a dead store since it is never read either.
 447     x = 5; // no-warning
 448   }();
 449 }
 450
 451 int f24_C(int y) {
 452   // FIXME: One day this should be reported as dead since 'x' is just overwritten.
 453   __block int x = (y > 2); // no-warning
 454   ^{
 455     x = 5; // no-warning
 456   }();
 457   return x;
 458 }
 459
 460 int f24_D(int y) {
 461   __block int x = (y > 2); // no-warning
 462   ^{
 463     if (y > 4)
 464       x = 5; // no-warning
 465   }();
 466   return x;
 467 }
 468
 469 // This example shows that writing to a variable captured by a block means that
 470 // it might not be dead.
 471 int f25(int y) {
 472   __block int x = (y > 2);
 473   __block int z = 0;
 474   void (^foo)(void) = ^{
 475     z = x + y;
 476   };
 477   x = 4; // no-warning
 478   foo();
 479   return z;
 480 }
 481
 482 // This test is mostly the same as 'f25', but shows that the heuristic of
 483 // pruning out dead stores for variables that are just marked '__block' is
 484 // overly conservative.
 485 int f25_b(int y) {
 486   // FIXME: we should eventually report a dead store here.
 487   __block int x = (y > 2);
 488   __block int z = 0;
 489   x = 4; // no-warning
 490   return z;
 491 }
 492
 493 int f26_nestedblocks(void) {
 494   int z;
 495   z = 1;
 496   __block int y = 0;
 497   ^{
 498     int k;
 499     k = 1; // non-nested-warning {{Value stored to 'k' is never read}}
 500     ^{
 501       y = z + 1;
 502     }();
 503   }();
 504   return y;
 505 }
 506
 507 // The FOREACH macro in QT uses 'break' statements within statement expressions
 508 // placed within the increment code of for loops.
 509 void rdar8014335(void) {
 510   for (int i = 0 ; i != 10 ; ({ break; })) {
 511     for (;; ({ ++i; break; }))
 512       ;
 513     // non-nested-warning@-2 {{'break' is bound to current loop, GCC binds it to the enclosing loop}}
 514     // Note that the next value stored to 'i' is never executed
 515     // because the next statement to be executed is the 'break'
 516     // in the increment code of the first loop.
 517     i = i * 3; // non-nested-warning {{Value stored to 'i' is never read}}
 518   }
 519 }
 520
 521 // NullStmts followed by do...while() can lead to disconnected CFG
 522 //
 523 // This previously caused bogus dead-stores warnings because the body of the first do...while was
 524 // disconnected from the entry of the function.
 525 typedef struct { float r; float i; } s_rdar8320674;
 526 typedef struct { s_rdar8320674 x[1]; } s2_rdar8320674;
 527
 528 void rdar8320674(s_rdar8320674 *z, unsigned y, s2_rdar8320674 *st, int m)
 529 {
 530     s_rdar8320674 * z2;
 531     s_rdar8320674 * tw1 = st->x;
 532     s_rdar8320674 t;
 533     z2 = z + m;
 534     do{
 535         ; ;
 536         do{ (t).r = (*z2).r*(*tw1).r - (*z2).i*(*tw1).i; (t).i = (*z2).r*(*tw1).i + (*z2).i*(*tw1).r; }while(0);
 537         tw1 += y;
 538         do { (*z2).r=(*z).r-(t).r; (*z2).i=(*z).i-(t).i; }while(0);
 539         do { (*z).r += (t).r; (*z).i += (t).i; }while(0);
 540         ++z2;
 541         ++z;
 542     }while (--m);
 543 }
 544
 545 // Avoid dead stores resulting from an assignment (and use) being unreachable.
 546 void rdar8405222_aux(int i);
 547 void rdar8405222(void) {
 548   const int show = 0;
 549   int i = 0;
 550   if (show)
 551     i = 5; // no-warning
 552   if (show)
 553     rdar8405222_aux(i);
 554 }
 555
 556 // Look through chains of assignments, e.g.: int x = y = 0, when employing
 557 // silencing heuristics.
 558 int radar11185138_foo(void) {
 559   int x, y;
 560   x = y = 0; // non-nested-warning {{never read}}
 561   return y;
 562 }
 563
 564 int rdar11185138_bar(void) {
 565   int y;
 566   int x = y = 0; // nested-warning {{Although the value stored}}
 567   x = 2;
 568   y = 2;
 569   return x + y;
 570 }
 571
 572 int *radar11185138_baz(void) {
 573   int *x, *y;
 574   x = y = 0; // no-warning
 575   return y;
 576 }
 577
 578 int getInt(void);
 579 int *getPtr(void);
 580 void testBOComma(void) {
 581   int x0 = (getInt(), 0); // non-nested-warning {{unused variable 'x0'}}
 582   int x1 = (getInt(), getInt());
 583   // non-nested-warning@-1 {{Value stored to 'x1' during its initialization is never read}}
 584   // non-nested-warning@-2 {{unused variable 'x1'}}
 585
 586   int x2 = (getInt(), getInt(), getInt());
 587   // non-nested-warning@-1 {{Value stored to 'x2' during its initialization is never read}}
 588   // non-nested-warning@-2 {{unused variable 'x2'}}
 589
 590   int x3;
 591   x3 = (getInt(), getInt(), 0);
 592   // non-nested-warning@-1 {{Value stored to 'x3' is never read}}
 593
 594   int x4 = (getInt(), (getInt(), 0));
 595   // non-nested-warning@-1 {{unused variable 'x4'}}
 596
 597   int y;
 598   int x5 = (getInt(), (y = 0));
 599   // non-nested-warning@-1 {{unused variable 'x5'}}
 600   // nested-warning@-2 {{Although the value stored}}
 601
 602   int x6 = (getInt(), (y = getInt()));
 603   // non-nested-warning@-1 {{Value stored to 'x6' during its initialization is never read}}
 604   // non-nested-warning@-2 {{unused variable 'x6'}}
 605   // nested-warning@-3 {{Although the value stored}}
 606
 607   int x7 = 0, x8 = getInt();
 608   // non-nested-warning@-1 {{Value stored to 'x8' during its initialization is never read}}
 609   // non-nested-warning@-2 {{unused variable 'x8'}}
 610   // non-nested-warning@-3 {{unused variable 'x7'}}
 611
 612   int x9 = getInt(), x10 = 0;
 613   // non-nested-warning@-1 {{Value stored to 'x9' during its initialization is never read}}
 614   // non-nested-warning@-2 {{unused variable 'x9'}}
 615   // non-nested-warning@-3 {{unused variable 'x10'}}
 616
 617   int m = getInt(), mm, mmm;
 618   // non-nested-warning@-1 {{Value stored to 'm' during its initialization is never read}}
 619   // non-nested-warning@-2 {{unused variable 'm'}}
 620   // non-nested-warning@-3 {{unused variable 'mm'}}
 621   // non-nested-warning@-4 {{unused variable 'mmm'}}
 622
 623   int n, nn = getInt();
 624   // non-nested-warning@-1 {{Value stored to 'nn' during its initialization is never read}}
 625   // non-nested-warning@-2 {{unused variable 'n'}}
 626   // non-nested-warning@-3 {{unused variable 'nn'}}
 627
 628   int *p;
 629   p = (getPtr(), (int *)0); // no warning
 630 }
 631
 632 void testVolatile(void) {
 633   volatile int v;
 634   v = 0; // no warning
 635 }
 636
 637 struct Foo {
 638   int x;
 639   int y;
 640 };
 641
 642 struct Foo rdar34122265_getFoo(void);
 643
 644 int rdar34122265_test(int input) {
 645   // This is allowed for defensive programming.
 646   struct Foo foo = {0, 0};
 647   if (input > 0) {
 648     foo = rdar34122265_getFoo();
 649   } else {
 650     return 0;
 651   }
 652   return foo.x + foo.y;
 653 }
 654
 655 void rdar34122265_test_cast(void) {
 656   // This is allowed for defensive programming.
 657   struct Foo foo = {0, 0};
 658   (void)foo;
 659 }
 660
 661 struct Bar {
 662   struct Foo x, y;
 663 };
 664
 665 struct Bar rdar34122265_getBar(void);
 666
 667 int rdar34122265_test_nested(int input) {
 668   // This is allowed for defensive programming.
 669   struct Bar bar = {{0, 0}, {0, 0}};
 670   if (input > 0) {
 671     bar = rdar34122265_getBar();
 672   } else {
 673     return 0;
 674   }
 675   return bar.x.x + bar.y.y;
 676 }