test/Analysis/dead-stores.c - clang - Git at Google

 // RUN: %clang_analyze_cc1 -Wunused-variable -fblocks -Wno-unreachable-code \
 // RUN:   -analyzer-checker=core,deadcode.DeadStores \
 // RUN:   -analyzer-config deadcode.DeadStores:ShowFixIts=true \
 // RUN:   -analyzer-config fixits-as-remarks=true \
 // RUN:   -analyzer-config \
 // RUN:       deadcode.DeadStores:WarnForDeadNestedAssignments=false \
 // RUN:   -verify=non-nested %s

 // RUN: %clang_analyze_cc1 -Wunused-variable -fblocks -Wno-unreachable-code \
 // RUN:   -analyzer-checker=core,deadcode.DeadStores \
 // RUN:   -analyzer-config deadcode.DeadStores:ShowFixIts=true \
 // RUN:   -analyzer-config fixits-as-remarks=true \
 // RUN:   -verify=non-nested,nested %s

 void f1() {
   int k, y; // non-nested-warning {{unused variable 'k'}}
             // non-nested-warning@-1 {{unused variable 'y'}}
   int abc = 1;
   long idx = abc + 3 * 5; // non-nested-warning {{never read}}
                           // non-nested-warning@-1 {{unused variable 'idx'}}
                           // non-nested-remark@-2 {{11-24: ''}}
 }

 void f2(void *b) {
   char *c = (char *)b; // no-warning
   char *d = b + 1;     // non-nested-warning {{never read}}
                        // non-nested-warning@-1 {{unused variable 'd'}}
                        // non-nested-remark@-2 {{10-17: ''}}
   printf("%s", c);
   // non-nested-warning@-1 {{implicitly declaring library function 'printf' with type 'int (const char *, ...)'}}
   // non-nested-note@-2 {{include the header <stdio.h> or explicitly provide a declaration for 'printf'}}
 }

 int f();
 void f3() {
   int r;
   if ((r = f()) != 0) { // no-warning
     int y = r;          // no-warning
     printf("the error is: %d\n", y);
   }
 }

 void f4(int k) {
   k = 1;
   if (k)
     f1();
   k = 2; // non-nested-warning {{never read}}
 }

 void f5() {
   int x = 4;   // no-warning
   int *p = &x; // non-nested-warning {{never read}}
                // non-nested-warning@-1 {{unused variable 'p'}}
                // non-nested-remark@-2 {{9-13: ''}}
 }

 int f6() {
   int x = 4;
   ++x; // no-warning
   return 1;
 }

 int f7(int *p) {
   // This is allowed for defensive programming.
   p = 0; // no-warning
   return 1;
 }

 int f7b(int *p) {
   // This is allowed for defensive programming.
   p = (0); // no-warning
   return 1;
 }

 int f7c(int *p) {
   // This is allowed for defensive programming.
   p = (void *)0; // no-warning
   return 1;
 }

 int f7d(int *p) {
   // This is allowed for defensive programming.
   p = (void *)(0); // no-warning
   return 1;
 }

 // Warn for dead stores in nested expressions.
 int f8(int *p) {
   extern int *baz();
   if ((p = baz())) // nested-warning {{Although the value stored}}
     return 1;
   return 0;
 }

 int f9() {
   int x = 4;
   x = x + 10; // non-nested-warning {{never read}}
   return 1;
 }

 int f10() {
   int x = 4;
   x = 10 + x; // non-nested-warning {{never read}}
   return 1;
 }

 int f11() {
   int x = 4;
   return x++; // non-nested-warning {{never read}}
 }

 int f11b() {
   int x = 4;
   return ((((++x)))); // no-warning
 }

 int f12a(int y) {
   int x = y; // non-nested-warning {{unused variable 'x'}}
   return 1;
 }

 int f12b(int y) {
   int x __attribute__((unused)) = y; // no-warning
   return 1;
 }

 int f12c(int y) {
   // Allow initialiation of scalar variables by parameters as a form of
   // defensive programming.
   int x = y; // no-warning
   x = 1;
   return x;
 }

 // Filed with PR 2630.  This code should produce no warnings.
 int f13(void) {
   int a = 1;
   int b, c = b = a + a;

   if (b > 0)
     return (0);
   return (a + b + c);
 }

 // Filed with PR 2763.
 int f14(int count) {
   int index, nextLineIndex;
   for (index = 0; index < count; index = nextLineIndex + 1) {
     nextLineIndex = index + 1; // no-warning
     continue;
   }
   return index;
 }

 // Test case for <rdar://problem/6248086>
 void f15(unsigned x, unsigned y) {
   int count = x * y; // no-warning
   int z[count];      // non-nested-warning {{unused variable 'z'}}
 }

 // Warn for dead stores in nested expressions.
 int f16(int x) {
   x = x * 2;
   x = sizeof(int[x = (x || x + 1) * 2]) ? 5 : 8;
   // nested-warning@-1 {{Although the value stored}}
   return x;
 }

 // Self-assignments should not be flagged as dead stores.
 void f17() {
   int x = 1;
   x = x;
 }

 // <rdar://problem/6506065>
 // The values of dead stores are only "consumed" in an enclosing expression
 // what that value is actually used.  In other words, don't say "Although the
 // value stored to 'x' is used...".
 int f18() {
   int x = 0; // no-warning
   if (1)
     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
   while (1)
     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
   // unreachable.
   do
     x = 10; // no-warning
   while (1);
   return (x = 10); // no-warning
 }

 int f18_a() {
   int x = 0;       // no-warning
   return (x = 10); // nested-warning {{Although the value stored}}
 }

 void f18_b() {
   int x = 0; // no-warning
   if (1)
     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
 }

 void f18_c() {
   int x = 0;
   while (1)
     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
 }

 void f18_d() {
   int x = 0; // no-warning
   do
     x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
   while (1);
 }

 // PR 3514: false positive `dead initialization` warning for init to global
 //  http://llvm.org/bugs/show_bug.cgi?id=3514
 extern const int MyConstant;
 int f19(void) {
   int x = MyConstant; // no-warning
   x = 1;
   return x;
 }

 int f19b(void) { // This case is the same as f19.
   const int MyConstant = 0;
   int x = MyConstant; // no-warning
   x = 1;
   return x;
 }

 void f20(void) {
   int x = 1; // no-warning
 #pragma unused(x)
 }

 void halt() __attribute__((noreturn));
 int f21() {
   int x = 4;
   x = x + 1; // non-nested-warning {{never read}}
   if (1) {
     halt();
     (void)x;
   }
   return 1;
 }

 int j;
 void f22() {
   int x = 4;
   int y1 = 4;
   int y2 = 4;
   int y3 = 4;
   int y4 = 4;
   int y5 = 4;
   int y6 = 4;
   int y7 = 4;
   int y8 = 4;
   int y9 = 4;
   int y10 = 4;
   int y11 = 4;
   int y12 = 4;
   int y13 = 4;
   int y14 = 4;
   int y15 = 4;
   int y16 = 4;
   int y17 = 4;
   int y18 = 4;
   int y19 = 4;
   int y20 = 4;

   x = x + 1; // non-nested-warning {{never read}}
   ++y1;
   ++y2;
   ++y3;
   ++y4;
   ++y5;
   ++y6;
   ++y7;
   ++y8;
   ++y9;
   ++y10;
   ++y11;
   ++y12;
   ++y13;
   ++y14;
   ++y15;
   ++y16;
   ++y17;
   ++y18;
   ++y19;
   ++y20;

   switch (j) {
   case 1:
     if (0)
       (void)x;
     if (1) {
       (void)y1;
       return;
     }
     (void)x;
     break;
   case 2:
     if (0)
       (void)x;
     else {
       (void)y2;
       return;
     }
     (void)x;
     break;
   case 3:
     if (1) {
       (void)y3;
       return;
     } else
       (void)x;
     (void)x;
     break;
   case 4:
     0 ?: ((void)y4, ({ return; }));
     (void)x;
     break;
   case 5:
     1 ?: (void)x;
     0 ? (void)x : ((void)y5, ({ return; }));
     (void)x;
     break;
   case 6:
     1 ? ((void)y6, ({ return; })) : (void)x;
     (void)x;
     break;
   case 7:
     (void)(0 && x);
     (void)y7;
     (void)(0 || (y8, ({ return; }), 1));
     // non-nested-warning@-1 {{expression result unused}}
     (void)x;
     break;
   case 8:
     (void)(1 && (y9, ({ return; }), 1));
     // non-nested-warning@-1 {{expression result unused}}
     (void)x;
     break;
   case 9:
     (void)(1 || x);
     (void)y10;
     break;
   case 10:
     while (0) {
       (void)x;
     }
     (void)y11;
     break;
   case 11:
     while (1) {
       (void)y12;
     }
     (void)x;
     break;
   case 12:
     do {
       (void)y13;
     } while (0);
     (void)y14;
     break;
   case 13:
     do {
       (void)y15;
     } while (1);
     (void)x;
     break;
   case 14:
     for (;;) {
       (void)y16;
     }
     (void)x;
     break;
   case 15:
     for (; 1;) {
       (void)y17;
     }
     (void)x;
     break;
   case 16:
     for (; 0;) {
       (void)x;
     }
     (void)y18;
     break;
   case 17:
     __builtin_choose_expr(0, (void)x, ((void)y19, ({ return; })));
     (void)x;
     break;
   case 19:
     __builtin_choose_expr(1, ((void)y20, ({ return; })), (void)x);
     (void)x;
     break;
   }
 }

 void f23_aux(const char *s);
 void f23(int argc, char **argv) {
   int shouldLog = (argc > 1); // no-warning
   ^{
     if (shouldLog)
       f23_aux("I did too use it!\n");
     else
       f23_aux("I shouldn't log.  Wait.. d'oh!\n");
   }();
 }

 void f23_pos(int argc, char **argv) {
   int shouldLog = (argc > 1);
   // non-nested-warning@-1 {{Value stored to 'shouldLog' during its initialization is never read}}
   // non-nested-warning@-2 {{unused variable 'shouldLog'}}
   // non-nested-remark@-3 {{16-28: ''}}
   ^{
     f23_aux("I did too use it!\n");
   }();
 }

 void f24_A(int y) {
   // FIXME: One day this should be reported as dead since 'z = x + y' is dead.
   int x = (y > 2); // no-warning
   ^{
     int z = x + y;
     // non-nested-warning@-1 {{Value stored to 'z' during its initialization is never read}}
     // non-nested-warning@-2 {{unused variable 'z'}}
     // non-nested-remark@-3 {{10-17: ''}}
   }();
 }

 void f24_B(int y) {
   // FIXME: One day this should be reported as dead since 'x' is just overwritten.
   __block int x = (y > 2); // no-warning
   ^{
     // FIXME: This should eventually be a dead store since it is never read either.
     x = 5; // no-warning
   }();
 }

 int f24_C(int y) {
   // FIXME: One day this should be reported as dead since 'x' is just overwritten.
   __block int x = (y > 2); // no-warning
   ^{
     x = 5; // no-warning
   }();
   return x;
 }

 int f24_D(int y) {
   __block int x = (y > 2); // no-warning
   ^{
     if (y > 4)
       x = 5; // no-warning
   }();
   return x;
 }

 // This example shows that writing to a variable captured by a block means that
 // it might not be dead.
 int f25(int y) {
   __block int x = (y > 2);
   __block int z = 0;
   void (^foo)() = ^{
     z = x + y;
   };
   x = 4; // no-warning
   foo();
   return z;
 }

 // This test is mostly the same as 'f25', but shows that the heuristic of
 // pruning out dead stores for variables that are just marked '__block' is
 // overly conservative.
 int f25_b(int y) {
   // FIXME: we should eventually report a dead store here.
   __block int x = (y > 2);
   __block int z = 0;
   x = 4; // no-warning
   return z;
 }

 int f26_nestedblocks() {
   int z;
   z = 1;
   __block int y = 0;
   ^{
     int k;
     k = 1; // non-nested-warning {{Value stored to 'k' is never read}}
     ^{
       y = z + 1;
     }();
   }();
   return y;
 }

 // The FOREACH macro in QT uses 'break' statements within statement expressions
 // placed within the increment code of for loops.
 void rdar8014335() {
   for (int i = 0 ; i != 10 ; ({ break; })) {
     for (;; ({ ++i; break; }))
       ;
     // non-nested-warning@-2 {{'break' is bound to current loop, GCC binds it to the enclosing loop}}
     // Note that the next value stored to 'i' is never executed
     // because the next statement to be executed is the 'break'
     // in the increment code of the first loop.
     i = i * 3; // non-nested-warning {{Value stored to 'i' is never read}}
   }
 }

 // <rdar://problem/8320674> NullStmts followed by do...while() can lead to disconnected CFG
 //
 // This previously caused bogus dead-stores warnings because the body of the first do...while was
 // disconnected from the entry of the function.
 typedef struct { float r; float i; } s_rdar8320674;
 typedef struct { s_rdar8320674 x[1]; } s2_rdar8320674;

 void rdar8320674(s_rdar8320674 *z, unsigned y, s2_rdar8320674 *st, int m)
 {
     s_rdar8320674 * z2;
     s_rdar8320674 * tw1 = st->x;
     s_rdar8320674 t;
     z2 = z + m;
     do{
         ; ;
         do{ (t).r = (*z2).r*(*tw1).r - (*z2).i*(*tw1).i; (t).i = (*z2).r*(*tw1).i + (*z2).i*(*tw1).r; }while(0);
         tw1 += y;
         do { (*z2).r=(*z).r-(t).r; (*z2).i=(*z).i-(t).i; }while(0);
         do { (*z).r += (t).r; (*z).i += (t).i; }while(0);
         ++z2;
         ++z;
     }while (--m);
 }

 // Avoid dead stores resulting from an assignment (and use) being unreachable.
 void rdar8405222_aux(int i);
 void rdar8405222() {
   const int show = 0;
   int i = 0;
   if (show)
     i = 5; // no-warning
   if (show)
     rdar8405222_aux(i);
 }

 // Look through chains of assignments, e.g.: int x = y = 0, when employing
 // silencing heuristics.
 int radar11185138_foo() {
   int x, y;
   x = y = 0; // non-nested-warning {{never read}}
   return y;
 }

 int rdar11185138_bar() {
   int y;
   int x = y = 0; // nested-warning {{Although the value stored}}
   x = 2;
   y = 2;
   return x + y;
 }

 int *radar11185138_baz() {
   int *x, *y;
   x = y = 0; // no-warning
   return y;
 }

 int getInt();
 int *getPtr();
 void testBOComma() {
   int x0 = (getInt(), 0); // non-nested-warning {{unused variable 'x0'}}
   int x1 = (getInt(), getInt());
   // non-nested-warning@-1 {{Value stored to 'x1' during its initialization is never read}}
   // non-nested-warning@-2 {{unused variable 'x1'}}

   int x2 = (getInt(), getInt(), getInt());
   // non-nested-warning@-1 {{Value stored to 'x2' during its initialization is never read}}
   // non-nested-warning@-2 {{unused variable 'x2'}}

   int x3;
   x3 = (getInt(), getInt(), 0);
   // non-nested-warning@-1 {{Value stored to 'x3' is never read}}

   int x4 = (getInt(), (getInt(), 0));
   // non-nested-warning@-1 {{unused variable 'x4'}}

   int y;
   int x5 = (getInt(), (y = 0));
   // non-nested-warning@-1 {{unused variable 'x5'}}
   // nested-warning@-2 {{Although the value stored}}

   int x6 = (getInt(), (y = getInt()));
   // non-nested-warning@-1 {{Value stored to 'x6' during its initialization is never read}}
   // non-nested-warning@-2 {{unused variable 'x6'}}
   // nested-warning@-3 {{Although the value stored}}

   int x7 = 0, x8 = getInt();
   // non-nested-warning@-1 {{Value stored to 'x8' during its initialization is never read}}
   // non-nested-warning@-2 {{unused variable 'x8'}}
   // non-nested-warning@-3 {{unused variable 'x7'}}

   int x9 = getInt(), x10 = 0;
   // non-nested-warning@-1 {{Value stored to 'x9' during its initialization is never read}}
   // non-nested-warning@-2 {{unused variable 'x9'}}
   // non-nested-warning@-3 {{unused variable 'x10'}}

   int m = getInt(), mm, mmm;
   // non-nested-warning@-1 {{Value stored to 'm' during its initialization is never read}}
   // non-nested-warning@-2 {{unused variable 'm'}}
   // non-nested-warning@-3 {{unused variable 'mm'}}
   // non-nested-warning@-4 {{unused variable 'mmm'}}

   int n, nn = getInt();
   // non-nested-warning@-1 {{Value stored to 'nn' during its initialization is never read}}
   // non-nested-warning@-2 {{unused variable 'n'}}
   // non-nested-warning@-3 {{unused variable 'nn'}}

   int *p;
   p = (getPtr(), (int *)0); // no warning
 }

 void testVolatile() {
   volatile int v;
   v = 0; // no warning
 }
	// RUN: %clang_analyze_cc1 -Wunused-variable -fblocks -Wno-unreachable-code \
	// RUN: -analyzer-checker=core,deadcode.DeadStores \
	// RUN: -analyzer-config deadcode.DeadStores:ShowFixIts=true \
	// RUN: -analyzer-config fixits-as-remarks=true \
	// RUN: -analyzer-config \
	// RUN: deadcode.DeadStores:WarnForDeadNestedAssignments=false \
	// RUN: -verify=non-nested %s

	// RUN: %clang_analyze_cc1 -Wunused-variable -fblocks -Wno-unreachable-code \
	// RUN: -analyzer-checker=core,deadcode.DeadStores \
	// RUN: -analyzer-config deadcode.DeadStores:ShowFixIts=true \
	// RUN: -analyzer-config fixits-as-remarks=true \
	// RUN: -verify=non-nested,nested %s

	void f1() {
	int k, y; // non-nested-warning {{unused variable 'k'}}
	// non-nested-warning@-1 {{unused variable 'y'}}
	int abc = 1;
	long idx = abc + 3 * 5; // non-nested-warning {{never read}}
	// non-nested-warning@-1 {{unused variable 'idx'}}
	// non-nested-remark@-2 {{11-24: ''}}
	}

	void f2(void *b) {
	char c = (char )b; // no-warning
	char *d = b + 1; // non-nested-warning {{never read}}
	// non-nested-warning@-1 {{unused variable 'd'}}
	// non-nested-remark@-2 {{10-17: ''}}
	printf("%s", c);
	// non-nested-warning@-1 {{implicitly declaring library function 'printf' with type 'int (const char *, ...)'}}
	// non-nested-note@-2 {{include the header <stdio.h> or explicitly provide a declaration for 'printf'}}
	}

	int f();
	void f3() {
	int r;
	if ((r = f()) != 0) { // no-warning
	int y = r; // no-warning
	printf("the error is: %d\n", y);
	}
	}

	void f4(int k) {
	k = 1;
	if (k)
	f1();
	k = 2; // non-nested-warning {{never read}}
	}

	void f5() {
	int x = 4; // no-warning
	int *p = &x; // non-nested-warning {{never read}}
	// non-nested-warning@-1 {{unused variable 'p'}}
	// non-nested-remark@-2 {{9-13: ''}}
	}

	int f6() {
	int x = 4;
	++x; // no-warning
	return 1;
	}

	int f7(int *p) {
	// This is allowed for defensive programming.
	p = 0; // no-warning
	return 1;
	}

	int f7b(int *p) {
	// This is allowed for defensive programming.
	p = (0); // no-warning
	return 1;
	}

	int f7c(int *p) {
	// This is allowed for defensive programming.
	p = (void *)0; // no-warning
	return 1;
	}

	int f7d(int *p) {
	// This is allowed for defensive programming.
	p = (void *)(0); // no-warning
	return 1;
	}

	// Warn for dead stores in nested expressions.
	int f8(int *p) {
	extern int *baz();
	if ((p = baz())) // nested-warning {{Although the value stored}}
	return 1;
	return 0;
	}

	int f9() {
	int x = 4;
	x = x + 10; // non-nested-warning {{never read}}
	return 1;
	}

	int f10() {
	int x = 4;
	x = 10 + x; // non-nested-warning {{never read}}
	return 1;
	}

	int f11() {
	int x = 4;
	return x++; // non-nested-warning {{never read}}
	}

	int f11b() {
	int x = 4;
	return ((((++x)))); // no-warning
	}

	int f12a(int y) {
	int x = y; // non-nested-warning {{unused variable 'x'}}
	return 1;
	}

	int f12b(int y) {
	int x __attribute__((unused)) = y; // no-warning
	return 1;
	}

	int f12c(int y) {
	// Allow initialiation of scalar variables by parameters as a form of
	// defensive programming.
	int x = y; // no-warning
	x = 1;
	return x;
	}

	// Filed with PR 2630. This code should produce no warnings.
	int f13(void) {
	int a = 1;
	int b, c = b = a + a;

	if (b > 0)
	return (0);
	return (a + b + c);
	}

	// Filed with PR 2763.
	int f14(int count) {
	int index, nextLineIndex;
	for (index = 0; index < count; index = nextLineIndex + 1) {
	nextLineIndex = index + 1; // no-warning
	continue;
	}
	return index;
	}

	// Test case for <rdar://problem/6248086>
	void f15(unsigned x, unsigned y) {
	int count = x * y; // no-warning
	int z[count]; // non-nested-warning {{unused variable 'z'}}
	}

	// Warn for dead stores in nested expressions.
	int f16(int x) {
	x = x * 2;
	x = sizeof(int[x = (x \|\| x + 1) * 2]) ? 5 : 8;
	// nested-warning@-1 {{Although the value stored}}
	return x;
	}

	// Self-assignments should not be flagged as dead stores.
	void f17() {
	int x = 1;
	x = x;
	}

	// <rdar://problem/6506065>
	// The values of dead stores are only "consumed" in an enclosing expression
	// what that value is actually used. In other words, don't say "Although the
	// value stored to 'x' is used...".
	int f18() {
	int x = 0; // no-warning
	if (1)
	x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
	while (1)
	x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
	// unreachable.
	do
	x = 10; // no-warning
	while (1);
	return (x = 10); // no-warning
	}

	int f18_a() {
	int x = 0; // no-warning
	return (x = 10); // nested-warning {{Although the value stored}}
	}

	void f18_b() {
	int x = 0; // no-warning
	if (1)
	x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
	}

	void f18_c() {
	int x = 0;
	while (1)
	x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
	}

	void f18_d() {
	int x = 0; // no-warning
	do
	x = 10; // non-nested-warning {{Value stored to 'x' is never read}}
	while (1);
	}

	// PR 3514: false positive `dead initialization` warning for init to global
	// http://llvm.org/bugs/show_bug.cgi?id=3514
	extern const int MyConstant;
	int f19(void) {
	int x = MyConstant; // no-warning
	x = 1;
	return x;
	}

	int f19b(void) { // This case is the same as f19.
	const int MyConstant = 0;
	int x = MyConstant; // no-warning
	x = 1;
	return x;
	}

	void f20(void) {
	int x = 1; // no-warning
	#pragma unused(x)
	}

	void halt() __attribute__((noreturn));
	int f21() {
	int x = 4;
	x = x + 1; // non-nested-warning {{never read}}
	if (1) {
	halt();
	(void)x;
	}
	return 1;
	}

	int j;
	void f22() {
	int x = 4;
	int y1 = 4;
	int y2 = 4;
	int y3 = 4;
	int y4 = 4;
	int y5 = 4;
	int y6 = 4;
	int y7 = 4;
	int y8 = 4;
	int y9 = 4;
	int y10 = 4;
	int y11 = 4;
	int y12 = 4;
	int y13 = 4;
	int y14 = 4;
	int y15 = 4;
	int y16 = 4;
	int y17 = 4;
	int y18 = 4;
	int y19 = 4;
	int y20 = 4;

	x = x + 1; // non-nested-warning {{never read}}
	++y1;
	++y2;
	++y3;
	++y4;
	++y5;
	++y6;
	++y7;
	++y8;
	++y9;
	++y10;
	++y11;
	++y12;
	++y13;
	++y14;
	++y15;
	++y16;
	++y17;
	++y18;
	++y19;
	++y20;

	switch (j) {
	case 1:
	if (0)
	(void)x;
	if (1) {
	(void)y1;
	return;
	}
	(void)x;
	break;
	case 2:
	if (0)
	(void)x;
	else {
	(void)y2;
	return;
	}
	(void)x;
	break;
	case 3:
	if (1) {
	(void)y3;
	return;
	} else
	(void)x;
	(void)x;
	break;
	case 4:
	0 ?: ((void)y4, ({ return; }));
	(void)x;
	break;
	case 5:
	1 ?: (void)x;
	0 ? (void)x : ((void)y5, ({ return; }));
	(void)x;
	break;
	case 6:
	1 ? ((void)y6, ({ return; })) : (void)x;
	(void)x;
	break;
	case 7:
	(void)(0 && x);
	(void)y7;
	(void)(0 \|\| (y8, ({ return; }), 1));
	// non-nested-warning@-1 {{expression result unused}}
	(void)x;
	break;
	case 8:
	(void)(1 && (y9, ({ return; }), 1));
	// non-nested-warning@-1 {{expression result unused}}
	(void)x;
	break;
	case 9:
	(void)(1 \|\| x);
	(void)y10;
	break;
	case 10:
	while (0) {
	(void)x;
	}
	(void)y11;
	break;
	case 11:
	while (1) {
	(void)y12;
	}
	(void)x;
	break;
	case 12:
	do {
	(void)y13;
	} while (0);
	(void)y14;
	break;
	case 13:
	do {
	(void)y15;
	} while (1);
	(void)x;
	break;
	case 14:
	for (;;) {
	(void)y16;
	}
	(void)x;
	break;
	case 15:
	for (; 1;) {
	(void)y17;
	}
	(void)x;
	break;
	case 16:
	for (; 0;) {
	(void)x;
	}
	(void)y18;
	break;
	case 17:
	__builtin_choose_expr(0, (void)x, ((void)y19, ({ return; })));
	(void)x;
	break;
	case 19:
	__builtin_choose_expr(1, ((void)y20, ({ return; })), (void)x);
	(void)x;
	break;
	}
	}

	void f23_aux(const char *s);
	void f23(int argc, char **argv) {
	int shouldLog = (argc > 1); // no-warning
	^{
	if (shouldLog)
	f23_aux("I did too use it!\n");
	else
	f23_aux("I shouldn't log. Wait.. d'oh!\n");
	}();
	}

	void f23_pos(int argc, char **argv) {
	int shouldLog = (argc > 1);
	// non-nested-warning@-1 {{Value stored to 'shouldLog' during its initialization is never read}}
	// non-nested-warning@-2 {{unused variable 'shouldLog'}}
	// non-nested-remark@-3 {{16-28: ''}}
	^{
	f23_aux("I did too use it!\n");
	}();
	}

	void f24_A(int y) {
	// FIXME: One day this should be reported as dead since 'z = x + y' is dead.
	int x = (y > 2); // no-warning
	^{
	int z = x + y;
	// non-nested-warning@-1 {{Value stored to 'z' during its initialization is never read}}
	// non-nested-warning@-2 {{unused variable 'z'}}
	// non-nested-remark@-3 {{10-17: ''}}
	}();
	}

	void f24_B(int y) {
	// FIXME: One day this should be reported as dead since 'x' is just overwritten.
	__block int x = (y > 2); // no-warning
	^{
	// FIXME: This should eventually be a dead store since it is never read either.
	x = 5; // no-warning
	}();
	}

	int f24_C(int y) {
	// FIXME: One day this should be reported as dead since 'x' is just overwritten.
	__block int x = (y > 2); // no-warning
	^{
	x = 5; // no-warning
	}();
	return x;
	}

	int f24_D(int y) {
	__block int x = (y > 2); // no-warning
	^{
	if (y > 4)
	x = 5; // no-warning
	}();
	return x;
	}

	// This example shows that writing to a variable captured by a block means that
	// it might not be dead.
	int f25(int y) {
	__block int x = (y > 2);
	__block int z = 0;
	void (^foo)() = ^{
	z = x + y;
	};
	x = 4; // no-warning
	foo();
	return z;
	}

	// This test is mostly the same as 'f25', but shows that the heuristic of
	// pruning out dead stores for variables that are just marked '__block' is
	// overly conservative.
	int f25_b(int y) {
	// FIXME: we should eventually report a dead store here.
	__block int x = (y > 2);
	__block int z = 0;
	x = 4; // no-warning
	return z;
	}

	int f26_nestedblocks() {
	int z;
	z = 1;
	__block int y = 0;
	^{
	int k;
	k = 1; // non-nested-warning {{Value stored to 'k' is never read}}
	^{
	y = z + 1;
	}();
	}();
	return y;
	}

	// The FOREACH macro in QT uses 'break' statements within statement expressions
	// placed within the increment code of for loops.
	void rdar8014335() {
	for (int i = 0 ; i != 10 ; ({ break; })) {
	for (;; ({ ++i; break; }))
	;
	// non-nested-warning@-2 {{'break' is bound to current loop, GCC binds it to the enclosing loop}}
	// Note that the next value stored to 'i' is never executed
	// because the next statement to be executed is the 'break'
	// in the increment code of the first loop.
	i = i * 3; // non-nested-warning {{Value stored to 'i' is never read}}
	}
	}

	// <rdar://problem/8320674> NullStmts followed by do...while() can lead to disconnected CFG
	//
	// This previously caused bogus dead-stores warnings because the body of the first do...while was
	// disconnected from the entry of the function.
	typedef struct { float r; float i; } s_rdar8320674;
	typedef struct { s_rdar8320674 x[1]; } s2_rdar8320674;

	void rdar8320674(s_rdar8320674 z, unsigned y, s2_rdar8320674 st, int m)
	{
	s_rdar8320674 * z2;
	s_rdar8320674 * tw1 = st->x;
	s_rdar8320674 t;
	z2 = z + m;
	do{
	; ;
	do{ (t).r = (z2).r(tw1).r - (z2).i(tw1).i; (t).i = (z2).r(tw1).i + (z2).i(tw1).r; }while(0);
	tw1 += y;
	do { (z2).r=(z).r-(t).r; (z2).i=(z).i-(t).i; }while(0);
	do { (z).r += (t).r; (z).i += (t).i; }while(0);
	++z2;
	++z;
	}while (--m);
	}

	// Avoid dead stores resulting from an assignment (and use) being unreachable.
	void rdar8405222_aux(int i);
	void rdar8405222() {
	const int show = 0;
	int i = 0;
	if (show)
	i = 5; // no-warning
	if (show)
	rdar8405222_aux(i);
	}

	// Look through chains of assignments, e.g.: int x = y = 0, when employing
	// silencing heuristics.
	int radar11185138_foo() {
	int x, y;
	x = y = 0; // non-nested-warning {{never read}}
	return y;
	}

	int rdar11185138_bar() {
	int y;
	int x = y = 0; // nested-warning {{Although the value stored}}
	x = 2;
	y = 2;
	return x + y;
	}

	int *radar11185138_baz() {
	int x, y;
	x = y = 0; // no-warning
	return y;
	}

	int getInt();
	int *getPtr();
	void testBOComma() {
	int x0 = (getInt(), 0); // non-nested-warning {{unused variable 'x0'}}
	int x1 = (getInt(), getInt());
	// non-nested-warning@-1 {{Value stored to 'x1' during its initialization is never read}}
	// non-nested-warning@-2 {{unused variable 'x1'}}

	int x2 = (getInt(), getInt(), getInt());
	// non-nested-warning@-1 {{Value stored to 'x2' during its initialization is never read}}
	// non-nested-warning@-2 {{unused variable 'x2'}}

	int x3;
	x3 = (getInt(), getInt(), 0);
	// non-nested-warning@-1 {{Value stored to 'x3' is never read}}

	int x4 = (getInt(), (getInt(), 0));
	// non-nested-warning@-1 {{unused variable 'x4'}}

	int y;
	int x5 = (getInt(), (y = 0));
	// non-nested-warning@-1 {{unused variable 'x5'}}
	// nested-warning@-2 {{Although the value stored}}

	int x6 = (getInt(), (y = getInt()));
	// non-nested-warning@-1 {{Value stored to 'x6' during its initialization is never read}}
	// non-nested-warning@-2 {{unused variable 'x6'}}
	// nested-warning@-3 {{Although the value stored}}

	int x7 = 0, x8 = getInt();
	// non-nested-warning@-1 {{Value stored to 'x8' during its initialization is never read}}
	// non-nested-warning@-2 {{unused variable 'x8'}}
	// non-nested-warning@-3 {{unused variable 'x7'}}

	int x9 = getInt(), x10 = 0;
	// non-nested-warning@-1 {{Value stored to 'x9' during its initialization is never read}}
	// non-nested-warning@-2 {{unused variable 'x9'}}
	// non-nested-warning@-3 {{unused variable 'x10'}}

	int m = getInt(), mm, mmm;
	// non-nested-warning@-1 {{Value stored to 'm' during its initialization is never read}}
	// non-nested-warning@-2 {{unused variable 'm'}}
	// non-nested-warning@-3 {{unused variable 'mm'}}
	// non-nested-warning@-4 {{unused variable 'mmm'}}

	int n, nn = getInt();
	// non-nested-warning@-1 {{Value stored to 'nn' during its initialization is never read}}
	// non-nested-warning@-2 {{unused variable 'n'}}
	// non-nested-warning@-3 {{unused variable 'nn'}}

	int *p;
	p = (getPtr(), (int *)0); // no warning
	}

	void testVolatile() {
	volatile int v;
	v = 0; // no warning
	}