dead-stores.c

// RUN: clang -analyze -warn-dead-stores -verify %s &&
// RUN: clang -analyze -checker-simple -analyzer-store=basic -analyzer-constraints=basic -warn-dead-stores -verify %s &&
// RUN: clang -analyze -checker-simple -analyzer-store=basic -analyzer-constraints=range -warn-dead-stores -verify %s &&
// RUN: clang -analyze -checker-cfref -analyzer-store=basic -analyzer-constraints=basic -warn-dead-stores -verify %s &&
// RUN: clang -analyze -checker-cfref -analyzer-store=basic -analyzer-constraints=range -warn-dead-stores -verify %s &&
// RUN: clang -analyze -checker-cfref -analyzer-store=region -analyzer-constraints=basic -warn-dead-stores -verify %s &&
// RUN: clang -analyze -checker-cfref -analyzer-store=region -analyzer-constraints=range -warn-dead-stores -verify %s

void f1() {
  int k, y;
  int abc=1;
  long idx=abc+3*5; // expected-warning {{never read}}
}

void f2(void *b) {
 char *c = (char*)b; // no-warning
 char *d = b+1; // expected-warning {{never read}}
 printf("%s", c); // expected-warning{{implicitly declaring C library function 'printf' with type 'int (char const *, ...)'}} \
 // expected-note{{please include the header <stdio.h> or explicitly provide a declaration for 'printf'}}
}

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;  // expected-warning {{never read}}
}

void f5() {

  int x = 4; // no-warning
  int *p = &x; // expected-warning{{never read}}

}

int f6() {
  
  int x = 4;
  ++x; // expected-warning{{never read}}
  return 1;
}

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

int f8(int *p) {
  extern int *baz();
  if (p = baz()) // expected-warning{{Although the value}}
    return 1;
  return 0;
}

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

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

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

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

int f12a(int y) {
  int x = y;  // expected-warning{{never read}}
  return 1;
}
int f12b(int y) {
  int x __attribute__((unused)) = y;  // no-warning
  return 1;
}

// 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];
}

int f16(int x) {
  x = x * 2;
  x = sizeof(int [x = (x || x + 1) * 2]) // expected-warning{{Although the value stored to 'x' is used}}
      ? 5 : 8;
  return x;
}

// Self-assignments should not be flagged as dead stores.
int f17() {
  int x = 1;
  x = x; // no-warning
}

// <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;  // expected-warning{{Value stored to 'x' is never read}}
   while (1)
      x = 10;  // expected-warning{{Value stored to 'x' is never read}}
   do
      x = 10;   // expected-warning{{Value stored to 'x' is never read}}
   while (1);

   return (x = 10); // expected-warning{{Although the value stored to 'x' is used in the enclosing expression, the value is never actually read from 'x'}}
}

// 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) { // FIXME: Should this case be considered the same as f19?
  const int MyConstant = 0;
  int x = MyConstant; // expected-warning{{never read}}
  x = 1;
  return x;  
}

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