Add some automatic tests for DivideZero checker

[ztamas]

Based on CODE_OWNERS.txt.

test/Analysis/div-zero.cpp

 // RUN: %clang_analyze_cc1 -analyzer-checker=core.DivideZero -verify %s
 
 int fooPR10616 (int qX ) {
   int a, c, d;
 
   d = (qX-1);
   while ( d != 0 ) {
     d = c - (c/d) * d;
   }
 
   return (a % (qX-1)); // expected-warning {{Division by zero}}
 
 }
+
+
+void testDiv1() {
+  (void)(42 / 0);
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testDiv2() {
+  (void)(42 / false);
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testDiv3() {
+  (void)(42 / !1);
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testDiv4() {
+  (void)(42 / (1 - 1));
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testDiv5() {
+  (void)(42 / !(1 + 1));
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testDiv6a() {
+  (void)(42 / (int)0.0);
+  // expected-warning@-1 {{division by zero is undefined}}
+  // Missing Division by zero warning
+}
+
+
+void testDiv6b() {
+  int x = (int)0.0;
+  (void)(42 / x);
+  // Missing Division by zero warning
+}
+
+
+void testDiv6c() {
+  float y = 0.2;
+  float z = 0.1;
+  int x = (int)(z + y);
+  (void)(42 / x);
+  // Missing Division by zero warning
+}
+
+
+void testDiv7() {
+  (void)(true / 0);
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testDiv8() {
+  (void)(!1 / 0);
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testDiv9() {
+  (void)((int)(9.0) / 0);
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testDiv10() {
+  (void)((10 - 1) / 0);
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testRem() {
+  (void)(42 % 0);
+  // expected-warning@-1 {{remainder by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+int testDivAssign(int x) {
+  return (x /= 0);
+  // expected-warning@-1 {{division by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+int testRemAssign(int x) {
+  return (x %= 0);
+  // expected-warning@-1 {{remainder by zero is undefined}}
+  // expected-warning@-2 {{Division by zero}}
+}
+
+
+void testFloatDiv() {
+  (void)(42.0 / 0);
+  // No warning, the checker handles scalar types only
+}
+
+
+void testDivPath() {
+  int x = 2;
+  int y = 2;
+  int z = 10;
+
+  x = y / z;
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testDivPath2() {
+  int x = 2;
+  int y = 0;
+  int z = 10;
+
+  x = y / z;
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testRemPath() {
+  int x = 2;
+  int y = 2;
+  int z = 10;
+
+  x = z % y;
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testRemPath2() {
+  int x = 2;
+  int y = 2;
+  int z = 0;
+
+  x = z % y;
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testAdditionPath() {
+  int x = 2;
+  int y = 2;
+  int z = -2;
+
+  x = z + y;
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testSubtractionPath() {
+  int x = 2;
+  int y = 2;
+  int z = 2;
+
+  x = z - y;
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testNegationPath() {
+  int x = 2;
+  int y = 2;
+  int z = 2;
+
+  x = - y;
+  x = x + z;
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testIfThenPath() {
+  int x = 2;
+  int y = 2;
+  int z = 2;
+
+  if(y > 0)
+    x = z - y;
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testIfElsePath() {
+  int x = 2;
+  int y = 2;
+  int z = 2;
+
+  if(y < 0) {
+    x = z - y + 1;
+  } else {
+    x = z - y;
+  }
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testSwitchPath() {
+  int x = 2;
+  int y = 2;
+  int z = 2;
+
+  switch(y) {
+    case 1: x = y; break;
+    case 3: x = z; break;
+    default: x %= z; break;
+  }
+
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testForLoopPath1() {
+  int x = 5;
+
+  for(int i = 0; i < 5; ++i) {
+    x = x - 1;
+  }
+  (void)(42 / x); // Missing warning
+}
+
+
+void testForLoopPath2() {
+  int x = 0;
+
+  for(int i = 0; i < 5; ++i) {}
+  (void)(42 / x); // Missing warning
+}
+
+
+void testForLoopPath3() {
+  int x = 0;
+
+  for(int i = 0; i < 1; ++i) {}
+
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+void testWhileLoopPath() {
+  int x = 0;
+
+  int i = 0;
+  while(i < 5) {
+    ++i;
+  }
+  (void)(42 / x); // Missing warning
+}
+
+
+void testWhileLoopPath2() {
+  int x = 0;
+
+  int i = 0;
+  do {
+    ++i;
+  } while(i < 5);
+  (void)(42 / x); // Missing warning
+}
+
+
+void testWhileLoopPath3() {
+  int x = 0;
+
+  int i = 0;
+  while(i < 1) {
+    ++i;
+  }
+  (void)(42 / x); // expected-warning {{Division by zero}}
+}
+
+
+class BigInt {
+};
+
+BigInt operator/(const BigInt& x, int y) {
+  (void)(10 / y); // expected-warning {{Division by zero}}
+  return x;
+}
+
+BigInt testOverwrittenOperator(BigInt x) {
+  return x / 0; // no warning
+}
+