[clang] [clang-tools-extra] [clang-tidy] Warn about misuse of sizeof operator in loops. (PR #143205)

[Malavika Samak via cfe-commits]

================
@@ -164,6 +164,53 @@ int Test2(MyConstChar* A) {
   return sum;
 }
 
+struct A {
+   int array[10];
+};
+
+struct B {
+  struct A a;
+};
+
+void loop_access_elements(int num, struct B b) {
+    struct A arr[10];
+    char buf[20];
+
+    // CHECK-MESSAGES: :[[@LINE+1]]:5: warning: suspicious usage of 'sizeof' in the loop [bugprone-sizeof-expression]
+    for(int i = 0; i < sizeof(arr); i++) {
+       struct A a = arr[i];
+    }
+
+    // Loop warning should not trigger here, even though this code is incorrect
+    // CHECK-MESSAGES: :[[@LINE+2]]:24: warning: suspicious usage of 'sizeof(K)'; did you mean 'K'? [bugprone-sizeof-expression]
+    // CHECK-MESSAGES: :[[@LINE+1]]:34: warning: suspicious usage of 'sizeof(...)/sizeof(...)'; numerator is not a multiple of denominator [bugprone-sizeof-expression] 
+    for(int i = 0; i < sizeof(10)/sizeof(A); i++) {
+       struct A a = arr[i];
+    }
+    
+    // Should not warn here
+    for(int i = 0; i < sizeof(arr)/sizeof(A); i++) {}
+
+    // CHECK-MESSAGES: :[[@LINE+1]]:5: warning: suspicious usage of 'sizeof' in the loop [bugprone-sizeof-expression]
+    for(int j = 0; j < sizeof(b.a.array); j++) {}
+  
+    // Should not warn here
+    for(int i = 0; i < sizeof(buf); i++) {} 
+  
+    int i = 0;
+    // CHECK-MESSAGES: :[[@LINE+1]]:5: warning: suspicious usage of 'sizeof' in the loop [bugprone-sizeof-expression]
+    while(i <= sizeof(arr)) {i++;}
+   
+    i = 0;
+    do {
+     i++;
+    } while(i <= sizeof(arr));
----------------
malavikasamak wrote:

Done.

https://github.com/llvm/llvm-project/pull/143205