[clang-tools-extra] [clang-tidy] warn when `true` is used as a preprocessor keyword in C (PR #128265)

[Piotr Zegar via cfe-commits]

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@@ -0,0 +1,45 @@
+// RUN: %check_clang_tidy -std=c99 %s bugprone-true-macro %t
+// RUN: %check_clang_tidy -std=c11 %s bugprone-true-macro %t
+// RUN: %check_clang_tidy -std=c17 %s bugprone-true-macro %t
+
+#define FOO true
+// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: in C 'true' is treated as an undefined macro and evaluates to a falsy value; consider replacing it with '1' [bugprone-true-macro]
+// CHECK-FIXES: 1
+
+#if true
+// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: in C 'true' is treated as an undefined macro and evaluates to a falsy value; consider replacing it with '1' [bugprone-true-macro]
+// CHECK-FIXES: 1
+#endif
+
+#if false || true
+// CHECK-MESSAGES: :[[@LINE-1]]:2: warning: in C 'true' in the condition is treated as an undefined macro and evaluates to a falsy value; consider replacing it with '1' [bugprone-true-macro]
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PiotrZSL wrote:

maybe instead falsy, just write 'false'

https://github.com/llvm/llvm-project/pull/128265