[PATCH] D29857: Catch trivially true statements of the form a != 1 || a != 3. Statements likethese are likely errors. They are particularly easy to miss when handling enums:enum State {RUNNING, STOPPED, STARTING, ENDING}...if (state != RUNNING || state !=...

[Blaise Watson via Phabricator via cfe-commits]

watsond updated this revision to Diff 88072.
watsond added a comment.



Updating D29857: Catch trivially true statements of the form a != 1 || a != 3. Statements like
==============================================================================================

these are likely errors. They are particularly easy to miss when handling enums:

enum State {
RUNNING,
STOPPED,
STARTING,
ENDING
}

...
if (state != RUNNING || state !=...


https://reviews.llvm.org/D29857

Files:
  clang-tidy/misc/RedundantExpressionCheck.cpp
  test/clang-tidy/misc-redundant-expression.cpp


Index: test/clang-tidy/misc-redundant-expression.cpp
===================================================================
--- test/clang-tidy/misc-redundant-expression.cpp
+++ test/clang-tidy/misc-redundant-expression.cpp
@@ -321,6 +321,8 @@
   // CHECK-MESSAGES: :[[@LINE-1]]:15: warning: logical expression is always true
   if (X <= 10 || X >= 11) return 1;
   // CHECK-MESSAGES: :[[@LINE-1]]:15: warning: logical expression is always true
+  if (X != 7 || X != 14) return 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: logical expression is always true
 
   if (X < 7 && X < 6) return 1;
   // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: expression is redundant
Index: clang-tidy/misc/RedundantExpressionCheck.cpp
===================================================================
--- clang-tidy/misc/RedundantExpressionCheck.cpp
+++ clang-tidy/misc/RedundantExpressionCheck.cpp
@@ -239,6 +239,11 @@
       (OpcodeRHS == BO_LT || OpcodeRHS == BO_LE))
     return true;
 
+  // Handle cases where constants are different but both ops are !=, like:
+  // x != 5 || x != 10
+  if (OpcodeLHS == BO_NE || OpcodeLHS == BO_NE)
+    return true;
+
   return false;
 }
 


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