Extend -Wtautological-overlap-compare to more cases.

Previously, -Wtautological-overlap-compare did not warn on cases where the
boolean expression was in an assignment or return statement.  This patch
should cause all boolean statements to be passed to the tautological compare
checks in the CFG analysis.

This is one of the issues from PR13101

llvm-svn: 290920

2 files changed, 52 insertions, 3 deletions

diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index bf3cc05cdb6..a1a463f1d03 100644
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -1690,15 +1690,19 @@ CFGBuilder::VisitLogicalOperator(BinaryOperator *B,
     // we have been provided.
     ExitBlock = RHSBlock = createBlock(false);
 
+    // Even though KnownVal is only used in the else branch of the next
+    // conditional, tryEvaluateBool performs additional checking on the
+    // Expr, so it should be called unconditionally.
+    TryResult KnownVal = tryEvaluateBool(RHS);
+    if (!KnownVal.isKnown())
+      KnownVal = tryEvaluateBool(B);
+
     if (!Term) {
       assert(TrueBlock == FalseBlock);
       addSuccessor(RHSBlock, TrueBlock);
     }
     else {
       RHSBlock->setTerminator(Term);
-      TryResult KnownVal = tryEvaluateBool(RHS);
-      if (!KnownVal.isKnown())
-        KnownVal = tryEvaluateBool(B);
       addSuccessor(RHSBlock, TrueBlock, !KnownVal.isFalse());
       addSuccessor(RHSBlock, FalseBlock, !KnownVal.isTrue());
     }
diff --git a/clang/test/Sema/warn-overlap.c b/clang/test/Sema/warn-overlap.c
index 1e8a614d0ff..6299c511fe2 100644
--- a/clang/test/Sema/warn-overlap.c
+++ b/clang/test/Sema/warn-overlap.c
@@ -96,3 +96,48 @@ void array_out_of_bounds() {
   int buffer[4];
   x = (-7 > 0) ? (buffer[-7]) : 0;
 }
+
+void bool_contexts(int x) {
+  if (x > 4 || x < 10) {}
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+  for (;x > 4 || x < 10;) {}
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+  while (x > 4 || x < 10) {}
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+  do {} while (x > 4 || x < 10);
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+  x = (x > 4 || x < 10) ? 1 : 2;
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+  if ((void)5, x > 4 || x < 10) {}
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+}
+
+void assignment(int x) {
+  int a = x > 4 || x < 10;
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+  int b = x < 2 && x > 5;
+  // expected-warning@-1{{overlapping comparisons always evaluate to false}}
+
+  int c = x != 1 || x != 3;
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+  int d = x == 1 && x == 2;
+  // expected-warning@-1{{overlapping comparisons always evaluate to false}}
+
+  int e = x < 1 || x != 0;
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+}
+
+int returns(int x) {
+  return x > 4 || x < 10;
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+  return x < 2 && x > 5;
+  // expected-warning@-1{{overlapping comparisons always evaluate to false}}
+
+  return x != 1 || x != 3;
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+  return x == 1 && x == 2;
+  // expected-warning@-1{{overlapping comparisons always evaluate to false}}
+
+  return x < 1 || x != 0;
+  // expected-warning@-1{{overlapping comparisons always evaluate to true}}
+}