[Static Analyzer] Warn when inner and outer conditions are identical. The inner condition is always true.

Reviewed in http://reviews.llvm.org/D10892.

llvm-svn: 244435

clang/lib/StaticAnalyzer/Checkers/IdenticalExprChecker.cpp

@@ -108,6 +108,24 @@ bool FindIdenticalExprVisitor::VisitIfStmt(const IfStmt *I) {
   const Stmt *Stmt1 = I->getThen();
   const Stmt *Stmt2 = I->getElse();
 
+  // Check for identical inner condition:
+  //
+  // if (x<10) {
+  //   if (x<10) {
+  //   ..
+  if (const CompoundStmt *CS = dyn_cast<CompoundStmt>(Stmt1)) {
+    if (!CS->body_empty()) {
+      const IfStmt *InnerIf = dyn_cast<IfStmt>(*CS->body_begin());
+      if (InnerIf && isIdenticalStmt(AC->getASTContext(), I->getCond(), InnerIf->getCond(), /*ignoreSideEffects=*/ false)) {
+        PathDiagnosticLocation ELoc(InnerIf->getCond(), BR.getSourceManager(), AC);
+        BR.EmitBasicReport(AC->getDecl(), Checker, "Identical conditions",
+          categories::LogicError,
+          "conditions of the inner and outer statements are identical",
+          ELoc);
+      }
+    }
+  }
+
   // Check for identical conditions:
   //
   // if (b) {

clang/test/Analysis/identical-expressions.cpp

@@ -1530,3 +1530,35 @@ void test_nowarn_long() {
     c = 0LL;
   }
 }
+
+// Identical inner conditions
+
+void test_warn_inner_if_1(int x) {
+  if (x == 1) {
+    if (x == 1) // expected-warning {{conditions of the inner and outer statements are identical}}
+      ;
+  }
+
+  // FIXME: Should warn here. The warning is currently not emitted because there
+  // is code between the conditions.
+  if (x == 1) {
+    int y = x;
+    if (x == 1)
+      ;
+  }
+}
+
+void test_nowarn_inner_if_1(int x) {
+  // Don't warn when condition has side effects.
+  if (x++ == 1) {
+    if (x++ == 1)
+      ;
+  }
+
+  // Don't warn when x is changed before inner condition.
+  if (x < 10) {
+    x++;
+    if (x < 10)
+      ;
+  }
+}