From a4f43fc2ad446810afe62472db829b447bf56e64 Mon Sep 17 00:00:00 2001
From: Paul Fultz II <pfultz2@yahoo.com>
Date: Mon, 7 Sep 2020 00:53:41 -0500
Subject: [PATCH] Fix issue 8234: false negative: (warning) Opposite inner 'if'
 condition leads to a dead code block. (#2781)

---
 lib/astutils.cpp       | 11 +++++++++++
 lib/checkcondition.cpp |  6 ++++--
 lib/token.h            | 20 ++++++++++++++++++++
 test/testcondition.cpp |  6 ++++++
 test/testother.cpp     |  2 +-
 5 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/lib/astutils.cpp b/lib/astutils.cpp
index 06728799e..791c5f20d 100644
--- a/lib/astutils.cpp
+++ b/lib/astutils.cpp
@@ -956,6 +956,17 @@ bool isOppositeCond(bool isNot, bool cpp, const Token * const cond1, const Token
     if (!cond1 || !cond2)
         return false;
 
+    if (cond1->str() == "&&" && cond2->str() == "&&") {
+        for(const Token* tok1:{cond1->astOperand1(), cond1->astOperand2()}) {
+            for(const Token* tok2:{cond2->astOperand1(), cond2->astOperand2()}) {
+                if (isSameExpression(cpp, true, tok1, tok2, library, pure, followVar, errors)) {
+                    if (isOppositeCond(isNot, cpp, tok1->astSibling(), tok2->astSibling(), library, pure, followVar, errors))
+                        return true;
+                }
+            }
+        }
+    }
+
     if (cond1->str() == "!") {
         if (cond2->str() == "!=") {
             if (cond2->astOperand1() && cond2->astOperand1()->str() == "0")
diff --git a/lib/checkcondition.cpp b/lib/checkcondition.cpp
index 29312c071..5badfec1e 100644
--- a/lib/checkcondition.cpp
+++ b/lib/checkcondition.cpp
@@ -701,8 +701,10 @@ void CheckCondition::multiCondition2()
                             if (!firstCondition)
                                 return ChildrenToVisit::none;
                             if (firstCondition->str() == "&&") {
-                                return ChildrenToVisit::op1_and_op2;
-                            } else if (!firstCondition->hasKnownIntValue()) {
+                                if (!isOppositeCond(false, mTokenizer->isCPP(), firstCondition, cond2, mSettings->library, true, true))
+                                    return ChildrenToVisit::op1_and_op2;
+                            }
+                            if (!firstCondition->hasKnownIntValue()) {
                                 if (!isReturnVar && isOppositeCond(false, mTokenizer->isCPP(), firstCondition, cond2, mSettings->library, true, true, &errorPath)) {
                                     if (!isAliased(vars))
                                         oppositeInnerConditionError(firstCondition, cond2, errorPath);
diff --git a/lib/token.h b/lib/token.h
index ca44a70b1..df41a5d89 100644
--- a/lib/token.h
+++ b/lib/token.h
@@ -1263,6 +1263,26 @@ public:
     const Token * astParent() const {
         return mImpl->mAstParent;
     }
+    Token * astSibling() {
+        if (!astParent())
+            return nullptr;
+        if (this == astParent()->astOperand1())
+            return astParent()->astOperand2();
+        else if (this == astParent()->astOperand2())
+            return astParent()->astOperand1();
+        return nullptr;
+        
+    }
+    const Token * astSibling() const {
+        if (!astParent())
+            return nullptr;
+        if (this == astParent()->astOperand1())
+            return astParent()->astOperand2();
+        else if (this == astParent()->astOperand2())
+            return astParent()->astOperand1();
+        return nullptr;
+        
+    }
     Token *astTop() {
         Token *ret = this;
         while (ret->mImpl->mAstParent)
diff --git a/test/testcondition.cpp b/test/testcondition.cpp
index 4f7fb5d24..823947033 100644
--- a/test/testcondition.cpp
+++ b/test/testcondition.cpp
@@ -2310,6 +2310,12 @@ private:
               "  }"
               "}");
         ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:3]: (warning) Opposite inner 'if' condition leads to a dead code block.\n", errout.str());
+
+        check("void f(bool x, const int a, const int b) {\n"
+              "        if(x && a < b)\n"
+              "            if( x && a > b){}\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:3]: (warning) Opposite inner 'if' condition leads to a dead code block.\n", errout.str());
     }
 
     void oppositeInnerConditionEmpty() {
diff --git a/test/testother.cpp b/test/testother.cpp
index 22b5f7c76..99f688320 100644
--- a/test/testother.cpp
+++ b/test/testother.cpp
@@ -5310,7 +5310,7 @@ private:
         check("void f(int* x, bool b) {\n"
               "    if ((!x && b) || (x != 0 && b)) {}\n"
               "}\n");
-        ASSERT_EQUALS("", errout.str());
+        ASSERT_EQUALS("[test.cpp:2]: (style) Opposite expression on both sides of '||'.\n", errout.str());
     }
 
     void oppositeExpression() {