From a42976d656bc61eff72765a4cfab3fc1668f6f39 Mon Sep 17 00:00:00 2001
From: Paul Fultz II <pfultz2@yahoo.com>
Date: Mon, 14 Sep 2020 11:43:11 -0500
Subject: [PATCH] Fix issue 9898: false positive: knownConditionTrueFalse
 (#2806)

---
 lib/forwardanalyzer.cpp |  6 ++++--
 test/testvalueflow.cpp  | 13 +++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/lib/forwardanalyzer.cpp b/lib/forwardanalyzer.cpp
index 8b8b4c1c4..318c21b43 100644
--- a/lib/forwardanalyzer.cpp
+++ b/lib/forwardanalyzer.cpp
@@ -313,11 +313,13 @@ struct ForwardTraversal {
                 if (!scope)
                     return Progress::Break;
                 if (Token::Match(tok->link()->previous(), ")|else {")) {
-                    const bool inElse = Token::simpleMatch(tok->link()->previous(), "else {");
+                    const Token* tok2 = tok->link()->previous();
+                    const bool inElse = Token::simpleMatch(tok2, "else {");
+                    const bool inLoop = inElse ? false : Token::Match(tok2->link()->previous(), "while|for (");
                     Token* condTok = getCondTokFromEnd(tok);
                     if (!condTok)
                         return Progress::Break;
-                    if (!condTok->hasKnownIntValue()) {
+                    if (!condTok->hasKnownIntValue() || inLoop) {
                         if (!analyzer->lowerToPossible())
                             return Progress::Break;
                     } else if (condTok->values().front().intvalue == inElse) {
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 7cc852f39..7b5bdbe07 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -2479,6 +2479,19 @@ private:
                "}\n";
         ASSERT_EQUALS(false, testValueOfXImpossible(code, 8U, 0));
 
+        code = "int foo(int n) {\n"
+               "    if( n>= 8 ) {\n"
+               "        while(true) {\n"
+               "            n -= 8;\n"
+               "            if( n < 8 )\n"
+               "                break;\n"
+               "        }\n"
+               "        int x = n == 0;\n"
+               "        return x;\n"
+               "    }\n"
+               "}\n";
+        ASSERT_EQUALS(false, testValueOfXKnown(code, 9U, 0));
+
         code = "bool c();\n"
                "long f() {\n"
                "    bool stop = false;\n"