From ff0eee4d7720716cb04a9cd2240cb6a1b2103767 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Sat, 18 Feb 2023 17:35:12 +0100
Subject: [PATCH] Fix #11558 FP knownConditionTrueFalse when checking for zero
 character (#4794)

* Fix #11558 FP knownConditionTrueFalse when checking for zero characte

* Fix test

* Set impossible value only for non-Boolean conditions, rename

* Fix condition
---
 lib/valueflow.cpp      |  8 +++++++-
 test/testcondition.cpp | 10 ++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index f295278be..74e923f3d 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -5033,11 +5033,16 @@ static const Token* findIncompleteVar(const Token* start, const Token* end)
 static ValueFlow::Value makeConditionValue(long long val,
                                            const Token* condTok,
                                            bool assume,
+                                           bool impossible = false,
                                            const Settings* settings = nullptr,
                                            SourceLocation loc = SourceLocation::current())
 {
     ValueFlow::Value v(val);
     v.setKnown();
+    if (impossible) {
+        v.intvalue = !v.intvalue;
+        v.setImpossible();
+    }
     v.condition = condTok;
     if (assume)
         v.errorPath.emplace_back(condTok, "Assuming condition '" + condTok->expressionString() + "' is true");
@@ -5116,7 +5121,8 @@ static void valueFlowConditionExpressions(TokenList *tokenlist, SymbolDatabase*
             {
                 for (const Token* condTok2 : getConditions(condTok, "&&")) {
                     if (is1) {
-                        SameExpressionAnalyzer a1(condTok2, makeConditionValue(1, condTok2, true), tokenlist);
+                        const bool isBool = astIsBool(condTok2) || Token::Match(condTok2, "%comp%|%oror%|&&");
+                        SameExpressionAnalyzer a1(condTok2, makeConditionValue(1, condTok2, /*assume*/ true, !isBool), tokenlist); // don't set '1' for non-boolean expressions
                         valueFlowGenericForward(startTok, startTok->link(), a1, settings);
                     }
 
diff --git a/test/testcondition.cpp b/test/testcondition.cpp
index f5da61c95..34a114c0c 100644
--- a/test/testcondition.cpp
+++ b/test/testcondition.cpp
@@ -4483,6 +4483,16 @@ private:
               "    g(s ? s->get() : 0);\n"
               "}\n");
         ASSERT_EQUALS("[test.cpp:5] -> [test.cpp:7]: (style) Condition 's' is always true\n", errout.str());
+
+        check("void f(const char* o) {\n" // #11558
+              "    if (!o || !o[0])\n"
+              "        return;\n"
+              "    if (o[0] == '-' && o[1]) {\n"
+              "        if (o[1] == '-') {}\n"
+              "        if (o[1] == '\\0') {}\n"
+              "    }\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:6]: (style) Condition 'o[1]=='\\0'' is always false\n", errout.str());
     }
 
     void alwaysTrueSymbolic()