From 078a6d780441794cd484d5c561edba66ccbdf87c Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Sun, 7 Aug 2022 19:06:19 +0200
Subject: [PATCH] Fix #11238 FP knownConditionTrueFalse with constexpr? (#4341)

---
 lib/astutils.cpp       | 20 +++++++++++---------
 lib/astutils.h         |  2 +-
 lib/checkcondition.cpp |  4 +++-
 test/testcondition.cpp |  8 ++++++++
 4 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/lib/astutils.cpp b/lib/astutils.cpp
index 00658a6d8..e947dc4bc 100644
--- a/lib/astutils.cpp
+++ b/lib/astutils.cpp
@@ -2768,35 +2768,37 @@ bool isCPPCast(const Token* tok)
     return tok && Token::simpleMatch(tok->previous(), "> (") && tok->astOperand2() && tok->astOperand1() && isCPPCastKeyword(tok->astOperand1());
 }
 
-bool isConstVarExpression(const Token *tok, const char* skipMatch)
+bool isConstVarExpression(const Token *tok, std::function<bool(const Token*)> skipPredicate)
 {
     if (!tok)
         return false;
     if (tok->str() == "?" && tok->astOperand2() && tok->astOperand2()->str() == ":") // ternary operator
         return isConstVarExpression(tok->astOperand2()->astOperand1()) && isConstVarExpression(tok->astOperand2()->astOperand2()); // left and right of ":"
-    if (skipMatch && Token::Match(tok, skipMatch))
+    if (skipPredicate && skipPredicate(tok))
         return false;
     if (Token::simpleMatch(tok->previous(), "sizeof ("))
         return true;
     if (Token::Match(tok->previous(), "%name% (")) {
-        if (Token::simpleMatch(tok->astOperand1(), ".") && !isConstVarExpression(tok->astOperand1(), skipMatch))
+        if (Token::simpleMatch(tok->astOperand1(), ".") && !isConstVarExpression(tok->astOperand1(), skipPredicate))
             return false;
         std::vector<const Token *> args = getArguments(tok);
+        if (args.empty() && tok->previous()->function() && tok->previous()->function()->isConstexpr())
+            return true;
         return std::all_of(args.begin(), args.end(), [&](const Token* t) {
-            return isConstVarExpression(t, skipMatch);
+            return isConstVarExpression(t, skipPredicate);
         });
     }
     if (isCPPCast(tok)) {
-        return isConstVarExpression(tok->astOperand2(), skipMatch);
+        return isConstVarExpression(tok->astOperand2(), skipPredicate);
     }
     if (Token::Match(tok, "( %type%"))
-        return isConstVarExpression(tok->astOperand1(), skipMatch);
+        return isConstVarExpression(tok->astOperand1(), skipPredicate);
     if (tok->str() == "::" && tok->hasKnownValue())
-        return isConstVarExpression(tok->astOperand2(), skipMatch);
+        return isConstVarExpression(tok->astOperand2(), skipPredicate);
     if (Token::Match(tok, "%cop%|[|.")) {
-        if (tok->astOperand1() && !isConstVarExpression(tok->astOperand1(), skipMatch))
+        if (tok->astOperand1() && !isConstVarExpression(tok->astOperand1(), skipPredicate))
             return false;
-        if (tok->astOperand2() && !isConstVarExpression(tok->astOperand2(), skipMatch))
+        if (tok->astOperand2() && !isConstVarExpression(tok->astOperand2(), skipPredicate))
             return false;
         return true;
     }
diff --git a/lib/astutils.h b/lib/astutils.h
index c30242f3b..9fbf706a8 100644
--- a/lib/astutils.h
+++ b/lib/astutils.h
@@ -383,7 +383,7 @@ bool isLikelyStreamRead(bool cpp, const Token *op);
 
 bool isCPPCast(const Token* tok);
 
-bool isConstVarExpression(const Token *tok, const char * skipMatch = nullptr);
+bool isConstVarExpression(const Token* tok, std::function<bool(const Token*)> skipPredicate = nullptr);
 
 const Variable *getLHSVariable(const Token *tok);
 
diff --git a/lib/checkcondition.cpp b/lib/checkcondition.cpp
index 44d8b2cbd..1c88ba038 100644
--- a/lib/checkcondition.cpp
+++ b/lib/checkcondition.cpp
@@ -1497,7 +1497,9 @@ void CheckCondition::alwaysTrueFalse()
                 continue;
             if (tok->isComparisonOp() && isSameExpression(mTokenizer->isCPP(), true, tok->astOperand1(), tok->astOperand2(), mSettings->library, true, true))
                 continue;
-            if (isConstVarExpression(tok, "[|(|&|+|-|*|/|%|^|>>|<<"))
+            if (isConstVarExpression(tok, [](const Token* tok) {
+                return Token::Match(tok, "[|(|&|+|-|*|/|%|^|>>|<<") && !Token::simpleMatch(tok, "( )");
+            }))
                 continue;
 
             // there are specific warnings about nonzero expressions (pointer/unsigned)
diff --git a/test/testcondition.cpp b/test/testcondition.cpp
index cb508786d..42a57e186 100644
--- a/test/testcondition.cpp
+++ b/test/testcondition.cpp
@@ -4281,6 +4281,14 @@ private:
               "    }\n"
               "};\n");
         ASSERT_EQUALS("", errout.str());
+
+        check("constexpr int f() {\n" // #11238
+              "    return 1;\n"
+              "}\n"
+              "constexpr bool g() {\n"
+              "    return f() == 1;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void alwaysTrueSymbolic()