From c6f7a78ebb1a0b4094af2773cdd9fe2fde4a5979 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Sat, 10 Jul 2021 08:36:54 +0200
Subject: [PATCH] missingReturn; Fixed false positives

---
 lib/checkfunctions.cpp | 20 ++++++++++++--------
 lib/token.h            |  6 ------
 test/testfunctions.cpp | 15 +++++++++++++++
 3 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/lib/checkfunctions.cpp b/lib/checkfunctions.cpp
index 160652e19..25fbce3f3 100644
--- a/lib/checkfunctions.cpp
+++ b/lib/checkfunctions.cpp
@@ -271,21 +271,26 @@ void CheckFunctions::checkMissingReturn()
 
 static const Token *checkMissingReturnScope(const Token *tok)
 {
-    tok = tok->previous();
-    while (tok) {
+    const Token *lastStatement = nullptr;
+    while ((tok = tok->previous()) != nullptr) {
         if (tok->str() == "{")
-            return tok->next();
+            return lastStatement ? lastStatement : tok->next();
         if (tok->str() == "}") {
             for (const Token *prev = tok->link()->previous(); prev && prev->scope() == tok->scope() && !Token::Match(prev, "[;{}]"); prev = prev->previous()) {
                 if (prev->isKeyword() && Token::Match(prev, "return|throw"))
                     return nullptr;
             }
             if (tok->scope()->type == Scope::ScopeType::eSwitch) {
-                // find break/default
+                // find reachable break / !default
                 bool hasDefault = false;
+                bool reachable = false;
                 for (const Token *switchToken = tok->link(); switchToken != tok; switchToken = switchToken->next()) {
-                    if (Token::simpleMatch(switchToken, "break ;"))
+                    if (reachable && Token::simpleMatch(switchToken, "break ;"))
                         return switchToken;
+                    if (switchToken->isKeyword() && Token::Match(switchToken, "return|throw"))
+                        reachable = false;
+                    if (Token::Match(switchToken, "case|default"))
+                        reachable = true;
                     if (Token::simpleMatch(switchToken, "default :"))
                         hasDefault = true;
                     else if (switchToken->str() == "{" && switchToken->scope()->isLoopScope())
@@ -309,9 +314,8 @@ static const Token *checkMissingReturnScope(const Token *tok)
         }
         if (tok->isKeyword() && Token::Match(tok, "return|throw"))
             return nullptr;
-        if (Token::Match(tok, "; !!}"))
-            return tok->next();
-        tok = tok->previous();
+        if (Token::Match(tok, "; !!}") && !lastStatement)
+            lastStatement = tok->next();
     }
     return nullptr;
 }
diff --git a/lib/token.h b/lib/token.h
index 77ca6e107..751e1ae64 100644
--- a/lib/token.h
+++ b/lib/token.h
@@ -385,12 +385,6 @@ public:
                                         mTokType == eBoolean || mTokType == eLiteral || mTokType == eEnumerator);
         setFlag(fIsLiteral, memoizedIsLiteral);
     }
-    void isKeyword(const bool kwd) {
-        if (kwd)
-            tokType(eKeyword);
-        else if (mTokType == eKeyword)
-            tokType(eName);
-    }
     bool isKeyword() const {
         return mTokType == eKeyword;
     }
diff --git a/test/testfunctions.cpp b/test/testfunctions.cpp
index b82aba677..5422fd15b 100644
--- a/test/testfunctions.cpp
+++ b/test/testfunctions.cpp
@@ -1379,6 +1379,13 @@ private:
         check("auto foo4() -> void {}");
         ASSERT_EQUALS("", errout.str());
 
+        // unreachable code..
+        check("int foo(int x) {\n"
+              "  return 1;\n"
+              "  (void)x;\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
+
         // switch
         check("int f() {\n"
               "    switch (x) {\n"
@@ -1388,6 +1395,14 @@ private:
               "}");
         ASSERT_EQUALS("[test.cpp:3]: (error) Found a exit path from function with non-void return type that has missing return statement\n", errout.str());
 
+        check("int f() {\n"
+              "    switch (x) {\n"
+              "        case 1: return 2; break;\n"
+              "        default: return 1;\n"
+              "    }\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
+
         // if/else
         check("int f(int x) {\n"
               "    if (x) {\n"