From 3d0c1a33017780f77f01618e66db1e4bd5e201fa Mon Sep 17 00:00:00 2001
From: Erik Lax <erik@datahack.se>
Date: Sun, 1 Jan 2012 00:11:03 +0200
Subject: [PATCH] Fix #3457 (Statement following goto can be executed)
 http://sourceforge.net/apps/trac/cppcheck/ticket/3457

---
 lib/checkother.cpp | 22 ++++++++++++++++++++--
 test/testother.cpp | 27 +++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/lib/checkother.cpp b/lib/checkother.cpp
index 13586e8dc..f5b89223d 100644
--- a/lib/checkother.cpp
+++ b/lib/checkother.cpp
@@ -1591,6 +1591,7 @@ void CheckOther::checkUnreachableCode()
 
     for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
         const Token* secondBreak = 0;
+        const Token* labelName = 0;
         if (tok->str() == "(")
             tok = tok->link();
         else if (Token::Match(tok, "break|continue ;"))
@@ -1602,8 +1603,10 @@ void CheckOther::checkUnreachableCode()
                     secondBreak = tok2->next();
                     break;
                 }
-        } else if (Token::Match(tok, "goto %any% ;"))
+        } else if (Token::Match(tok, "goto %any% ;")) {
             secondBreak = tok->tokAt(3);
+            labelName = tok->tokAt(1);
+        }
 
         if (secondBreak) {
             if (Token::Match(secondBreak, "continue|goto|throw") ||
@@ -1630,7 +1633,22 @@ void CheckOther::checkUnreachableCode()
                 }
                 tok = Token::findmatch(secondBreak, "[}:]");
             } else if (!Token::Match(secondBreak, "return|}|case|default") && secondBreak->strAt(1) != ":") { // TODO: No bailout for unconditional scopes
-                unreachableCodeError(secondBreak);
+                // If the goto label is followed by a loop construct in which the label is defined it's quite likely
+                // that the goto jump was intended to skip some code on the first loop iteration.
+                bool labelInFollowingLoop = false;
+                if (labelName && Token::Match(secondBreak, "while|do|for")) {
+                    const Token *scope = Token::findmatch(secondBreak, "{");
+                    if (scope) {
+                        for (const Token *tokIter = scope; tokIter != scope->link() && tokIter; tokIter = tokIter->next()) {
+                            if (Token::Match(tokIter, "[;{}] %any% :") && labelName->str() == tokIter->strAt(1)) {
+                                labelInFollowingLoop = true;
+                                break;
+                            }
+                        }
+                    }
+                }
+                if (!labelInFollowingLoop)
+                    unreachableCodeError(secondBreak);
                 tok = Token::findmatch(secondBreak, "[}:]");
             } else
                 tok = secondBreak;
diff --git a/test/testother.cpp b/test/testother.cpp
index a47d3f6c0..871da44e1 100644
--- a/test/testother.cpp
+++ b/test/testother.cpp
@@ -1919,6 +1919,33 @@ private:
               "}");
         ASSERT_EQUALS("", errout.str());
 
+        check("int foo() {\n"
+              "    goto label;\n"
+              "    while (true) {\n"
+              "     bar();\n"
+              "     label:\n"
+              "    }\n"
+              "}");
+        ASSERT_EQUALS("", errout.str()); // #3457
+
+        check("int foo() {\n"
+              "    goto label;\n"
+              "    do {\n"
+              "     bar();\n"
+              "     label:\n"
+              "    } while (true);\n"
+              "}");
+        ASSERT_EQUALS("", errout.str()); // #3457
+
+        check("int foo() {\n"
+              "    goto label;\n"
+              "    for (;;) {\n"
+              "     bar();\n"
+              "     label:\n"
+              "    }\n"
+              "}");
+        ASSERT_EQUALS("", errout.str()); // #3457
+
         check("%: return ; ()"); // Don't crash. #3441.
     }