From d6a887e1f9549a26062c5ffe99f650f5ff3ccc34 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <danielm77@spray.se>
Date: Mon, 6 Feb 2012 07:32:29 +0100
Subject: [PATCH] Uninitialized variables: Fixed false positives when goto is
 simplified and inner condition is known to be true/false

---
 lib/checkuninitvar.cpp | 11 +++++++++++
 test/testuninitvar.cpp | 11 +++++++++++
 2 files changed, 22 insertions(+)

diff --git a/lib/checkuninitvar.cpp b/lib/checkuninitvar.cpp
index b64ac975b..a1a1cadc1 100644
--- a/lib/checkuninitvar.cpp
+++ b/lib/checkuninitvar.cpp
@@ -1088,6 +1088,9 @@ bool CheckUninitVar::checkScopeForVariable(const Token *tok, const unsigned int
 
     unsigned int number_of_if = 0;
 
+    // variables that are known to be non-zero
+    std::set<unsigned int> notzero;
+
     for (; tok; tok = tok->next()) {
         // End of scope..
         if (tok->str() == "}") {
@@ -1109,12 +1112,20 @@ bool CheckUninitVar::checkScopeForVariable(const Token *tok, const unsigned int
             continue;
         }
 
+        // assignment with nonzero constant..
+        if (Token::Match(tok, "[;{}] %var% = - %var% ;") && tok->next()->varId() > 0)
+            notzero.insert(tok->next()->varId());
+
         // Inner scope..
         if (Token::simpleMatch(tok, "if (")) {
             // initialization / usage in condition..
             if (checkIfForWhileHead(tok->next(), varid, ispointer, suppressErrors, bool(number_of_if == 0)))
                 return true;
 
+            // checking if a not-zero variable is zero => bail out
+            if (Token::Match(tok, "if ( %var% )") && notzero.find(tok->tokAt(2)->varId()) != notzero.end())
+                return true;   // this scope is not fully analysed => return true
+
             // goto the {
             tok = tok->next()->link()->next();
 
diff --git a/test/testuninitvar.cpp b/test/testuninitvar.cpp
index 5549a1846..671d612fa 100644
--- a/test/testuninitvar.cpp
+++ b/test/testuninitvar.cpp
@@ -1889,6 +1889,17 @@ private:
                         "}\n");
         TODO_ASSERT_EQUALS("error", "", errout.str());
 
+        // if goto is simplified there might be conditions that are always true
+        checkUninitVar2("void f() {\n"
+                        "    int i;\n"
+                        "    if (x) {\n"
+                        "        int y = -ENOMEM;\n"
+                        "        if (y != 0) return;\n"
+                        "        i++;\n"
+                        "    }\n"
+                        "}\n");
+        ASSERT_EQUALS("", errout.str());
+
         // for, while
         checkUninitVar2("void f() {\n"
                         "    int x;\n"