From 529b255e9901c9eaba7febfb7ef54a9eb79c0b98 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Fri, 25 Aug 2017 23:07:26 +0200
Subject: [PATCH] ValueFlow: Better errorpath for increment/decrement

---
 lib/valueflow.cpp      | 10 ++++++++--
 test/testvalueflow.cpp |  3 +++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 8433b993c..753a2f6b9 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -959,15 +959,21 @@ static void valueFlowReverse(TokenList *tokenlist,
             }
 
             // increment/decrement
+            int inc = 0;
             if (Token::Match(tok2->previous(), "[;{}] %name% ++|-- ;"))
-                val.intvalue += (tok2->strAt(1)=="++") ? -1 : 1;
+                inc = (tok2->strAt(1)=="++") ? -1 : 1;
             else if (Token::Match(tok2->tokAt(-2), "[;{}] ++|-- %name% ;"))
-                val.intvalue += (tok2->strAt(-1)=="++") ? -1 : 1;
+                inc = (tok2->strAt(-1)=="++") ? -1 : 1;
             else if (Token::Match(tok2->previous(), "++|-- %name%") || Token::Match(tok2, "%name% ++|--")) {
                 if (settings->debugwarnings)
                     bailout(tokenlist, errorLogger, tok2, "increment/decrement of " + tok2->str());
                 break;
             }
+            if (inc != 0) {
+                val.intvalue += inc;
+                const std::string info(tok2->str() + " is " + std::string(inc==1 ? "decremented" : "incremented") + ", before this " + (inc==1?"decrement":"increment") + " the value is " + val.infoString());
+                val.errorPath.push_back(ErrorPathItem(tok2, info));
+            }
 
             // compound assignment
             if (Token::Match(tok2->previous(), "[;{}] %var% %assign%") && tok2->next()->str() != "=") {
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index beb96ea80..d190aa083 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -730,6 +730,9 @@ private:
                "   if (x == 4);\n"
                "}";
         ASSERT_EQUALS(true, testValueOfX(code, 2U, 3));
+        ASSERT_EQUALS("4,Assuming that condition 'x==4' is not redundant\n"
+                      "3,x is incremented, before this increment the value is 3\n",
+                      getErrorPathForX(code, 2U));
 
         // compound assignment += , -= , ...
         code = "void f(int x) {\n"