From 89532cf8b922da365abe1b16b118125a88c1ffc6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Tue, 25 Apr 2017 20:45:02 +0200
Subject: [PATCH] Fixed #7968 (valueFlowBeforeCondition: better handling of
 compound assignments)

---
 lib/valueflow.cpp      | 23 +++++++++++++++++++++++
 test/testvalueflow.cpp | 29 +++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 0b32323b3..bcfc161b8 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -940,6 +940,29 @@ static void valueFlowReverse(TokenList *tokenlist,
                 break;
             }
 
+            // compound assignment
+            if (Token::Match(tok2->previous(), "[;{}] %var% %assign%") && tok2->next()->str() != "=") {
+                const Token * const assignToken = tok2->next();
+                const Token * const rhsToken = assignToken->astOperand2();
+                if (!rhsToken || !rhsToken->hasKnownIntValue()) {
+                    if (settings->debugwarnings)
+                        bailout(tokenlist, errorLogger, tok2, "compound assignment, rhs value is not known");
+                    break;
+                }
+                const MathLib::bigint rhsValue =  rhsToken->values().front().intvalue;
+                if (assignToken->str() == "+=")
+                    val.intvalue -= rhsValue;
+                else if (assignToken->str() == "-=")
+                    val.intvalue += rhsValue;
+                else if (assignToken->str() == "*=")
+                    val.intvalue /= rhsValue;
+                else {
+                    if (settings->debugwarnings)
+                        bailout(tokenlist, errorLogger, tok2, "compound assignment " + tok2->str());
+                    break;
+                }
+            }
+
             // bailout: variable is used in rhs in assignment to itself
             if (bailoutSelfAssignment(tok2)) {
                 if (settings->debugwarnings)
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 3bf51af4a..00d111f94 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -628,6 +628,35 @@ private:
                "}";
         ASSERT_EQUALS(true, testValueOfX(code, 2U, 3));
 
+        // compound assignment += , -= , ...
+        code = "void f(int x) {\n"
+               "   a = x;\n"
+               "   x += 2;\n"
+               "   if (x == 4);\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 2U, 2));
+
+        code = "void f(int x) {\n"
+               "   a = x;\n"
+               "   x -= 2;\n"
+               "   if (x == 4);\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 2U, 6));
+
+        code = "void f(int x) {\n"
+               "   a = x;\n"
+               "   x *= 2;\n"
+               "   if (x == 42);\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 2U, 21));
+
+        code = "void f(int x) {\n"
+               "   a = x;\n"
+               "   x /= 5;\n"
+               "   if (x == 42);\n"
+               "}";
+        ASSERT(tokenValues(code, "x ;").empty());
+
         // bailout: assignment
         bailout("void f(int x) {\n"
                 "    x = y;\n"