Fixed #1023 (improve check: Unintialized variable not detected when using +=)

lib/checkother.cpp

@@ -1625,6 +1625,26 @@ private:
                 return &tok;
             }
 
+            // += etc
+            if (Token::Match(tok.previous(), "[;{}]") || Token::Match(tok.tokAt(-2), "[;{}] *"))
+            {
+                // goto the equal..
+                const Token *eq = tok.next();
+                if (eq && eq->str() == "[" && eq->link() && eq->link()->next())
+                    eq = eq->link()->next();
+
+                // is it X=
+                if (Token::Match(eq, "+=|-=|*=|/=|&=|^=") || eq->str() == "|=")
+                {
+                    if (tok.previous()->str() == "*")
+                        use_pointer(foundError, checks, &tok);
+                    else if (tok.next()->str() == "[")
+                        use_array(foundError, checks, &tok);
+                    else
+                        use(foundError, checks, &tok);
+                }
+            }
+
             if (Token::Match(tok.next(), "= malloc|kmalloc") || Token::simpleMatch(tok.next(), "= new char ["))
             {
                 alloc_pointer(checks, tok.varId());

test/testother.cpp

@@ -1184,6 +1184,28 @@ private:
                        "}\n");
         ASSERT_EQUALS("", errout.str());
 
+        // +=
+        checkUninitVar("void f()\n"
+                       "{\n"
+                       "    int c;\n"
+                       "    c += 2;\n"
+                       "}\n");
+        ASSERT_EQUALS("[test.cpp:4]: (error) Uninitialized variable: c\n", errout.str());
+
+        checkUninitVar("void f()\n"
+                       "{\n"
+                       "    char *s = malloc(100);\n"
+                       "    *s += 10;\n"
+                       "}\n");
+        ASSERT_EQUALS("[test.cpp:4]: (error) Data is allocated but not initialized: s\n", errout.str());
+
+        checkUninitVar("void f()\n"
+                       "{\n"
+                       "    int a[10];\n"
+                       "    a[0] += 10;\n"
+                       "}\n");
+        ASSERT_EQUALS("[test.cpp:4]: (error) Uninitialized variable: a\n", errout.str());
+
         // goto..
         checkUninitVar("void foo(int x)\n"
                        "{\n"