Fixed #2900 (found memory leak in kernel p54usb and a false positive reported)

lib/checkmemoryleak.cpp

@@ -1915,8 +1915,9 @@ void CheckMemoryLeakInFunction::simplifycode(Token *tok)
                     done = false;
                 }
 
-                // Remove "if { dealloc ; callfunc ; } !!else"
-                else if (Token::Match(tok2->next(), "if { dealloc|assign ; callfunc ; } !!else"))
+                // Remove "if { dealloc ; callfunc ; } !!else|return"
+                else if (Token::Match(tok2->next(), "if { dealloc|assign ; callfunc ; }") &&
+                         !Token::Match(tok2->tokAt(8), "else|return"))
                 {
                     Token::eraseTokens(tok2, tok2->tokAt(8));
                     done = false;

test/testmemleak.cpp

@@ -738,6 +738,10 @@ private:
         ASSERT_EQUALS("dealloc ; alloc ; return ; }", simplifycode("while1 { dealloc ; alloc ; } callfunc ; return ; }"));
         ASSERT_EQUALS("; }", simplifycode("loop callfunc ; }"));
 
+        // #2900 - don't report false positive
+        ASSERT_EQUALS("; alloc ; if { if { dealloc ; callfunc ; } return ; } dealloc ; }",
+                      simplifycode("; alloc ; if { if { dealloc ; callfunc ; } return ; } dealloc ; }"));
+
         // exit..
         ASSERT_EQUALS("; exit ;", simplifycode("; alloc; exit;"));
         ASSERT_EQUALS("; exit ;", simplifycode("; alloc; if { loop ; } dealloc; exit;"));