From 14a0031e884c765e8ef5705e5330dfc26f985e11 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Thu, 28 Feb 2019 10:26:47 +0100
Subject: [PATCH] Improved isVariableChangedByFunctionCall, better logic when
 parameter might be passed by reference

---
 lib/astutils.cpp      | 10 ++++++++--
 test/testastutils.cpp |  2 +-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/lib/astutils.cpp b/lib/astutils.cpp
index 8c5c43823..d7f712156 100644
--- a/lib/astutils.cpp
+++ b/lib/astutils.cpp
@@ -811,6 +811,8 @@ bool isVariableChangedByFunctionCall(const Token *tok, const Settings *settings,
     if (!tok)
         return false;
 
+    const Token * const tok1 = tok;
+
     // address of variable
     const bool addressOf = tok->astParent() && tok->astParent()->isUnaryOp("&");
 
@@ -844,10 +846,13 @@ bool isVariableChangedByFunctionCall(const Token *tok, const Settings *settings,
             tok = tok->link();
         else if (Token::Match(tok->previous(), "%name% ("))
             break;
+        else if (Token::simpleMatch(tok->previous(), "> (") && tok->previous()->link())
+            break;
         tok = tok->previous();
     }
     if (!tok || tok->str() != "(")
         return false;
+    const bool possiblyPassedByReference = (tok->next() == tok1 || Token::simpleMatch(tok->previous(), ", %name% [,)]"));
     tok = tok->previous();
     if (tok && tok->link() && tok->str() == ">")
         tok = tok->link()->previous();
@@ -879,12 +884,13 @@ bool isVariableChangedByFunctionCall(const Token *tok, const Settings *settings,
         // => it is assumed that parameter is an in parameter (TODO: this is a bad heuristic)
         if (!addressOf && settings && settings->library.isnullargbad(tok, 1+argnr))
             return false;
-        // addressOf => inconclusive
-        if (!addressOf) {
+        // possible pass-by-reference => inconclusive
+        if (possiblyPassedByReference) {
             if (inconclusive != nullptr)
                 *inconclusive = true;
             return false;
         }
+        // Safe guess: Assume that parameter is changed by function call
         return true;
     }
 
diff --git a/test/testastutils.cpp b/test/testastutils.cpp
index c5cf38415..a66e43fe3 100644
--- a/test/testastutils.cpp
+++ b/test/testastutils.cpp
@@ -135,7 +135,7 @@ private:
                "}";
         inconclusive = false;
         ASSERT_EQUALS(false, isVariableChangedByFunctionCall(code, "x ) ;", &inconclusive));
-        // FIXME : ASSERT_EQUALS(true, inconclusive);
+        ASSERT_EQUALS(true, inconclusive);
     }
 
     bool nextAfterAstRightmostLeaf(const char code[], const char parentPattern[], const char rightPattern[]) {