From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-help-return-64572-listarch-gcc-help=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 129415 invoked by alias); 29 Dec 2019 05:12:04 -0000
Mailing-List: contact gcc-help-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-help.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-help/>
List-Post: <mailto:gcc-help@gcc.gnu.org>
List-Help: <mailto:gcc-help-help@gcc.gnu.org>
Sender: gcc-help-owner@gcc.gnu.org
Received: (qmail 129308 invoked by uid 89); 29 Dec 2019 05:12:03 -0000
Authentication-Results: sourceware.org; auth=none
X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.1 spammy=HX-Received:620a
X-HELO: mail-qk1-f173.google.com
Received: from mail-qk1-f173.google.com (HELO mail-qk1-f173.google.com) (209.85.222.173) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Sun, 29 Dec 2019 05:12:02 +0000
Received: by mail-qk1-f173.google.com with SMTP id x1so24243931qkl.12        for <gcc-help@gcc.gnu.org>; Sat, 28 Dec 2019 21:12:02 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;        d=gmail.com; s=20161025;        h=mime-version:from:date:message-id:subject:to;        bh=Pvn7FoAPvOlc2gipUiL/JSAwc/4OrCeDxHaTbSOiMtU=;        b=DfYgcpSyJGomqXnNl9m2/+I8dnkjy0hNEandkIZJfQdFl5+dJKktDCDtKs5FAc9HFQ         5GEcbp/8292tavieAphJfS5n5SvDrbULQgesfwX6fl80aGGPzxTWqFpVh7iz1G/OTTTe         bG+4tTcn9/3suq8ED0sMzKuNk6plx9bQSLSF3dLEj/lphpkw1QQN+RGLAcp88fdbpQ2p         Qp4MmyNY0P7RTMN4K1GgL1Al6wvtrXKRLMEydCWjGPRrZ9NUMWLskP5lthhqYmwm3Zce         kgVzkmRCuameTfEtC8NgovQs78BUxmL7bTiWRtMdqtfgLpWHmy2k9VOz+jER91sbTAXm         Z43Q==
MIME-Version: 1.0
From: Yubin Ruan <ablacktshirt@gmail.com>
Date: Sun, 29 Dec 2019 05:12:00 -0000
Message-ID: <CAJYFCiO_ZGzifxLffJeAKcF1ywMmf03zDJTC569TRU8c=HKKrQ@mail.gmail.com>
Subject: gcc warning about return value truncation
To: gcc-help@gcc.gnu.org
Content-Type: text/plain; charset="UTF-8"
X-IsSubscribed: yes
X-SW-Source: 2019-12/txt/msg00121.txt.bz2

Is there any gcc flag to warn about this?

#include <iostream>
#include <cstdint>

int16_t func() {
    int32_t num = INT32_MAX;
    std::cout << "func() called " << num << std::endl;
    return num;
}

int main()
{
    int32_t val = func();
    std::cout << "return value is " << val << std::endl;
}

The return value of func() was truncated because the return type is
accidentally written as int16_t

Thanks,
Yubin