220 40345 <5df28d28-a2f4-47cd-9da7-49c91ed6d6f4@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Johnny Shaw Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: =?UTF-8?Q?=5Bstd=2Dproposals=5D_Enforce_explicit_casting_on_assignme?= =?UTF-8?Q?nt_and_return_type_=E2=80=98bool=E2=80=99?= Date: Fri, 5 Oct 2018 18:48:32 -0700 (PDT) Lines: 455 Approved: news@gmane.org Message-ID: <5df28d28-a2f4-47cd-9da7-49c91ed6d6f4@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1003_1879950856.1538790512417" X-Trace: blaine.gmane.org 1538790388 15944 195.159.176.226 (6 Oct 2018 01:46:28 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 6 Oct 2018 01:46:28 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBC527NWS3ELBB4NI4DOQKGQEJAPJ3ZA@isocpp.org Sat Oct 06 03:46:24 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw1-f71.google.com ([209.85.161.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1g8bfk-000441-EI for gclcip-std-proposals@m.gmane.org; Sat, 06 Oct 2018 03:46:24 +0200 Original-Received: by mail-yw1-f71.google.com with SMTP id b70-v6sf8099436ywh.3 for ; Fri, 05 Oct 2018 18:48:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=/uNECuZstQe1UBUIaE28+KwPhaUsicdLUP+zHayRJbc=; b=eC+jPIq1lF4VJ0zW8vyk1nhmZArVuMnFUsBiIzhCJ7gJWV7ybLKqE740V6GvlA2BBN yCTk1jZ4NQKkz+r4vr2awkM9oec4gB6C5gdSWDE27Yy6e2oIe9ea6n1VHOjTaI4HC6uM GE8lcY44mPHgGwz9/Uws26/d6KwFJe14MGN3AGEPrfciIOcePL7v+L+oj+1WgkCwaBnW YcMmj+iJBTqK5tMvtUV53I5O8X0VkbMtIl92xJLrLSRDzM20iCoZwatm/3l57OOh5LgD iQ70NM0A1cihhqmb/x0394waUueG3jlrENQDm6wNtVXQQll1MHItRXQe3DRV0D5LsG2o KI5Q== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=/uNECuZstQe1UBUIaE28+KwPhaUsicdLUP+zHayRJbc=; b=XEZFAKbwv3zKsXTVD2TJWSSECBTr/IazkSNrmLWJb6CQIxsEGKO0A53HGUoiDVeJ9h Gub/xVyN988EW/Zq2fNRg8OO3odNkdrvNLZyDMKOJC16/fndmSw9ch0Y0N2B47ZQcy1b uvZydQdJwO3q0Olo9Xso0eoA7kVhKXVLybOG48/SACE8wtxlAZZkb3UiADBPInbA0Vwc 6KCoim1R+gT7Qk8gSMNZtVyfMffqTfg7qyU5xYOLWhYIp9S+W0d9QBekYuEr1VnhZcl3 bWAbXMkxNbhGghbj7OnWPX7LKUobgO/zVK68xkeOFM0fy3FtaLVF0GZk/CiJPQAEnMzV Si8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=/uNECuZstQe1UBUIaE28+KwPhaUsicdLUP+zHayRJbc=; b=fkw8Xrtx+RRxvEs7EVCyYCiYPQoaoZw4CRNAUSIMubOn1kOvaGy7/3Cv4VUEJgPTkx MaOCnfXQ5B+xdiTYiGxBPVbI656389QaIyBOSF7JCwyONSqJDuAr/jZ/Mc2vqg6h5FxB VDaswTTfBWFkPtdni7jrWMJoeyNbylCOPIIuz/aio4SaY0Z6GFtEoO6fP+gu3sGKX0Q1 owGQDDZmsX87VbXG+WWv3hI/HcpZxgF7zvCiCexuf84SB8qiTn86EQLo8B3sEPdw1Z5c KLQiX5S0hKosq3lvCf9LYmPli7Yp9/wHlvsDfHLEsRbgqMM5q2Ed0Fejp5j1vU597rzl c2Mg== X-Gm-Message-State: ABuFfoiFroLTduyLfdO8n8JtQCtswxsNLCjWxEyBiJMQCLum/lFf9mo7 cBv+v+c2aE82v9flLttiAcoRCw== X-Google-Smtp-Source: ACcGV61nKoHLAX9qYVkDM7zV/vEoe1GG0Wb04Z8SjT/tcIyJYcXuTWyaZ4nlbtnFJqtcL4EgpQiAJw== X-Received: by 2002:a25:390a:: with SMTP id g10-v6mr8005205yba.40.1538790514604; Fri, 05 Oct 2018 18:48:34 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a25:8081:: with SMTP id n1-v6ls2676984ybk.21.gmail; Fri, 05 Oct 2018 18:48:33 -0700 (PDT) X-Received: by 2002:a25:1c83:: with SMTP id c125-v6mr144142ybc.6.1538790512902; Fri, 05 Oct 2018 18:48:32 -0700 (PDT) X-Original-Sender: JohnnyShaw02@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:40345 Archived-At: ------=_Part_1003_1879950856.1538790512417 Content-Type: multipart/alternative; boundary="----=_Part_1004_845694214.1538790512418" ------=_Part_1004_845694214.1538790512418 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Recently I=E2=80=99ve noticed some interpretations of the following standar= ds=20 resulting in removing of compiler warnings around implicit conversions to a= =20 =E2=80=98bool=E2=80=99 type: =20 1) C++14 =C2=A74.12/1 =E2=80=9CA zero value, null pointer value, or null me= mber pointer=20 value is converted to false; any other value is converted to true. For=20 direct-initialization (8.5), a prvalue of type std::nullptr_t can be=20 converted to a prvalue of type bool; the resulting value is false.=E2=80=9D 2) C99 and C11 =C2=A76.3.1.2/1 =E2=80=9CWhen any scalar value is converted = to _Bool, the=20 result is 0 if the value compares equal to 0; otherwise, the result is 1.= =E2=80=9D =20 Specifically, the VS1017 compiler has removed the following warning=20 completely: https://msdn.microsoft.com/en-us/library/b6801kcy.aspx =20 Over correspondence with Microsoft I=E2=80=99ve noticed it my be due to dir= ect=20 interpretation of standards. See: https://developercommunity.visualstudio.com/content/problem/346302/vs2017-1= 58-c-fails-to-warn-when-forcing-int-to-boo.html https://developercommunity.visualstudio.com/content/problem/349342/visual-s= tudio-2017-158-allows-implicit-conversion.html =20 This is moving the bar backward a bit, resulting in unintended bugs being= =20 overlooked that would have previously been caught by the compiler. =20 While there is value in implicit conversion under some circumstances.=20 Explicit conversion clearly identifies the intent and eliminates mistakes.= =20 Enforcing a standard that requires explicit conversion to bool, at very=20 least for a return value, will eliminate possible coding errors. The=20 following are some mundane examples and could be overlooked with given more= =20 complex code: =20 bool TestFunc(int a) { return a;=20 }=20 bool TestFuncNotOver100(int a)=20 {=20 if (a > 100)=20 {=20 return a; }=20 return true;=20 }=20 bool TestPointerForNull(void* pvX)=20 { if (nullptr !=3D pvX)=20 { return false;=20 }=20 return pvX;=20 } =20 At very least requiring a check against a matching type by boolean=20 operation, for example: bool TestFunc(int a) { return (0 =3D=3D a);=20 } =20 Or for assignment: =20 int a =3D 1; bool bValue =3D (0 =3D=3D a); =20 Moreover, requiring an explicit cast: =20 bool TestFunc(int a) { return static_cast(a);=20 } --=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/5df28d28-a2f4-47cd-9da7-49c91ed6d6f4%40isocpp.or= g. ------=_Part_1004_845694214.1538790512418 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

Recently I=E2=80=99ve noticed some interpretations of the following standards resulting in removing of compile= r warnings around implicit conversions to a =E2=80=98bool=E2=80=99 type:=

=C2=A0

1)=C2=A0C++14 =C2=A74.12/1 =E2=80=9CA zero value, null pointer value, or null member poin= ter value is converted to=C2=A0false<= /code>; any oth= er value is converted to=C2=A0true. For direct-initialization (8.5), a prvalue of type=C2=A0<= code>std::nullptr_t<= span style=3D"font-size: 9pt; font-family: Arial, sans-serif; color: rgb(36= , 39, 41); background-image: initial; background-position: initial; backgro= und-size: initial; background-repeat: initial; background-attachment: initi= al; background-origin: initial; background-clip: initial;">=C2=A0can be con= verted to a prvalue of type=C2=A0bool; the resulting value is=C2=A0false.=E2=80=9D
2)=C2=A0C99 and C11 =C2=A76.3.1.2/1 =E2=80=9CWhen any scalar value is converted to=C2=A0_Bool, the result is 0 if= the value compares equal to 0; otherwise, the result is 1.=E2=80=9D

=C2=A0

Specifically, the VS1017 compiler has removed the following warning completely:

https://msdn.microsoft.com/en-us/library/b6801kcy.aspx

=C2=A0

Over correspondence with Microsoft I=E2=80=99ve noticed it my be due to direct interpretation of standards. See:

https://developercommunity.visualstudio.com/content/problem/346302/= vs2017-158-c-fails-to-warn-when-forcing-int-to-boo.html

https://developercommunity.visualstudio.com/content/problem/349342/v= isual-studio-2017-158-allows-implicit-conversion.html

=C2=A0

This is moving the bar backward a bit, resulting in unintended bugs being overlooked that would have previously be= en caught by the compiler.

=C2=A0

While there is value in implicit conversion under some circumstances. Explicit conversion clearly identifies= the intent and eliminates mistakes. Enforcing a standard that requires explicit conversion to bool, at very least for a return value, will eliminate possib= le coding errors. The following are some mundane examples and could be overloo= ked with given more complex code:

=C2=A0

bool TestFunc(int a)
{
=C2=A0 =C2=A0 return a;
}
bool<= /span> TestFuncNotOver100(int a)
{
=C2=A0 =C2=A0 if (a= > 100)
=C2=A0 =C2=A0 {
=C2=A0 =C2=A0 =C2=A0 = =C2=A0 return= a;=
=C2=A0 =C2=A0= }<= span style=3D"color: #000;" class=3D"styled-by-prettify">
=C2=A0 =C2=A0= return true;
}

bool TestPointerForNull(void* pvX)
{
=C2=A0 =C2=A0 if (nullptr !=3D pvX)
=C2=A0 = =C2=A0 {
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 return fa= lse;
=C2=A0 =C2= =A0 }
=C2=A0 =C2= =A0 return= pvX;
}
<= p class=3D"MsoNormal">

=C2=A0

At very least requiring a check against a matching type by boolean operation, for example:


bool TestFunc(int a)
{
=C2=A0 =C2=A0 return (0 =3D=3D a);
}

<= br>

=C2=A0

Or for assignment:

=C2=A0

int a =3D 1;
bool bValue =3D = (0 =3D=3D a);


=C2=A0

Moreover, requiring an explicit cast:

=C2=A0

bool TestFunc(int a)
{
=C2=A0 =C2=A0 return sta= tic_cast&l= t;bool>= (a<= span style=3D"color: #660;" class=3D"styled-by-prettify">);
}


--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/5df28d28-a2f4-47cd-9da7-49c91ed6d6f4= %40isocpp.org.
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