220 41478 <518a0db5-b7f2-470f-b0be-606f66f1c786@isocpp.org> article Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Kristen Wegner Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: exception classes Date: Wed, 20 Feb 2019 10:28:38 -0800 (PST) Approved: news@gmane.org Message-ID: <518a0db5-b7f2-470f-b0be-606f66f1c786@isocpp.org> Reply-To: std-proposals@isocpp.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_63_2021104249.1550687318711" Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="2593"; mail-complaints-to="usenet@blaine.gmane.org" To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCGYZOM5TUARBV5YW3RQKGQE2IOROPA@isocpp.org Wed Feb 20 19:28:43 2019 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb1-f197.google.com ([209.85.219.197]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.89) (envelope-from ) id 1gwWbq-0000VI-NN for gclcip-std-proposals@m.gmane.org; Wed, 20 Feb 2019 19:28:43 +0100 Original-Received: by mail-yb1-f197.google.com with SMTP id z16sf5850556ybp.12 for ; Wed, 20 Feb 2019 10:28:42 -0800 (PST) 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=bOtt/hBntAv92axjJjSWGG95dNOUsappt5O5csvAlfM=; b=E5ZbJckbmN53uN3LVVV43KxiYfOgxnxOWOznBhXyjDfoFuVum47u032R8Eriybpf++ 8uZoKuTCTmZaUU26x+zoDDe5hZSXEfUrq0gK6qnlbPJ2i8ItT9KsxIHJSAXJE/FoNmI6 T6UP7vC5Tkos8+54W52LvWTYCrg43tufdpvSQvNHMjj0V5nvfszAXMsNB/AmxtQ8ktvo PCfpS04Btz8RNaqdbwd2wJOJvaK32OPhaR9aXA08cbZF0uwlL5MjdRNHL/4pxdzPGBoA QCmXQO2maMxcZbMN2umR3p7rUWgGOgTprBScTJxrDNn/60wHYrmY9UDBS4YrQpVlN9Rh BTzA== 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=bOtt/hBntAv92axjJjSWGG95dNOUsappt5O5csvAlfM=; b=pq6WkuK4Rbk8HBG6hng0xb8ugQbKXqOsMzvzgzFG1mXhO3oIkuGtGJ3Xeux2G8qmnO EioPic3Fmy4gBfdpGVCA40V9UNg/9ExmCq4VMFZQjY6/QJLaPIp37XAC3d/lPEjxnN6z bnkgHOTwQ5tf6xmQL5FTKu8t6RzKz5VI4ycftVX1/mXH+w4RbVpwDIuvM4e45x2mQjdT iC8cPBhe/9Qq1UXuQiUprC1y+1eFqhbcbxwECpfZh7G6PnCU36ZDwUIwoExYBwq91bsw 4jHlySUHzLBh/zGWmeIk8TLo77rehVpYSBr4AAOfch7XKg3Bh12UY1AuNbCyrJ3AdHb0 2JkQ== 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=bOtt/hBntAv92axjJjSWGG95dNOUsappt5O5csvAlfM=; b=pXB5THWGU5loZBAc99d784HheK+v8mYViZvDt4KmPSGutca9etzNOcnG7l3mWVrx84 432DZdCsegobxhQ9xBEiCCh1T4Gqcpe5rQFOWWkRjtkPVCc05R6Qc2P8wr7UMxCqwGrG wjI65lbxU/O2cDIKz+ZbPt6zF+y2bqwBMn4GC0BCj7ypElzh5yeWBZoqreJo2aAdIG6r ZiOhZn1pQV+8F9P1GTECgYx8yt+N9b8H6xlfJdGrUr/nP8o7gPehb8q28JaLfQTRu27f +nwdSTIGBeZ/31mg73Ta/O9ajBDdjiXQ4yjrHH87WxVaQQNxch1/jD57qpgUVspsv4cp 9NqA== X-Gm-Message-State: AHQUAua5SDOa/8HsIXr15e6TsjFx1ibs0+CkiMJUEypWV1Jvq9ucN2Nv JhMe5ogoMe4qg/vOneT2aXzDFg== X-Google-Smtp-Source: AHgI3Ib1yG3cxzI8ZtzUnisRDzdPAgrj330m/J9nKpNDQ6GxZd6QuQmuX8L0i4qUf/mJFeaAVMgOyw== X-Received: by 2002:a25:6412:: with SMTP id y18mr18756725ybb.53.1550687320928; Wed, 20 Feb 2019 10:28:40 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a25:d58:: with SMTP id 85ls7063152ybn.8.gmail; Wed, 20 Feb 2019 10:28:39 -0800 (PST) X-Received: by 2002:a25:8042:: with SMTP id a2mr312314ybn.2.1550687319206; Wed, 20 Feb 2019 10:28:39 -0800 (PST) X-Original-Sender: kristen.wegner@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: 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:41478 Archived-At: ------=_Part_63_2021104249.1550687318711 Content-Type: multipart/alternative; boundary="----=_Part_64_400953254.1550687318711" ------=_Part_64_400953254.1550687318711 Content-Type: text/plain; charset="UTF-8" Hi. This is my first post here after lurking a while, so forgive me if I am barking up the wrong tree. I am contemplating how exceptions are represented, and whether they might be improved somehow. Exceptions are currently just structs or classes like any other, yet they are used quite differently. What if we had smarter "exception classes" that had a few specialized facilities for doing the things that exceptions need to do? We have "enum class," how about "exception class?" For example: #ifndef _EXCEPTION_CLASSES #define exception #endif exception class my_exception // 'exception class' gives us permission to override catch. { public: my_exception(const std::string& message, int thing) : message_(message), thing_(thing) { } void complain() const { std::cerr << "Caught '" << typeid(*this).name() << "': " << message_ << ", thing was: " << thing_ << std::endl; } #ifdef _EXCEPTION_CLASSES // Here we handle being caught. my_exception& operator catch() { complain(); return *this; } #endif private: std::string message_; int thing_; }; Now, when I do something like: int dummy(int thing) { try { if (!thing) throw my_exception("Dummy: Bad thing", thing); } catch(my_exception& e) // my_exception::operator catch() gets called. { #ifndef _EXCEPTION_CLASSES e.complain(); // Not needed with exception classes. #endif } } .... I automatically get called when my exception class is caught. Presto, I can override operator catch() in all of my exceptions and enable automatic tracing. Are there any more ideas out there how to improve exceptions? -- 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 email 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/518a0db5-b7f2-470f-b0be-606f66f1c786%40isocpp.org. ------=_Part_64_400953254.1550687318711 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi. This is my first post here after lurking a while, so f= orgive me if I am barking up the wrong tree.

I am contem= plating how exceptions are represented, and whether they might be improved = somehow. Exceptions are currently just structs or classes like any other, y= et they are used quite differently.

What if we had= smarter "exception classes" that had a few specialized facilitie= s for doing the things that exceptions need to do? We have "enum class," how about "exception class?" For example:<= /div>

#ifndef _EXCEPTION_CLASSES
=
#define=C2=A0exception=C2=A0
#endif

=
exception class my_exception=C2=A0//= =C2=A0'exception=C2=A0class' g= iv<= /span>es us permission to override catch.
{
public:
my_exception(const std::string&a= mp; message, int thing) : message_(message),= thing_(thing) { }
void complain() const {
<= font face=3D"courier new, monospace">
= std::cerr << "Caught '" << typeid(*this).= name() << "': " << message_ << ", thin= g was: " << thing_ << std::endl;
}
#ifdef _EXCEPT= ION_CLASSES
// Her= e we handle being caught.
my_exception& operator catch() {
compla= in();
return *this;
}
#endif
private:
std::strin= g message_;
int thing_;<= /font>
};

Now, when I do something like:

int dummy(int thing)
{
try
{
if (!thing) throw my_exception= ("Dummy: Bad thing", thing);
}
<= /span>catch(my_exception& e) // my_exception::operator catch() gets called.
{
#ifndef _EXCEPTION_CLASSES
e.complai= n(); // Not needed with exception classes.
#endif
}
}
=C2=A0
... I automatically g= et called when my exception class is caught. Presto, I can override operator catch() in all of my excepti= ons and enable automatic tracing.

Are there any mo= re ideas out there how to improve exceptions?

--
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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/518a0db5-b7f2-470f-b0be-606f66f1c786= %40isocpp.org.
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