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digitalmars.D - Throwable, Exception, and Error

reply Steve Teale <steve.teale britseyeview.com> writes:
If I want a catch-all catch, which should I be using.

Out of habit I use Exception, but if I do that then I will miss some things
thrown from Phobos.

Is it the intention that Throwable be used for this purpose?
May 01 2009
parent reply Walter Bright <newshound1 digitalmars.com> writes:
Steve Teale wrote:
 If I want a catch-all catch, which should I be using.
 
 Out of habit I use Exception, but if I do that then I will miss some things
thrown from Phobos.
 
 Is it the intention that Throwable be used for this purpose?
 

Yes.
May 02 2009
next sibling parent reply Frank Benoit <keinfarbton googlemail.com> writes:
Walter Bright schrieb:
 Steve Teale wrote:
 If I want a catch-all catch, which should I be using.

 Out of habit I use Exception, but if I do that then I will miss some
 things thrown from Phobos.

 Is it the intention that Throwable be used for this purpose?

Yes.

Why is it possible to throw an Object? I think "throw" and "catch" should be restricted to Throwable and derived types.
May 02 2009
parent reply Christopher Wright <dhasenan gmail.com> writes:
Frank Benoit wrote:
 Walter Bright schrieb:
 Steve Teale wrote:
 If I want a catch-all catch, which should I be using.

 Out of habit I use Exception, but if I do that then I will miss some
 things thrown from Phobos.

 Is it the intention that Throwable be used for this purpose?


Why is it possible to throw an Object? I think "throw" and "catch" should be restricted to Throwable and derived types.

Because Phobos did not contain Throwable until the advent of druntime. This was sufficiently recent that Walter has not yet modified the compiler accordingly, or, most likely, noticed or decided to do so.
May 03 2009
parent reply Steve Teale <steve.teale britseyeview.com> writes:
Christopher Wright Wrote:

 Frank Benoit wrote:
 Walter Bright schrieb:
 Steve Teale wrote:
 If I want a catch-all catch, which should I be using.

 Out of habit I use Exception, but if I do that then I will miss some
 things thrown from Phobos.

 Is it the intention that Throwable be used for this purpose?


Why is it possible to throw an Object? I think "throw" and "catch" should be restricted to Throwable and derived types.

Because Phobos did not contain Throwable until the advent of druntime. This was sufficiently recent that Walter has not yet modified the compiler accordingly, or, most likely, noticed or decided to do so.

When that is done, and the object being thrown has been checked out, would it be a good idea for the compiler to automatically populate the file and line members of the Throwable?
May 03 2009
parent reply Christopher Wright <dhasenan gmail.com> writes:
Steve Teale wrote:
 Christopher Wright Wrote:
 
 Frank Benoit wrote:
 Walter Bright schrieb:
 Steve Teale wrote:
 If I want a catch-all catch, which should I be using.

 Out of habit I use Exception, but if I do that then I will miss some
 things thrown from Phobos.

 Is it the intention that Throwable be used for this purpose?


I think "throw" and "catch" should be restricted to Throwable and derived types.

This was sufficiently recent that Walter has not yet modified the compiler accordingly, or, most likely, noticed or decided to do so.

When that is done, and the object being thrown has been checked out, would it be a good idea for the compiler to automatically populate the file and line members of the Throwable?

Hrm. You want to assign the file and line numbers where the exception is thrown, but not if you are rethrowing the exception. The runtime has something like _d_throw; if the signature included __FILE__ and __LINE__ for the throw expression, that should work.
May 03 2009
parent reply Steve Teale <steve.teale britseyeview.com> writes:
Christopher Wright Wrote:

 Steve Teale wrote:
 Christopher Wright Wrote:
 
 Frank Benoit wrote:
 Walter Bright schrieb:
 Steve Teale wrote:
 If I want a catch-all catch, which should I be using.

 Out of habit I use Exception, but if I do that then I will miss some
 things thrown from Phobos.

 Is it the intention that Throwable be used for this purpose?


I think "throw" and "catch" should be restricted to Throwable and derived types.

This was sufficiently recent that Walter has not yet modified the compiler accordingly, or, most likely, noticed or decided to do so.

When that is done, and the object being thrown has been checked out, would it be a good idea for the compiler to automatically populate the file and line members of the Throwable?

Hrm. You want to assign the file and line numbers where the exception is thrown, but not if you are rethrowing the exception. The runtime has something like _d_throw; if the signature included __FILE__ and __LINE__ for the throw expression, that should work.

OK, I did not think it through, but it would save a lot of typing grief; ... , __FILE__, __LINE__); every time you wanted to be careful.
May 03 2009
parent Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
Jarrett Billingsley wrote:
 On Sun, May 3, 2009 at 4:14 PM, Denis Koroskin <2korden gmail.com> wrote:
 PHP allows function definition like this:

 void foo(Args args, string fileName = __FILE__, int line = __LINE__)
 {
  // do stuff
 }

Hidden feature: D2 allows it too, at least with templates. void Throw(T : Throwable, string file = __FILE__, int line = __LINE__)(T ex) { ex.file = file; ex.line = line; throw ex; } void foobar() { Throw(new Exception("o hai")); } void main() { try foobar(); catch(RangeError e) writefln("(%s: %d) %s", e.file, e.line, e.msg); } I did find a sort of bug when trying a slightly different implementation of this though - any kind of explicit instantiation of the Throw template causes the __FILE__ and __LINE__ to be evaluated in the scope of the template rather than at the call site.

That's intentional and is used in enforce() and a couple other places in Phobos. Andrei
May 03 2009
prev sibling next sibling parent "Denis Koroskin" <2korden gmail.com> writes:
On Sun, 03 May 2009 09:57:02 +0400, Frank Benoit <keinfarbton googlemail.com>
wrote:

 Walter Bright schrieb:
 Steve Teale wrote:
 If I want a catch-all catch, which should I be using.

 Out of habit I use Exception, but if I do that then I will miss some
 things thrown from Phobos.

 Is it the intention that Throwable be used for this purpose?

Yes.

Why is it possible to throw an Object? I think "throw" and "catch" should be restricted to Throwable and derived types.

This is going to be addressed, so no worries.
May 03 2009
prev sibling next sibling parent "Denis Koroskin" <2korden gmail.com> writes:
On Sun, 03 May 2009 22:12:00 +0400, Steve Teale <steve.teale britseyeview.com>
wrote:

 Christopher Wright Wrote:

 Steve Teale wrote:
 Christopher Wright Wrote:

 Frank Benoit wrote:
 Walter Bright schrieb:
 Steve Teale wrote:
 If I want a catch-all catch, which should I be using.

 Out of habit I use Exception, but if I do that then I will miss  





 things thrown from Phobos.

 Is it the intention that Throwable be used for this purpose?


I think "throw" and "catch" should be restricted to Throwable and derived types.



 This was sufficiently recent that Walter has not yet modified the
 compiler accordingly, or, most likely, noticed or decided to do so.

When that is done, and the object being thrown has been checked out,

file and line members of the Throwable? Hrm. You want to assign the file and line numbers where the exception is thrown, but not if you are rethrowing the exception. The runtime has something like _d_throw; if the signature included __FILE__ and __LINE__ for the throw expression, that should work.

OK, I did not think it through, but it would save a lot of typing grief; ... , __FILE__, __LINE__); every time you wanted to be careful.

PHP allows function definition like this: void foo(Args args, string fileName = __FILE__, int line = __LINE__) { // do stuff } You call it like this: "foo(args);" and correct file name and line number is passed, i.e. default arguments are evaluated at call site. Can we use the same trick for exceptions? Here is an example: class Throwable { this(string fileName = __FILE__, int line = __LINE__) { ... } } class Exception : Throwable { this(string reason, string fileName = __FILE__, int line = __LINE__) { super(fileName, line); // ... } }
May 03 2009
prev sibling next sibling parent Jarrett Billingsley <jarrett.billingsley gmail.com> writes:
On Sun, May 3, 2009 at 4:14 PM, Denis Koroskin <2korden gmail.com> wrote:
 PHP allows function definition like this:

 void foo(Args args, string fileName =3D __FILE__, int line =3D __LINE__)
 {
 =A0// do stuff
 }

Hidden feature: D2 allows it too, at least with templates. void Throw(T : Throwable, string file =3D __FILE__, int line =3D __LINE__)(= T ex) { ex.file =3D file; ex.line =3D line; throw ex; } void foobar() { Throw(new Exception("o hai")); } void main() { try foobar(); catch(RangeError e) writefln("(%s: %d) %s", e.file, e.line, e.msg); } I did find a sort of bug when trying a slightly different implementation of this though - any kind of explicit instantiation of the Throw template causes the __FILE__ and __LINE__ to be evaluated in the scope of the template rather than at the call site.
May 03 2009
prev sibling next sibling parent Jarrett Billingsley <jarrett.billingsley gmail.com> writes:
On Sun, May 3, 2009 at 4:36 PM, Jarrett Billingsley
<jarrett.billingsley gmail.com> wrote:

 =A0 =A0 =A0 =A0catch(RangeError e)

eh that's supposed to be Exception
May 03 2009
prev sibling parent Jarrett Billingsley <jarrett.billingsley gmail.com> writes:
On Sun, May 3, 2009 at 5:07 PM, Andrei Alexandrescu
<SeeWebsiteForEmail erdani.org> wrote:

 I did find a sort of bug when trying a slightly different
 implementation of this though - any kind of explicit instantiation of
 the Throw template causes the __FILE__ and __LINE__ to be evaluated in
 the scope of the template rather than at the call site.

That's intentional and is used in enforce() and a couple other places in Phobos.

That's what I figured. It wasn't until I looked at the source to std.contracts that I found out about it, though, and I doubt many other people know about it. The only mention about it in the changelog is for 2.013, where it says "Changed __FILE__ and __LINE__ so they work as parameter default initializers" but that doesn't.. well, doesn't say a lot :P In any case, I doubt the bug is intentional.
May 03 2009