digitalmars.D.learn - DMD OSX / Segfault 11
- =?iso-8859-1?Q?Robert_M._M=FCnch?= (17/17) Feb 02 2016 I have a very strange effect, I'm not sure what it is about:
- Steven Schveighoffer (3/16) Feb 02 2016 If this is valid D, I'm not sure what it means :)
- =?iso-8859-1?Q?Robert_M._M=FCnch?= (7/8) Feb 03 2016 There was one type, the rest I stripped totally away as IMO it's not
- Steven Schveighoffer (3/7) Feb 03 2016 Very relevant: what are you declaring? A class, struct, template, enum?
- =?iso-8859-1?Q?Robert_M._M=FCnch?= (6/16) Feb 04 2016 ;-) Ok... that's really missing. A class.
- anonymous (12/24) Feb 02 2016 This isn't valid D code at all, which makes it unnecessarily hard to
- =?iso-8859-1?Q?Robert_M._M=FCnch?= (12/24) Feb 03 2016 Well, it should of course be:
- anonymous (9/22) Feb 03 2016 Still missing "class". I know I'm being pedantic, but if you're being
- =?iso-8859-1?Q?Robert_M._M=FCnch?= (11/27) Feb 04 2016 Aha, that's my missing link. I didn't know that and it makes it all clea...
I have a very strange effect, I'm not sure what it is about:
Value: {}
WordV: Value {
Value* get() {}
}
BaseOperator: Value : {
}
Now comes the code using this:
auto op = cast(BaseOperator)(Word.get());
if (op !is null) {...
If get() returns "Value*" it segfaults, if I change it to "Value" it
works. How can this be?
I want to check of the Value returned from get() is a BaseOperator or not.
--
Robert M. Münch
http://www.saphirion.com
smarter | better | faster
Feb 02 2016
On 2/2/16 1:06 PM, Robert M. Münch wrote:
I have a very strange effect, I'm not sure what it is about:
Value: {}
WordV: Value {
Value* get() {}
}
BaseOperator: Value : {
}
Now comes the code using this:
auto op = cast(BaseOperator)(Word.get());
if (op !is null) {...
If get() returns "Value*" it segfaults, if I change it to "Value" it
works. How can this be?
I want to check of the Value returned from get() is a BaseOperator or not.
If this is valid D, I'm not sure what it means :)
-Steve
Feb 02 2016
On 2016-02-02 18:59:35 +0000, Steven Schveighoffer said:If this is valid D, I'm not sure what it means :)There was one type, the rest I stripped totally away as IMO it's not relevant for the actual problem. -- Robert M. Münch http://www.saphirion.com smarter | better | faster
Feb 03 2016
On 2/3/16 8:17 AM, Robert M. Münch wrote:On 2016-02-02 18:59:35 +0000, Steven Schveighoffer said:Very relevant: what are you declaring? A class, struct, template, enum? -SteveIf this is valid D, I'm not sure what it means :)There was one type, the rest I stripped totally away as IMO it's not relevant for the actual problem.
Feb 03 2016
=?iso-8859-1?Q?Robert_M._M=FCnch?= <robert.muench saphirion.com> On 2016-02-03 14:35:16 +0000, Steven Schveighoffer said:On 2/3/16 8:17 AM, Robert M. Münch wrote:;-) Ok... that's really missing. A class. -- Robert M. Münch http://www.saphirion.com smarter | better | fasterOn 2016-02-02 18:59:35 +0000, Steven Schveighoffer said:Very relevant: what are you declaring? A class, struct, template, enum?If this is valid D, I'm not sure what it means :)There was one type, the rest I stripped totally away as IMO it's not relevant for the actual problem.
Feb 04 2016
On 02.02.2016 19:06, Robert M. Münch wrote:I have a very strange effect, I'm not sure what it is about: Value: {} WordV: Value { Value* get() {} } BaseOperator: Value : { }This isn't valid D code at all, which makes it unnecessarily hard to understand what you mean.Now comes the code using this: auto op = cast(BaseOperator)(Word.get()); if (op !is null) {... If get() returns "Value*" it segfaults, if I change it to "Value" it works. How can this be?A Value* is a pointer to a class reference. Unless you're doing something really funky with the pointer, casting it to a class type doesn't make sense. Casting between class types that have an inheritance relation, like Value and BaseOperator, does make sense (upcat/downcast). If anything, you should be casting between Value* and BaseOperator* (both pointer types) if you want to do something with pointers. But you very seldom need pointers to class references. Just return Value from get, and cast to BaseOperator.
Feb 02 2016
On 2016-02-02 19:03:04 +0000, anonymous said:This isn't valid D code at all, which makes it unnecessarily hard to understand what you mean.Well, it should of course be: BaseOperator: Value { }A Value* is a pointer to a class reference. Unless you're doing something really funky with the pointer, casting it to a class type doesn't make sense. Casting between class types that have an inheritance relation, like Value and BaseOperator, does make sense (upcat/downcast).Yes, that's what I need.If anything, you should be casting between Value* and BaseOperator* (both pointer types) if you want to do something with pointers.I tried this, but that doesn't work either.But you very seldom need pointers to class references. Just return Value from get, and cast to BaseOperator.But am I not getting a copy then? I want to avoid copying objects as much as possible. -- Robert M. Münch http://www.saphirion.com smarter | better | faster
Feb 03 2016
On 03.02.2016 14:16, Robert M. Münch wrote:Well, it should of course be: BaseOperator: Value { }Still missing "class". I know I'm being pedantic, but if you're being sloppy here, how do I know that you're not being sloppy where it matters?Do that then. Cast between class types. Pointers don't by you anything here.Casting between class types that have an inheritance relation, like Value and BaseOperator, does make sense (upcat/downcast).Yes, that's what I need.Yeah, you can't check if the downcast succeeded this way. Casts between pointers always succeed (and then fail horribly at run-time).If anything, you should be casting between Value* and BaseOperator* (both pointer types) if you want to do something with pointers.I tried this, but that doesn't work either.No, you're not getting a copy. Classes are reference types. That means, variables of class types are references already. They're pointers in disguise.But you very seldom need pointers to class references. Just return Value from get, and cast to BaseOperator.But am I not getting a copy then? I want to avoid copying objects as much as possible.
Feb 03 2016
On 2016-02-03 13:29:15 +0000, anonymous said:Still missing "class". I know I'm being pedantic, but if you're being sloppy here, how do I know that you're not being sloppy where it matters?You are right, sorry. I was to focused on the problem part...Aha, that's my missing link. I didn't know that and it makes it all clear. IMO that's a not to underestimate trap. Since I can use the . notation instead of -> when using pointers, I would have expected that casting will work the same with both variants as well...Yeah, you can't check if the downcast succeeded this way. Casts between pointers always succeed (and then fail horribly at run-time).If anything, you should be casting between Value* and BaseOperator* (both pointer types) if you want to do something with pointers.I tried this, but that doesn't work either.Ok. Seems I was really confused. Thanks a lot. -- Robert M. Münch http://www.saphirion.com smarter | better | fasterBut am I not getting a copy then? I want to avoid copying objects as much as possible.No, you're not getting a copy. Classes are reference types. That means, variables of class types are references already. They're pointers in disguise.
Feb 04 2016