digitalmars.D - Navigate from ClassInfo to TypeInfo

Frank Benoit (6/6) Apr 14 2009 I need to retrieve an instance of TypeInfo from an object instance at

Christopher Wright (7/16) Apr 14 2009 There is no way that I know of to do so, and I've looked into the issue

Tomas Lindquist Olsen (2/18) Apr 14 2009 Seems reasonable to me to add a TypeInfo field to ClassInfo.

davidl (6/12) Apr 14 2009 Send this object to vararg func, and retrieve the TypeInfo there and

Jarrett Billingsley (2/3) Apr 14 2009 No. The typeinfo passed to vararg functions is also determined at compi...

davidl (6/12) Apr 14 2009 so it's a bug?

Daniel Keep (6/29) Apr 14 2009 bar cannot possibly know what the "real" TypeInfo of a is. But that

Frank Benoit (3/37) Apr 14 2009 Or it can request the classinfo of the passed object. Hey, and now the

Daniel Keep (11/46) Apr 14 2009 Ok. What do you propose to do with this TypeInfo?

Frank Benoit (8/21) Apr 14 2009 I need to have a "something" to retrieve and pass around to hold all

Daniel Keep (6/40) Apr 14 2009 I remember having to do something similar once. I think I solved it by

Frank Benoit (4/51) Apr 15 2009 Ick! Right, that is doable.

Steven Schveighoffer (27/48) Apr 15 2009 Frank, Daniel is right, TypeInfo_Class simply adds a classinfo member. ...

davidl (7/39) Apr 16 2009 If the caller only sends the object typeinfo, then the vararg typeinfo i...

Fawzi Mohamed (4/49) Apr 16 2009 For people interested in runtime introspection tango.core.RuntimeTraits

Frank Benoit (2/7) Apr 16 2009 After the next tango release :)

Frank Benoit (3/12) Apr 15 2009 See also:
grauzone (5/14) Apr 15 2009 I also did hit this issue. Fortunately, I never get a ClassInfo of a

Frank Benoit <keinfarbton googlemail.com> writes:

I need to retrieve an instance of TypeInfo from an object instance at
runtime.

TypeInfo info = typeid(obj) // does not work, only compile time

TypeInfo info = obj.classinfo.????; // how to navigate to TypeInfo?

Is that possible?
If not, why? And can it be added (D1)?

Apr 14 2009

Christopher Wright <dhasenan gmail.com> writes:

Frank Benoit wrote:
 I need to retrieve an instance of TypeInfo from an object instance at
 runtime.
 
 TypeInfo info = typeid(obj) // does not work, only compile time
 
 TypeInfo info = obj.classinfo.????; // how to navigate to TypeInfo?
 
 Is that possible?
 If not, why? And can it be added (D1)?

There is no way that I know of to do so, and I've looked into the issue 
previously. -- I don't know how TypeInfo is instantiated; I imagine it's 
in the data segment of the executable; so it should be possible to 
examine all symbols in an executable to find TypeInfo instances and 
determine what they refer to. However, the language and runtime lack 
support for this.

Apr 14 2009

Tomas Lindquist Olsen <tomas.l.olsen gmail.com> writes:

On Wed, Apr 15, 2009 at 1:35 AM, Christopher Wright <dhasenan gmail.com> wrote:
 Frank Benoit wrote:
 I need to retrieve an instance of TypeInfo from an object instance at
 runtime.

 TypeInfo info = typeid(obj) // does not work, only compile time

 TypeInfo info = obj.classinfo.????; // how to navigate to TypeInfo?

 Is that possible?
 If not, why? And can it be added (D1)?

 There is no way that I know of to do so, and I've looked into the issue
 previously. -- I don't know how TypeInfo is instantiated; I imagine it's in
 the data segment of the executable; so it should be possible to examine all
 symbols in an executable to find TypeInfo instances and determine what they
 refer to. However, the language and runtime lack support for this.

Seems reasonable to me to add a TypeInfo field to ClassInfo.

Apr 14 2009

davidl <davidl nospam.org> writes:

�� Wed, 15 Apr 2009 02:16:44 +0800��Frank Benoit  
<keinfarbton googlemail.com> д��:

 I need to retrieve an instance of TypeInfo from an object instance at
 runtime.

 TypeInfo info = typeid(obj) // does not work, only compile time

 TypeInfo info = obj.classinfo.????; // how to navigate to TypeInfo?

 Is that possible?
 If not, why? And can it be added (D1)?

Send this object to vararg func, and retrieve the TypeInfo there and  
return?

-- 
ʹ�� Opera �����Եĵ����ʼ��ͻ�����: http://www.opera.com/mail/

Apr 14 2009

Jarrett Billingsley <jarrett.billingsley gmail.com> writes:

2009/4/14 davidl <davidl nospam.org>:
 Send this object to vararg func, and retrieve the TypeInfo there and return?

No.  The typeinfo passed to vararg functions is also determined at compile-time.

Apr 14 2009

davidl <davidl nospam.org> writes:

�� Wed, 15 Apr 2009 10:14:42 +0800��Jarrett Billingsley  
<jarrett.billingsley gmail.com> д��:

 2009/4/14 davidl <davidl nospam.org>:
 Send this object to vararg func, and retrieve the TypeInfo there and  
 return?

 No.  The typeinfo passed to vararg functions is also determined at  
 compile-time.

so it's a bug?

I think vararg funcs always want the real typeinfo of the object

-- 
ʹ�� Opera �����Եĵ����ʼ��ͻ�����: http://www.opera.com/mail/

Apr 14 2009

Daniel Keep <daniel.keep.lists gmail.com> writes:

davidl wrote:
 �� Wed, 15 Apr 2009 10:14:42 +0800��Jarrett Billingsley
 <jarrett.billingsley gmail.com> д��:
 
 2009/4/14 davidl <davidl nospam.org>:
 Send this object to vararg func, and retrieve the TypeInfo there and
 return?

 No.  The typeinfo passed to vararg functions is also determined at
 compile-time.

 
 so it's a bug?
 
 I think vararg funcs always want the real typeinfo of the object

No, they get the typeinfo of what they're passed.

 class A {}
 class B : A {}

 void foo(...) {}

 void bar(A a) { foo(a); }

 void main()
 {
     scope b = new B;
     bar(b);
 }

bar cannot possibly know what the "real" TypeInfo of a is.  But that
doesn't matter because it's passing an A with A's TypeInfo.  And if foo
is maybe interested in Bs, then it can just try to up-cast.

  -- Daniel

Apr 14 2009

Frank Benoit <keinfarbton googlemail.com> writes:

Daniel Keep schrieb:
 
 davidl wrote:
 在 Wed, 15 Apr 2009 10:14:42 +0800，Jarrett Billingsley
 <jarrett.billingsley gmail.com> 写道:

 2009/4/14 davidl <davidl nospam.org>:
 Send this object to vararg func, and retrieve the TypeInfo there and
 return?

 No.  The typeinfo passed to vararg functions is also determined at
 compile-time.

 so it's a bug?

 I think vararg funcs always want the real typeinfo of the object

 
 No, they get the typeinfo of what they're passed.
 
 class A {}
 class B : A {}

 void foo(...) {}

 void bar(A a) { foo(a); }

 void main()
 {
     scope b = new B;
     bar(b);
 }

 
 bar cannot possibly know what the "real" TypeInfo of a is.  But that
 doesn't matter because it's passing an A with A's TypeInfo.  And if foo
 is maybe interested in Bs, then it can just try to up-cast.
 
   -- Daniel

Or it can request the classinfo of the passed object. Hey, and now the
typeinfo please :)

Apr 14 2009

Daniel Keep <daniel.keep.lists gmail.com> writes:

Frank Benoit wrote:
 Daniel Keep schrieb:
 davidl wrote:
 在 Wed, 15 Apr 2009 10:14:42 +0800，Jarrett Billingsley
 <jarrett.billingsley gmail.com> 写道:

 2009/4/14 davidl <davidl nospam.org>:
 Send this object to vararg func, and retrieve the TypeInfo there and
 return?

 No.  The typeinfo passed to vararg functions is also determined at
 compile-time.

 so it's a bug?

 I think vararg funcs always want the real typeinfo of the object

 No, they get the typeinfo of what they're passed.

 class A {}
 class B : A {}

 void foo(...) {}

 void bar(A a) { foo(a); }

 void main()
 {
     scope b = new B;
     bar(b);
 }

 bar cannot possibly know what the "real" TypeInfo of a is.  But that
 doesn't matter because it's passing an A with A's TypeInfo.  And if foo
 is maybe interested in Bs, then it can just try to up-cast.

   -- Daniel

 
 Or it can request the classinfo of the passed object. Hey, and now the
 typeinfo please :)

Ok.  What do you propose to do with this TypeInfo?

The ONLY thing a given TypeInfo_Class gives you is the ClassInfo, which
you already have.  The TypeInfo object itself gives you getHash, equals
and compare, all of which are in Object and thus redundant, tsize which
is the size of a pointer, swap which I can't see a use for, next which
is useless, init which is also redundant and flags which is already in
ClassInfo.

Again, why do you even want that specific TypeInfo when it is less
useful than the ClassInfo?

  -- Daniel

Apr 14 2009

Frank Benoit <keinfarbton googlemail.com> writes:

Daniel Keep schrieb:
 Ok.  What do you propose to do with this TypeInfo?
 
 The ONLY thing a given TypeInfo_Class gives you is the ClassInfo, which
 you already have.  The TypeInfo object itself gives you getHash, equals
 and compare, all of which are in Object and thus redundant, tsize which
 is the size of a pointer, swap which I can't see a use for, next which
 is useless, init which is also redundant and flags which is already in
 ClassInfo.
 
 Again, why do you even want that specific TypeInfo when it is less
 useful than the ClassInfo?
 
   -- Daniel

I need to have a "something" to retrieve and pass around to hold all
available information about a type. Including classes, interfaces and
primitives.
Because of ClassInfo cannot have information about primitives, I need to
work with TypeInfo.
Because of I have that need to retrieve that "something" from any object
reference also, i need a way from classinfo to typeinfo.

Apr 14 2009

Daniel Keep <daniel.keep.lists gmail.com> writes:

Frank Benoit wrote:
 Daniel Keep schrieb:
 Ok.  What do you propose to do with this TypeInfo?

 The ONLY thing a given TypeInfo_Class gives you is the ClassInfo, which
 you already have.  The TypeInfo object itself gives you getHash, equals
 and compare, all of which are in Object and thus redundant, tsize which
 is the size of a pointer, swap which I can't see a use for, next which
 is useless, init which is also redundant and flags which is already in
 ClassInfo.

 Again, why do you even want that specific TypeInfo when it is less
 useful than the ClassInfo?

   -- Daniel

 
 I need to have a "something" to retrieve and pass around to hold all
 available information about a type. Including classes, interfaces and
 primitives.
 Because of ClassInfo cannot have information about primitives, I need to
 work with TypeInfo.
 Because of I have that need to retrieve that "something" from any object
 reference also, i need a way from classinfo to typeinfo.
 

I remember having to do something similar once.  I think I solved it by
carrying around these:

 struct ExTypeInfo
 {
     TypeInfo ti;
     ClassInfo ci;
 }

That, or you could store them as Objects, and then use upcasts to work
out which it is.

 if( auto ti = cast(TypeInfo) info )
     // It's a general type info

 else if( auto ci = cast(ClassInfo) info )
     // It's a class

 else
     assert(false);

  -- Daniel

Apr 14 2009

Frank Benoit <keinfarbton googlemail.com> writes:

Daniel Keep schrieb:
 
 Frank Benoit wrote:
 Daniel Keep schrieb:
 Ok.  What do you propose to do with this TypeInfo?

 The ONLY thing a given TypeInfo_Class gives you is the ClassInfo, which
 you already have.  The TypeInfo object itself gives you getHash, equals
 and compare, all of which are in Object and thus redundant, tsize which
 is the size of a pointer, swap which I can't see a use for, next which
 is useless, init which is also redundant and flags which is already in
 ClassInfo.

 Again, why do you even want that specific TypeInfo when it is less
 useful than the ClassInfo?

   -- Daniel

 I need to have a "something" to retrieve and pass around to hold all
 available information about a type. Including classes, interfaces and
 primitives.
 Because of ClassInfo cannot have information about primitives, I need to
 work with TypeInfo.
 Because of I have that need to retrieve that "something" from any object
 reference also, i need a way from classinfo to typeinfo.

 
 I remember having to do something similar once.  I think I solved it by
 carrying around these:
 
 struct ExTypeInfo
 {
     TypeInfo ti;
     ClassInfo ci;
 }

 
 That, or you could store them as Objects, and then use upcasts to work
 out which it is.
 
 if( auto ti = cast(TypeInfo) info )
     // It's a general type info

 else if( auto ci = cast(ClassInfo) info )
     // It's a class

 else
     assert(false);

 
   -- Daniel

Ick! Right, that is doable.
But still, D lacks this navigation and it should be added.
Working with Object is really the ugly way.

Apr 15 2009

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Wed, 15 Apr 2009 02:41:50 -0400, Frank Benoit  
<keinfarbton googlemail.com> wrote:

 Daniel Keep schrieb:
 Ok.  What do you propose to do with this TypeInfo?

 The ONLY thing a given TypeInfo_Class gives you is the ClassInfo, which
 you already have.  The TypeInfo object itself gives you getHash, equals
 and compare, all of which are in Object and thus redundant, tsize which
 is the size of a pointer, swap which I can't see a use for, next which
 is useless, init which is also redundant and flags which is already in
 ClassInfo.

 Again, why do you even want that specific TypeInfo when it is less
 useful than the ClassInfo?

   -- Daniel

 I need to have a "something" to retrieve and pass around to hold all
 available information about a type. Including classes, interfaces and
 primitives.
 Because of ClassInfo cannot have information about primitives, I need to
 work with TypeInfo.
 Because of I have that need to retrieve that "something" from any object
 reference also, i need a way from classinfo to typeinfo.


Frank, Daniel is right, TypeInfo_Class simply adds a classinfo member.   
Each class type does not use a different TypeInfo derivative, it simply  
uses a different *instance*.  For everything that doesn't use the  
classinfo member in TypeInfo_Class, you can use Object's typeinfo, which  
should be accurate.

For everything else, use the classinfo.

Functions that you can use from Object's typeinfo:

getHash
equals
compare
tsize
flags
swap
next
init


Functions that use classinfo:

offTi
toString
opCmp
opEquals

Which you can simply call classinfo's appropriate functions.

You can also easily build a TypeInfo_Class based on the object:

scope info = new TypeInfo_Class();
info.info = obj.classinfo;

-Steve

Apr 15 2009

davidl <davidl nospam.org> writes:

�� Wed, 15 Apr 2009 13:56:20 +0800��Daniel Keep  
<daniel.keep.lists gmail.com> д��:

 davidl wrote:
 �� Wed, 15 Apr 2009 10:14:42 +0800��Jarrett Billingsley
 <jarrett.billingsley gmail.com> д��:

 2009/4/14 davidl <davidl nospam.org>:
 Send this object to vararg func, and retrieve the TypeInfo there and
 return?

 No.  The typeinfo passed to vararg functions is also determined at
 compile-time.

 so it's a bug?

 I think vararg funcs always want the real typeinfo of the object

 No, they get the typeinfo of what they're passed.

 class A {}
 class B : A {}

 void foo(...) {}

 void bar(A a) { foo(a); }

 void main()
 {
     scope b = new B;
     bar(b);
 }

 bar cannot possibly know what the "real" TypeInfo of a is.  But that
 doesn't matter because it's passing an A with A's TypeInfo.  And if foo
 is maybe interested in Bs, then it can just try to up-cast.

   -- Daniel

If the caller only sends the object typeinfo, then the vararg typeinfo is  
so limited to be valid for primitives. It's definitely useless for classes  
cases.

-- 
ʹ�� Opera �����Եĵ����ʼ��ͻ�����: http://www.opera.com/mail/

Apr 16 2009

Fawzi Mohamed <fmohamed mac.com> writes:

On 2009-04-16 12:18:31 +0200, davidl <davidl nospam.org> said:

 在 Wed, 15 Apr 2009 13:56:20 +0800，Daniel Keep  
 <daniel.keep.lists gmail.com> 写道:
 
 
 
 davidl wrote:
 在 Wed, 15 Apr 2009 10:14:42 +0800，Jarrett Billingsley
 <jarrett.billingsley gmail.com> 写道:
 
 2009/4/14 davidl <davidl nospam.org>:
 
 Send this object to vararg func, and retrieve the TypeInfo there and
 return?

 
 No.  The typeinfo passed to vararg functions is also determined at
 compile-time.

 
 so it's a bug?
 
 I think vararg funcs always want the real typeinfo of the object

 
 No, they get the typeinfo of what they're passed.
 
 class A {}
 class B : A {}
 
 void foo(...) {}
 
 void bar(A a) { foo(a); }
 
 void main()
 {
     scope b = new B;
     bar(b);
 }

 
 bar cannot possibly know what the "real" TypeInfo of a is.  But that
 doesn't matter because it's passing an A with A's TypeInfo.  And if foo
 is maybe interested in Bs, then it can just try to up-cast.
 
   -- Daniel

 
 If the caller only sends the object typeinfo, then the vararg typeinfo 
 is  so limited to be valid for primitives. It's definitely useless for 
 classes  cases.

For people interested in runtime introspection tango.core.RuntimeTraits 
might be interesting.

Fawzi

Apr 16 2009

Frank Benoit <keinfarbton googlemail.com> writes:

Fawzi Mohamed schrieb:

 For people interested in runtime introspection tango.core.RuntimeTraits
 might be interesting.
 
 Fawzi
 

After the next tango release :)

Apr 16 2009

Frank Benoit <keinfarbton googlemail.com> writes:

Frank Benoit schrieb:
 I need to retrieve an instance of TypeInfo from an object instance at
 runtime.
 
 TypeInfo info = typeid(obj) // does not work, only compile time
 
 TypeInfo info = obj.classinfo.????; // how to navigate to TypeInfo?
 
 Is that possible?
 If not, why? And can it be added (D1)?

See also:
http://d.puremagic.com/issues/show_bug.cgi?id=2836

Apr 15 2009

grauzone <none example.net> writes:

Frank Benoit wrote:
 I need to retrieve an instance of TypeInfo from an object instance at
 runtime.
 
 TypeInfo info = typeid(obj) // does not work, only compile time
 
 TypeInfo info = obj.classinfo.????; // how to navigate to TypeInfo?
 
 Is that possible?
 If not, why? And can it be added (D1)?

I also did hit this issue. Fortunately, I never get a ClassInfo of a 
class whose static type I didn't see at least once before. This means I 
can get both the TypeInfo and ClassInfo from the static type, and put 
them into a global AA like ClassInfo[TypeInfo].

Apr 15 2009

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