www.digitalmars.com         C & C++   DMDScript  

digitalmars.D - Get address of overloaded function

reply "Frank Benoit (keinfarbton)" <benoit tionex.removethispart.de> writes:
I want to assign a function ptr to a void* variable.

There are no compile error in case the function is a overloaded one. Is
this a bug?

How to select the correct function? I tried a cast, and it seams to work.

void fnc(){}
void fnc(int a ){}

void * ptr = cast(void*)cast( void function( int )) & fnc;
Feb 24 2007
parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Frank Benoit (keinfarbton)" <benoit tionex.removethispart.de> wrote in 
message news:erpk4o$1oom$1 digitalmars.com...
I want to assign a function ptr to a void* variable.

 There are no compile error in case the function is a overloaded one. Is
 this a bug?

 How to select the correct function? I tried a cast, and it seams to work.

 void fnc(){}
 void fnc(int a ){}

 void * ptr = cast(void*)cast( void function( int )) & fnc;

Yes, that does seem to choose the (int) overload. Although what's really odd is that getting the address of fnc without any cast before it gets the address of the overload that was defined first. Personally I think it should be an error, as it's ambiguous..
Feb 24 2007
next sibling parent reply Chris Nicholson-Sauls <ibisbasenji gmail.com> writes:
Jarrett Billingsley wrote:
 "Frank Benoit (keinfarbton)" <benoit tionex.removethispart.de> wrote in 
 message news:erpk4o$1oom$1 digitalmars.com...
 I want to assign a function ptr to a void* variable.

 There are no compile error in case the function is a overloaded one. Is
 this a bug?

 How to select the correct function? I tried a cast, and it seams to work.

 void fnc(){}
 void fnc(int a ){}

 void * ptr = cast(void*)cast( void function( int )) & fnc;

Yes, that does seem to choose the (int) overload. Although what's really odd is that getting the address of fnc without any cast before it gets the address of the overload that was defined first. Personally I think it should be an error, as it's ambiguous..

And now one of the classic proposals, once again. :) void* ptr = cast(void*) &fnc(int) ; So nice, so concise. -- Chris Nicholson-Sauls
Feb 24 2007
parent reply "Frank Benoit (keinfarbton)" <benoit tionex.removethispart.de> writes:
 And now one of the classic proposals, once again.  :)
 
 void* ptr = cast(void*) &fnc(int) ;

Is this perhaps a problem with context free syntax? It is not clear, if this is a "get function pointer address" or a "call function" operation. void* ptr = cast(void*) &fnc( Something ) ; To decide this, the compiler needs to have the arguments completely resolved. Then he can see if they are types, or not.
Feb 26 2007
parent BCS <ao pathlink.com> writes:
Reply to Frank,

 And now one of the classic proposals, once again.  :)
 
 void* ptr = cast(void*) &fnc(int) ;
 

It is not clear, if this is a "get function pointer address" or a "call function" operation. void* ptr = cast(void*) &fnc( Something ) ; To decide this, the compiler needs to have the arguments completely resolved. Then he can see if they are types, or not.

The "address of" should resolve that because you can't take the address of a return. OTOH that would introduce L-value/R-value into the grammar. Maybe the syntax of a function call could allow a type list or an expression list (but not a mixed list) and then the semantics would sort it out later. Bahh, The more I think about this stuff the more I respect Walter.
Feb 26 2007
prev sibling next sibling parent "Frank Benoit (keinfarbton)" <benoit tionex.removethispart.de> writes:
 Personally I think it 
 should be an error, as it's ambiguous.. 
 

http://d.puremagic.com/issues/show_bug.cgi?id=1006
Feb 24 2007
prev sibling parent Kirk McDonald <kirklin.mcdonald gmail.com> writes:
Jarrett Billingsley wrote:
 "Frank Benoit (keinfarbton)" <benoit tionex.removethispart.de> wrote in 
 message news:erpk4o$1oom$1 digitalmars.com...
 
I want to assign a function ptr to a void* variable.

There are no compile error in case the function is a overloaded one. Is
this a bug?

How to select the correct function? I tried a cast, and it seams to work.

void fnc(){}
void fnc(int a ){}

void * ptr = cast(void*)cast( void function( int )) & fnc;

Yes, that does seem to choose the (int) overload. Although what's really odd is that getting the address of fnc without any cast before it gets the address of the overload that was defined first. Personally I think it should be an error, as it's ambiguous..

What we really need is a way to get a tuple of all of the function types associated with a given symbol. Something like: fnc.tupleof => Tuple!(void function(), void function(int)) Making the above an error without providing a mechanism like this would adversely affect Pyd, for example. -- Kirk McDonald http://kirkmcdonald.blogspot.com Pyd: Connecting D and Python http://pyd.dsource.org
Feb 24 2007