[fpc-pascal] Re: using macros

[dhkblaszyk]

  

On 1 okt '12, dhkblas...@zeelandnet.nl wrote: 

> I need to
translate this: #define mymalloc(x,y) (x*)malloc((y)* sizeof(x)) 
> 
>
Is it possible using macro's in FPC or do I need to convert it to a
procedure? How would I cast the pointer in the latter case (without
having to change the sourcecode significantly)? 
> 
> Regards,
Darius

Thanks all, I decided to use an inline function and not to cast
the return pointer. However, I've got another interesting one. Does
someone have an idea how I could implement this? 

#define MYPRINT(var1)
printf(# var1 ":%dn", var1) 

Calling the macro as such :
MYPRINT(sizeof(int)); 

will yield: sizeof(int):4, which is useful for
debugging. 

Will I need RTTI for this? I never used it before so I
might be wrong. 

Darius

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Re: [fpc-pascal] using macros

[Marco van de Voort]

In our previous episode, dhkblas...@zeelandnet.nl said:

A bit late, but:

> I need to translate this: #define mymalloc(x,y) (x*)malloc((y)*
> sizeof(x)) 

Impossible.

1. FPC macros can't be parameterized
2. less problematic, but macros don't import over unit borders,
   you'd have to put the macro in an inc file and include it everyhwere.

The usual trick, converting to procedure is hard because

3. There is no way to pass something typeless to a function and then get
   the size of it. This make emulating it with functions hard.
4. the generic part (returning a typed pointer) will be impossible,
requiring a cast.

> Is it possible using macro's in FPC or do I need to convert
> it to a procedure?

Neither is possible I think for the general case. The most sane way is to
make it a three parameter function and pass sizeof(x);

That will require two fixes though, every 

z:=malloc(x,y) 

will have to be changed to

  z:=px(malloc(x,y,sizeof(x)));

> How would I cast the pointer in the latter case (without having to change
> the sourcecode significantly)?

You can't. Macros are illdefined, and thus hard to port or convert. GIGO
principle.
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[fpc-pascal] Re: using macros

[leledumbo]

Those macros are simply to reduce typing, better use true debugger. Even if
RTTI can (which I believe not), it would be an abuse of the feature.

Macros in FPC aren't as flexible as in C for a purpose IMHO: it's often
abused as the way you show.



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Re: [fpc-pascal] using macros

[Marco van de Voort]

In our previous episode, Marco van de Voort said:
> 3. There is no way to pass something typeless to a function and then get
>the size of it. This make emulating it with functions hard.

Btw, Modula2 allows to pass any type of defined size to an ARRAY OF BYTE
open array (and thus such functions also get the size). Its one of those
things I missed going back to Pascal.
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[fpc-pascal] Using database-specific functionality with TSQLConnector

[Reinier Olislagers]

Hi list,

For a fpcunit database test listener I'm implementing multi-connector
support using TSQLConnector. This seems to work nicely.

If the Firebird connector is chosen and the hostname is empty, I assume
Firebird embedded is used and if not present, a database needs to be
created using .CreateDB

For this, I need TIBConnection-specific CreateDB. Currently I've managed
to do that with the Proxy property of the TSQLConnector, which however
is protected.
Also it appears CheckProxy is needed:

{ THackSQLConnector }
THackSQLConnector = class(TSQLConnector)
  //we really only want access to a working proxy
private
  function GetProxyConnector: TSQLConnection;
public
  Property ProxyConnection : TSQLConnection Read GetProxyConnector;
end;

function THackSQLConnector.GetProxyConnector: TSQLConnection;
begin
  CheckProxy; //seems to be required to get valid proxy
  result:=inherited Proxy;
end;

and

var
FConn: THackSQLConnector;
...

  IBConn:TIBConnection;
...
IBConn:=TIBConnection(FConn.ProxyConnection);
IBConn.UserName:=FConn.UserName;
IBConn.Password:=FConn.Password;
IBConn.DatabaseName:=FConn.DatabaseName;
...
IBConn.CreateDB;

Is that the best/easiest way? Would it make sense to make the proxy code
in TSQLConnector public?
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