[fpc-devel] Breaking change in FPC 2.6.1

[Sven Barth]

On 01.05.2012 13:57, Martin Schreiber wrote:
> On Tuesday 01 May 2012 13:50:49 Sven Barth wrote:
>> On 01.05.2012 13:50, Martin Schreiber wrote:
>>>> Anyway, the change is undone, we're back on TBookmarkStr.
>>>> TBookMarkStr is now marked deprecated. Revision 21155.
>>>
>>> Thank you very much. That means it is not possible to work with fixes_2_6
>>> without "deprecated" warnings? TDataset.Bookmark is of type TBookmarkStr
>>> but TBookmarkStr is deprecated?
>>
>> Exactly. These were added to remind everyone who uses TBookmarkStr that
>> there WILL be a change after 2.6.2 has been released (thus in 2.6.3) as
>> Michael explained.
>>
> What do you suggest to avoid the warning?

You can locally disable warnings by using the $warn directive (not 
documented yet it seems, but available in 2.6.0).

It looks like this:

{$warn MSGID (on|off|error)}

* on: MSGID will be emitted as a warning
* off: MSGID will not be emitted
* error: MSGID will be emitted as an error (and handled as such by the 
compiler!)

You can find out the MSGID by passing "-vq" to the compiler then it will 
additionally print the ID for each message it writes. For the case of 
"deprecated" there are two message IDs: One which is used if a custom 
message is given and one for the other case. For the first the ID is 
5066 and for the latter 5043.

The following is a demonstration of the potential usage of $warn:

=== example begin ===

program warntest;

{$mode objfpc}

type
   TTest = class
     procedure Test; deprecated 'Test';
   end;

procedure TTest.Test;
begin

end;

var
   t: TTest;
begin
{$push} // <= used to restore the state afterwards; you could use {$warn 
5066 on} as well
{$warn 5066 off}
   t.Test; // here no warning will be emitted
{$pop}
   t.Test; // here a warning will be emitted
end.

=== example end ===

Alternatively you can also use

{$warn symbol_deprecated off}

which will switch of both custom and non-custom deprecated messages for 
symbols (units have an extra name).

Here is a list of all those recognized identifiers (out of Delphi 
compatibility):

CONSTRUCTING_ABSTRACT
IMPLICIT_VARIANTS
NO_RETVAL
SYMBOL_DEPRECATED
SYMBOL_EXPERIMENTAL
SYMBOL_LIBRARY
SYMBOL_PLATFORM
SYMBOL_UNIMPLEMENTED
UNIT_DEPRECATED
UNIT_EXPERIMENTAL
UNIT_LIBRARY
UNIT_PLATFORM
UNIT_UNIMPLEMENTED
ZERO_NIL_COMPAT
IMPLICIT_STRING_CAST
IMPLICIT_VARIANTS
NO_RETVAL
SYMBOL_DEPRECATED
SYMBOL_EXPERIMENTAL
SYMBOL_LIBRARY
SYMBOL_PLATFORM
SYMBOL_UNIMPLEMENTED
UNIT_DEPRECATED
UNIT_EXPERIMENTAL
UNIT_LIBRARY
UNIT_PLATFORM
UNIT_UNIMPLEMENTED
ZERO_NIL_COMPAT
IMPLICIT_STRING_CAST
IMPLICIT_STRING_CAST_LOSS
EXPLICIT_STRING_CAST
EXPLICIT_STRING_CAST_LOSS
CVT_NARROWING_STRING_LOST

Regards,
Sven