[Lazarus] some workarounds [Re: Debugger problems]

[Martin Friebe]

Graeme Geldenhuys wrote:
> On Sat, Feb 21, 2009 at 12:49 AM, Hans-Peter Diettrich
> <DrDiettrich1 at aol.com> wrote:
>   
>> In most cases I cannot inspect local variables, due to "no such symbol
>> in context" errors, even with fully disabled optimizations.
>>     
>
> This is exactly the errors I get. I develop under Linux only, so it
> doesn't seem to be a platform issue. I gave up trying the integrated
> debugger and simply use Log(..) or Writeln(...) calls now
>   
It is true that there are cases where GDB does not find Symbols, until 
this can be fixed in a better way, here are a few cases and workarounds

1) properties

This is apparently the most common case? GDB has no concept of 
properties. Also properties can refer to functions.
Possible workarounds:
a) if a property refers to a Variable, use CodeTools to find the 
variable name, and expect the Variable. Usually property abc, will point 
to variable Fabc
b) if the property refers to a method, there is no workaround, since 
currently you can not force GDB to execute any method. Executing the 
Method could also change the state of the debugged application.

2) Nested Procedures

GDB does only see the current stack frame.

Procedure SomeObject.ABC
var x: integer;
  Procedure Nested
  begin
  end
begin
end

While in "Nested" gdb can NOT see anything that belongs to ABC. (this is 
it can not see "x", and it can not see "self" (the object), or any 
variable on the object)

Possible Workaround:
Open the Stack Window, and change the current frame. I know this is a 
bit dull, because you have to change it after each execution step.

2a)
The same applies to hints in the source window. *Variables*  will only 
show if the stackframe is correct

3)
Sometimes Variables are pointers in GDB, where they are not in Pascal.

if you type SomeObject as a watch it may just say "TSomeClass 0x23ab76" 
=> try typing SomeObject^

4) Dynamic arrays
See the following post for a workaround (again it is too complex for 
every day use, but it may help for desperate occasions)
http://forum.lazarus.freepascal.org/index.php/topic,4763.msg22954.html#msg22954