[fpc-devel] Re: weird interaction with gdb / stepping / 2.7.1

[Martin]

I got the attached sample from one of the 2people. With the instructions 
below:

> Attached a small program that shows ME the problem
> Included is the generated laz.log.
> My breakpoint is on line 39 in unit1.pas
> As soon as I hit the AnsiSTRING variable named xstring the debugging
> jumps to FOnClick(Self) in control.inc

I have no 64 bit linux to test myself. I therefore do not know, if it 
will indeed reproduce.
According to the reporter, it happens with stabs and dwarf.

I am not sure which versions of gdb (the reporter had 7.5.1) Testing 
with an upgraded 7.5.9 or 7.6 is of limited use, since both crash easily 
if debugging fpc generated apps.

---------------
If the report is correct, then apps generated with fpc 2.7.1 may not be 
debug-able in gdb (unless you want to step through ansistring internals)

Maybe someone can give it a try?

And if it is reproducible, find if it is fpc or gdb?


On 14/05/2013 11:03, Martin wrote:
> I have 2 matching reports (but so far unable to reproduce myself)
>
> - both are 64 bit
> - at least one is linux and uses gdb 7.5.1
>   I believe the other is linux too, not sure what gdb, (and he tested 
> on win (not sure 64 or 32bit) where it did not happen)
>   [ this may point to a linker issue (maybe) ]
>
> - They both state, that they did not use optimization, or smart linking
>
> When stepping (step over) GDB suddenly stops in fpc_ansistring_copy 
> (or other functions in the RTL that are called during the step)
>
>
> I am seeking for any ideas....
>
> I know it likely is to be something in GDB and needs to be asked 
> there. But it appears to react to some diff bthat happened in fpc 
> (2.6.x) seems not to trigger it).
>
> And other than the fact that those functions are optimized, and do not 
> have a full gdb detectable stackframe, there is nothing I could 
> suspect....
>
>
> possible: http://bugs.freepascal.org/view.php?id=14399

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