[fpc-devel] Issue 3.2.3 (ok in 3.3.1) Win64 "raise exception" does not go to "except"

[J. Gareth Moreton]

Found the reason for it, or at least what looks like the reason... the 
RemoveDeadCodeAfterJump routine, which removes all instructions between 
a "jmp" instruction and the next live label (since those instructions 
will never get executed), doesn't stop if it hits the SEH section and 
strips all that too.  Because of the "while True do" block covering the 
entire procedure, the function epilogue is suppressed by an 
unconditional jump and so gets stripped out (arguably fine in this 
case), but the optimizer doesn't think to stop if it goes past the final 
instruction.  I'll start doing a bisect to see if I can locate where 
this is corrected... or just write it myself if that fails.

Gareth aka. Kit

On 15/01/2022 15:25, Florian Klämpfl via fpc-devel wrote:
> Am 13.01.2022 um 16:49 schrieb Martin Frb via fpc-devel:
>> In the  below code compiled with 3.2.3 (today and early Dec)
>> when the exception is reached the app exits.
>>
>> There is no code from finally, nor from except block executed.
>>
>> The "randomize" is just to put some code into each block. No special 
>> meaning otherwise.
>>
>> This issue is on Win64. (works for 32 bit Win)
>> And appears to be ok in 3.3.1.
>
> It happens only with -O1 or higher, the compiler optimizes away all 
> the exception data (diff between -O- and -O1):
>
> 176,180d170
> < # [37] end;
> <       nop
> <       leaq    (%rbp),%rsp
> <       popq    %rbp
> <       ret
> 183,195d172
> <       .long   3
> <       .long   0
> <       .rva    .Lj27
> <       .rva    .Lj28
> <       .rva    P$PROJECT1$_$FOO_$$_fin$00000002
> <       .long   0
> <       .rva    .Lj22
> <       .rva    .Lj23
> <       .rva    P$PROJECT1$_$FOO_$$_fin$00000003
> <       .long   1
> <       .rva    .Lj20
> <       .rva    .Lj17
> <       .rva    .Lj18
> 199a177
> > # [37] end;
>
> Maybe Gareth can have a look?
>
>>
>>      program Project1;
>>      {$mode objfpc}{$H+}
>>
>>      uses SysUtils;
>>
>>      var
>>        bar: boolean;
>>
>>      procedure Foo;
>>      begin
>>        while true do begin
>>          try
>>            try
>>              try
>>                if bar then
>>                  raise Exception.Create('');
>>                Randomize;
>>              finally
>>                Randomize;
>>                try
>>                  Randomize;
>>                finally
>>                  Randomize;
>>                end;
>>              end;
>>              Randomize;
>>            finally
>>              Randomize;
>>            end;
>>            Randomize;
>>          except
>>            bar := false;
>>            Randomize;
>>          end;
>>        end;
>>      end;
>>
>>      begin
>>        bar := true;
>>        Foo;
>>      end.
>>
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>
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