[fpc-devel] Binary size discrepancy with -a

[Sven Barth]

J. Gareth Moreton <gareth at moreton-family.com> schrieb am So., 19. Juli
2020, 05:09:

> Hi everyone,
>
> I've noticed something a bit weird with the Free Pascal Compiler when
> you use the the -a option to dump the compiled assembly files... the
> resultant binaries are sometimes smaller.  I recently tried it with
> Lazarus under x86_64-win64 (using "make distclean all install" with
> FPCOPT):
>
> (-O4 -OoCONSTPROP)
> 241,010,289 bytes - lazarus.exe
>
> (-a -O4 -OoCONSTPROP)
> 235,655,062 bytes - lazarus.exe
>
> Anyone else noticed this? Logically, shoudn't the EXE files be
> completely identical?
>

On x86 the difference is that this switches to the external assembler
instead of using the internal one. That can result in differently generated
files. You could compare the generated *.o files or use -Xm to compare the
linker maps.

Regards,
Sven

>
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