rax cleared before fnc call on x86_64

[Johannes Bauer]

Hello group,

I'm using gcc to hack some low-level stuff - until recently I was
developing on x86_32 (i686), but now I switched to x86-64. As the
calling convention is different obviously I had to change large portions
of my code. Something was weird, however:

When calling functions, gcc always emits code to clear %rax before the
call is made. Is this some kind of calling convention I'm not aware of?
Can I specify a certain function attribute to stop gcc from emitting
that clearing beforehand?

Kind regards,
Johannes

--
"Meine Gegenklage gegen dich lautet dann auf bewusste Verlogenheit,
verlï¿œsterung von Gott, Bibel und mir und bewusster Blasphemie."
-- Prophet und Visionï¿œr Hans Joss aka HJP in de.sci.physik
<48d8bf1d$0$7510$5402...@news.sunrise.ch>

[Johannes Bauer]

Hi group,

since no reply came in the g++.help group, maybe someone on gcc.help
knows why this is happening? Fullquote attached & fup2 gnu.gcc.help.

Kind regards,
Johannes