[Caml-list] byte-code and -fno-defer-pop

[Caml-list] byte-code and -fno-defer-pop

[Markus Mottl]

Hello,

C-files in the OCaml-distribution are usually compiled with -fno-defer-pop
when they are supposed to be used with byte code, too. What is the
rationale behind? Is this only intended to limit stack growth a bit or
are there other reasons? This opposite of this option is normally turned
on when optimisation (-O) is used. Would you recommend this setting
generally for C-code that should cooperate with OCaml-byte code?

Thanks for enlightenment!

Regards,
Markus Mottl

-- 
Markus Mottl                                             markus@oefai.at
Austrian Research Institute
for Artificial Intelligence                  http://www.oefai.at/~markus
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Re: [Caml-list] byte-code and -fno-defer-pop

[Xavier Leroy]

> C-files in the OCaml-distribution are usually compiled with -fno-defer-pop
> when they are supposed to be used with byte code, too. What is the
> rationale behind?

There used to be a bug in gcc whereas code using computed gotos (such
as the OCaml bytecode interpreter) would be incorrectly compiled
unless the -fno-defer-pop option is given.  I don't know if this has
been fixed in recent versions of gcc.

At any rate, you're correct that -fno-defer-pop is needed only for
compiling byterun/interp.c, and applying it to all bytecode-related C
files is a bit excessive.

> Is this only intended to limit stack growth a bit or
> are there other reasons? This opposite of this option is normally turned
> on when optimisation (-O) is used. Would you recommend this setting
> generally for C-code that should cooperate with OCaml-byte code?

No, it shouldn't be necessary.

- Xavier Leroy
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