Syslinux - May 2019 - Debug C32 Module

Hello,

we have wrote a own C32 module, loaded with "DEFAULT mod.c32"

But sometime the module mod.32 are not loaded & started.
How we can debug this ?
Or give some debug output.
In the main of the module there is a printf, but the text are not shown at
booting.

Thanks
  Johann

> we have wrote a own C32 module, loaded with "DEFAULT mod.c32"
> 
> But sometime the module mod.32 are not loaded & started.
> How we can debug this ?
> Or give some debug output.
> In the main of the module there is a printf, but the text are not shown
> at booting.
 
 
If you are building the binaries by yourself, then nobody really knows 
where the problem could be, considering that even the current git 
master head fails for UEFI mode.

If you are using some package from some distro, or perhaps upstream 
6.04-pre1, please include such details in the future.

Yours would not be the first report about display problems when using 
syslinux.efi. One such report (among others) is about lua.c32, also 
failing to correctly display output text; the "output" is there, but
it
cannot be seen/read.

Having said that, at least one test could be performed anyway, just in 
case.

Instead of using:

###
DEFAULT mod.c32
###


please try:

###
DEFAULT modlabel
PROMPT 1

LABEL modlabel
COM32 mod.c32
###

The point is to use a label for the DEFAULT directive, instead of a 
non-label command.

With this minimal cfg file, When you boot you should at least get to 
the Syslinux "boot" prompt. At that point, press [ENTER] in order to 
execute the default label.

Probably the result won't change from your previous test, but at least 
you will be able to discard the potential problem in the DEFAULT 
directive.

Other than that, _perhaps_ the following might help someone with the 
relevant skills (although, please note that the whole page is rather 
outdated and possibly not very much relevant for UEFI, but YMMV):

 
syslinux.org/wiki/index.php/Development/Debugging#Syslinux_Dynamic_Debug
ger 

Regards,
Ady.

Hello,
> -----Urspr?ngliche Nachricht-----
> Von: Syslinux <syslinux-bounces at syslinux.org> Im Auftrag von Ady
Ady via
> Syslinux
> Gesendet: Freitag, 24. Mai 2019 16:56
> An: syslinux at syslinux.org
> Betreff: Re: [syslinux] Debug C32 Module
> 
> > we have wrote a own C32 module, loaded with "DEFAULT
mod.c32"
> >
> > But sometime the module mod.32 are not loaded & started.
> > How we can debug this ?
> > Or give some debug output.
> > In the main of the module there is a printf, but the text are not
> > shown at booting.
> 
> 
> If you are building the binaries by yourself, then nobody really knows
where
> the problem could be, considering that even the current git master head
fails
> for UEFI mode.
> 
> If you are using some package from some distro, or perhaps upstream 6.04-
> pre1, please include such details in the future.
> 
> Yours would not be the first report about display problems when using
> syslinux.efi. One such report (among others) is about lua.c32, also failing
to
> correctly display output text; the "output" is there, but it
cannot be
> seen/read.
> 
> Having said that, at least one test could be performed anyway, just in
case.
> 
> Instead of using:
> 
> ###
> DEFAULT mod.c32
> ###
> 
> 
> please try:
> 
> ###
> DEFAULT modlabel
> PROMPT 1
> 
> LABEL modlabel
> COM32 mod.c32
> ###
I will look to change this.
> 
> The point is to use a label for the DEFAULT directive, instead of a
non-label
> command.
> 
> With this minimal cfg file, When you boot you should at least get to the
> Syslinux "boot" prompt. At that point, press [ENTER] in order to
execute the
> default label.
> 
> Probably the result won't change from your previous test, but at least
you
> will be able to discard the potential problem in the DEFAULT directive.
> 
> Other than that, _perhaps_ the following might help someone with the
> relevant skills (although, please note that the whole page is rather
outdated
> and possibly not very much relevant for UEFI, but YMMV):
> 
> 
> syslinux.org/wiki/index.php/Development/Debugging#Syslinux_Dynamic_D
> ebug
> ger
Thanks.
> 
> Regards,
> Ady.
> 
> 
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> https://lists.syslinux.org/syslinux
I have found my problem.
It was an old entry "DISPLAY  some_filename"
Without exist file with this name. Than the module crash (sometime, not always)
Now I have remove the DISPLAY entry and looks good.

Thanks
  Johann