[syslinux] debugging pxelinux

Patrick Welche prlw1 at cam.ac.uk
Tue Apr 14 16:13:57 PDT 2015


On Tue, Apr 14, 2015 at 03:20:08PM -0400, Gene Cumm wrote:
> > I thought I would try to find out how pxelinux copes with this, by trying
> > to insert printfs in pxe_init, but nothing gets printed.
> 
> This is normal.

Can you give me hint as to why setting

> >         DEBUGOPT = -DDEBUG=1 -DDEBUG_STDIO -DCORE_DEBUG=1

changes that state of normality? (AFAICT dprintf.h defines dprintf to
printf, so why wouldn't using printf directly work? printf.o gets built
regardless of DEBUG settings AFAICT.)

> > From looking at com32/include/dprintf.h, it looks as though all this does is
> > to define dprintf to printf, so why is it that if don't define DEBUG_STDIO
> > and CORE_DEBUG, and just use printf directly, nothing appears?
> 
> If ldlinux.c32 isn't loaded, printf() shouldn't work though printf()
> in 1 context might not be the same as another.

So my assumption below is wrong? How does DEBUG_STDIO/CORE_DEBUG affect
the loading of ldlinux.c32?

> > I assume (given the dprintfs) that ldlinux.c32 is loaded by the time
> > pxe_init is run, so printf calls should be legal.


Thanks!

Patrick


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