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List:       linux-ha-dev
Subject:    Re: [Linux-ha-dev] libltdl changes question
From:       Alan Robertson <alanr () unix ! sh>
Date:       2001-05-22 19:46:18
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Michael Moerz wrote:
> 
> On Sun, May 20, 2001 at 10:36:38PM -0600, Alan Robertson wrote:
> > Michael Moerz wrote:
> > >
> [snip]
> >
> > These aren't real wonderful.   They're way too long and not very
> > self-explanatory...  They also hide the C syntax in a way that isn't helpful
> > - it's just obfuscantion.
> >
> O.k. I will not do it like that.
> 
> > Why would you make it named hb_comm_module.h and not just hb_module.h?  I
> > don't think these two files have to be different.
> >
> If we do it like you are suggesting, we definitly do not need further
> module headers.
> 
> > As time goes on we're going to move everything to one uniform, simpler and
> > more powerful module loading interface...
> >
> > I'd like to change the linux-ha software so that everything is a module -
> > even the configuration parser.  I won't do it by adding more module
> > interfaces, but instead by collapsing down to one.
> >
> Well that one might become tricky.
> 
> [snip]
> >
> > I would do two things:
> >
> > Every function in a file has the same module name.  I would make a single
> > #define MODULE, or HB_MODULE or something that the other macros used like a
> > global variable.  This works just fine because you can never put more than
> > one module in a file...  Then it might read more like this:
> >
> > #define MODULE_NAME "crc"  /* Too bad we can't use __FILE__ here... */
> > #include <ha_modules.h>
> >
> > /* From ha_modules.h... */
> > #ifndef _HA_MODULES_H
> > #define _HA_MODULES_H
> >
> > /*
> >  *    SPECIAL NOTE:
> >  *    Must define MODULE_NAME *before* including this header if you
> >  *    want to use the EXPORT function.
> >  */
> > ifdef __STDC__
> > #     define CONC(x, y)      x##y
> > #     ifdef MODULE_NAME
> > #             define EXPORT(name)   MODULE_NAME##_LTX_##name
> > #     endif
> > #else
> > #     define CONC(x, y)      x/**/y
> > #     ifdef MODULE_NAME
> > #             define EXPORT(name)   MODULE_NAME/**/_LTX_/**/name
> > #     endif
> > #endif
> > #endif /* _HA_MODULES_H */
> > /* End of ha_modules.h */
> >
> > int
> > EXPORT(hb_dev_init) (void) {
> >       ...
> > }
> >
> That would define MODULE_NAME_LTX_hb_dev_init and not crc_LTX_hb_dev_init
> since the macro MODULE_NAME is not expanded. That's somewhat strange,
> isn't it?
> something like
> #define EXPORT(module, function) module##_LTX_##function
> works properly.
> As it seems we will have to live with that EXPORT(module, function)
> macro, but perhaps someone else has got an idea how to make the
> expansion work?

This is really weird...

#define MODULE foo
 
#define EXPORT2(module, function) module##__LTX__##function
#define EXPORT(function) EXPORT2( MODULE, function)
#define TEST(function) printf("%s %s", MODULE, function)
 
EXPORT(main)
EXPORT2(MODULE, main)
TEST(bar)

The preprocessor output from this is:
 
  MODULE__LTX__main
 MODULE__LTX__main
printf("%s %s", foo ,  bar )



I'll ask my local LUG...

Other opinions are much appreciated.

	-- Alan Robertson
	   alanr@unix.sh
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