Re: Help with differing build environments

[Geoffrey Huang]

Hi Chris,

Thanks for the response.  Yeah - I'd read about this in the manuals.  I 
don't really like the prospect of having #if statements throughout the 
code, especially since the use of the functions in question is quite 
widespread.

Additionally, it isn't just a matter of using my version of the function 
vs. the system's function.  I don't want my toolkit's functions linked 
in when unnecessary, and likewise, I don't want the system's functions 
linked in when unnecessary.

I think I've worked it out to have configure check for the presence of 
the API/header files in question, then based on that, conditionally set 
the appropriate search-path for the header file.  Likewise, based on 
this condition, I'll have configure compile and link the appropriate 
code, so:

if BUILT_IN_DATASTRUCTS
    DATASTRUCTS=
    DATASTRUCT_INCLUDEDIR=system/include
else
    DATASTRUCTS=datastruct_dir
    DATASTRUCT_INCLUDEDIR=toolkit/datastruct_dir/include
endif

INCLUDES=-I$(top_srcdir) -I$(DATASTRUCT_INCLUDEDIR)
SUBDIRS=$(DATASTRUCTS)

Thanks again for the suggestion.

-g

Chris Albertson wrote:
> This is covered in the manuals in more detail but in general the idea is 
> that you get "configure" to test for some required API and if found
> set a variable like "HAVE_FOOBAR" if libFOOBAR is found and usaable
>
> Then inside your code you use a bunch of #if statemnets to either use 
> the system API or yours.
>
> #if HAVE_FOOBAR
> #include <foo_bar.h>
> #else
> #include <My_foo_bar_replacement.h>
> #endif
>
> #if HAVE_FOOBAR
>   var = SillyFunction(x);
> #else
>   var = MyRewiteOfSillyFunction(x);
> #endif
>
> Sometimes you can simply fall back to another function if one is
> not available  Like using "fsync" if "fdatasync" is not available.
> (older Solaris lacks fdatasync) but I would never write #if SOLARIS.
> I'd use HAVE_FDATASYNC.
>
>
> Geoffrey Huang wrote:
>
> > Hi there,
> >
> > I have a question on how to use autotools in differing build 
> > environments.
> >
> > I'm working on a project that's meant to be a portable library.  On 
> > some systems, I'll be using a set of APIs provided by the platform.  
> > In these cases, I want autotools to look for the system's header files 
> > for the API's.  Likewise, I want autotools to look for the 
> > system-provided .c-files for these API's.
> >
> > On other targets, the system doesn't provide the API's, so I want 
> > autotools to use the code I've implemented in the portable library 
> > itself.
> >
> > How would I go about doing this?  I've considered using the 
> > AC_CANONICAL_SYSTEM statement in configure.in to get me the target 
> > system.  However, that directive only seems to recognize standard gnu 
> > platforms.  Some of my platforms aren't standard.
> >
> > Then I considered using the AM_CONDITIONAL test to specify the system 
> > type directly to the configure script, but I have doubts that this is 
> > the best way.
> >
> > Anyhoo, I'd appreciate any help.
> >
> > -g
> >
> >
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