[Freeciv-Dev] Re: (PR#7390) python code generators and BUILT_SOURCES

["Jason Dorje Short" <jdorje@xxxxxxxxxxxxxxxxxxx>]

<URL: http://rt.freeciv.org/Ticket/Display.html?id=7390 >

Raimar Falke wrote:
> <URL: http://rt.freeciv.org/Ticket/Display.html?id=7390 >
> 
> On Fri, Feb 06, 2004 at 06:20:49PM -0800, Jason Dorje Short wrote:
> 
>><URL: http://rt.freeciv.org/Ticket/Display.html?id=7390 >
>>
>>Jason Dorje Short wrote:
>>
>>><URL: http://rt.freeciv.org/Ticket/Display.html?id=7390 >
>>>
>>>I ran across
>>>
>>>http://www.gnu.org/software/automake/manual/html_node/Sources.html#Sources
>>>
>>>where it explains dependency calculations and how they affect two-stage 
>>>builds.
>>>
>>>It seems to me that a normal build (after a clean cvs checkout) succeeds 
>>>only by chance; because the generator happens to be run first.  To 
>>>formalize this perhaps a BUILT_SOURCES directive should be added.
>>
>>Hmm.
>>
>>Obviously a build of a clean cvs checkout will work, since the built 
>>sources are included in it already.
>>
>>What might fail is if you change packets.def and then recompile.  If it 
>>so happens that (for instance) packets.o is compiled before 
>>packets_gen.h, then the compilation may not be correct.  A second run of 
>>"make" would be required to fix it.
> 
> 
> The extra dependency:
> 
>   packets_gen.h packets_gen.c: packets.def generate_packets.py
>           ./generate_packets.py
> 
> should take care of this. Or do I miss something here?

You do, but so do I.

The dependency that isn't already known is

   packets.c : packets_gen.h

since these .c : .h dependencies are generated as a side effect of 
compilation (in .deps).  So I think if you get a clean checkout, change 
packets.def, and then try to compile you _could_ come up with a wrong 
compilation because packets.o is compiled before packets_gen.h.  Most 
likely the linking step will fail.  This will be fixed by running "make" 
a second time.

But the first time you compile, this dependency will be generated, and 
you won't have any more problems.

So this is a very minor issue.

Now if packets_gen.[ch] were taken out of CVS it would become a bigger 
issue.  And it would be easy to fix:

   BUILT_SOURCES = packets_gen.c packets_gen.h

jason