[Libreoffice] clean rebuilds needed

[Michael Stahl]

On 26.09.2011 22:27, Stephan Bergmann wrote:
> On 09/26/2011 10:01 PM, Bjoern Michaelsen wrote:

>> No need for such theory, as for all practical proposes, there is ccache
>> doing exactly that (although with a bit of addition IO). As for finer
>> granularity: With the practical reality of C/C++ with preprocessing,
>> context sensitive syntax and commandline switches to influence the
>> compile result there is little hope for such a thing existing _and_ be
>> reasonably fast (read: orders of magnitude faster than just frigging
>> compiling it).
> 
> "there is ccache doing exactly that": but not everything is being built 
> by the C/C++ compilers...
> 
> "finer granularity": I did not mean finer granularity within C/C++ files 
> (so that a changed header does not necessarily cause rebuild of every 
> file including it), but rather within the makefiles themselves (so that 
> a change to one recipe in one makefile would not cause everything to be 
> rebuilt if we had targets depend on the makefiles their recipes come from):

i remember reading that kbuild (the linux build system) writes the
commands that were used to build a target into its dependency file or
something like that; if the command changes, then the target is rebuilt.

the GNU make book by Mecklenburg contains a description of how it works.