Re: master has switched from Automake to GNU Make

[Paul Eggert <eggert@cs.ucla.edu>]

On 03/21/2017 10:42 AM, Tom Tromey wrote:
> IIUC it will cause a full
> rebuild for any re-run of configure, no matter now innocuous.

Yes, it does require recompiling to rebuild *.o files and executables. 
Though that isn't a full build, it can take quite some time. On my aging 
desktop, 'configure' takes 58 seconds, and the followup 'make' takes 61 
seconds.

There is a tradeoff between speed and correctness, since 'configure' can 
change Makefiles, which means a full rebuild might be needed no matter 
what. But you're right, the change I installed was probably too 
aggressive for typical use. So I changed 'configure' back, so that it no 
longer removes *.o and dependency files. This means Robert Marshall will 
probably have to do a full rebuild by hand.

> FWIW Automake implements a solution to the "deleted header file"
> problem, just to deal with situations like this.

That solution wouldn't have worked for this particular problem even if 
we were still using Automake, as the dependencies in question were not 
generated by GCC or by Automake. Sometimes after a big change, one must 
simply do the full './autogen.sh; ./configure; make' dance, as our 
default shortcuts are not safe in general.