Re: CHECK_STRUCTS/dmpstruct.h mechanism is broken.

[Andy Moreton <andrewjmoreton@gmail.com>]

On Thu 11 Apr 2019, Paul Eggert wrote:

> On 4/11/19 12:15 PM, Eli Zaretskii wrote:
>> You want to test for system-dependent features with Make?  How does
>> one do that?
>
> You execute the test as a 'make' rule that records the test's result as
> a makefile snippet (or as a .h file, or whatever).

Which gives you a buggy reimplementation of half of autoconf.

>> IME, the slowest part is byte compilation of Lisp files.  Of course,
>> that is only a significant factor when you bootstrap or rebuild large
>> parts of Emacs, but still.
> Yes. Typically I don't recompile Lisp files so the bottleneck for me is
> 'configure'.
>
> Moreover, Lisp file recompilation is parallelized so it's reasonably
> fast on larger platforms (the wave of the future :-), whereas
> 'configure' will remain slow. I just now timed it, and './configure'
> took 29 real-time seconds whereas 'cd lisp; make -j16 compile-always'
> took 38 real-time seconds; this was with two circa-2013 Xeon E5-2640 v2
> CPUs with 8 cores each. So on a 32-core platform, I expect ./configure
> to take longer than byte-compiling all the Lisp files - i.e.,
> 'configure' is ridiculously slow.

You could help speed up configure by fixing the ridiculously long set of
checks for supported compiler flags that come from gnulib. That is
glacially slow and mostly pointless.

    AndyM