bug#23476: 25.0.93; Visiting C files on master signals an error

[Óscar Fuentes]

Eli Zaretskii <eliz@gnu.org> writes:

>> > Btw, I noticed that CC Mode is quite a bit slower on master than it is
>> > on emacs-25 (try searching for "IF_LINT" in xdisp.c), is that related
>> > to these changes in any way?
>> 
>> FWIW, I'm using master version
>> 
>> GNU Emacs 25.0.92.4 (x86_64-pc-linux-gnu, X toolkit) of 2016-04-23
>> 
>> which includes the noise macros feature. Searching for IF_LINT in
>> xdisp.c is instantaneous. Also, on my work with large-ish C++ source
>> files I didn't observe any slow down.
>
> How (with what configure-time options) was your binary built?  Is it
> an optimized build?
>
> And btw, 25.0.93 is not a master branch version, it's an emacs-25
> branch version.  The slowdown I saw was in 25.1.50.106.

Ooops! It is emacs-25 indeed, but with the original noise-macros patch
that was later committed to master by Alan.

My config command is

../emacs/configure --without-toolkit-scroll-bars --with-x-toolkit=lucid

which is optimized, AFAIK.

I have GNU Emacs 25.1.50.1 (i686-w64-mingw32) of 2016-04-21 on a VM
machine and isearching for IF_LINT on xdisp.c on that build is also
instantaneous. Configured and built with no added options. The same
build on a 7 year old netbook also isearches IF_LINT with no perceptible
delay. Moreover, I have installed the `anzu' package, which shows on the
modeline a (M/N) count where N is the total of matches on the buffer and
M is the current match on the series. This possibly adds quite a bit of
work to the bare isearch.

There is no significant change on the time taken for displaying the
buffer when the file is visited too. Quickly pressing the Page/Down key
saturates the CPU on the netbook, but IIRC that also happened before the
noise-macros change.