bug#30992: 27.0.50; Crash when graphics card switches

bug#30992: 27.0.50; Crash when graphics card switches

[Peter Dyballa]

Hello!

There were reports about failing graphics cards in one or more series' of MacBooks Pro. Mine, 17" early 2011 with Core i7 (2720QM, "Sandy Bridge") and upgraded to 16 GB of RAM, has AMD Radeon HD 6750M and Intel HD 3000. The main board had to be changed in 2013, I think. Apple later took over the cost. Around last Christmas the graphics defect appeared again, triggered possibly by an OS upgrade from Mac OS X 10.6.8 (Snow Leopard) to OS X 10.11.6, El Capitan. My Mac was repaired by soldering one graphics IC (did not care which). The repair was not perfect, still "glitches" happen, particularly when RAM is overcrowded (disk has some ten GB free space for VM) because at least the built-in intel HD Graphics uses normal RAM. An application, gfxCardStatus 2.3, allows to monitor switching and also to set this or that active. I use this function to clean the screen when artefacts are left from "voluntary" switches (Google Earth or Java Console activate always the Radeon), one Java application seems to produce these artefacts often.

When clearing the screen by setting this and than that and than again this graphics active (or such) the NS variant of GNU Emacs 27.0.50 crashes very often while the X clients, GNU Emacs 26.0.90, simply continue to work. The former was built and installed by MacPorts, the latter is manually compiled.

BTW, I intend to upgrade to OS X 10.13, High Sierra, over Easter.


In GNU Emacs 27.0.50 (build 1, x86_64-apple-darwin15.6.0, NS appkit-1404.47 Version 10.11.6 (Build 15G18013))
 of 2017-12-29 built on Sumac.fritz.box
Repository revision: 0bddbbc5aae621d5875880ac3e63f68d481df7c3
Windowing system distributor 'Apple', version 10.3.1404
Recent messages:
Mark set [7 times]
Mark activated
Mark set [2 times]
Undo!
Mark set
Auto-saving...done
Saving file /Users/pete/böse eMail-Adressen...
Wrote /Users/pete/böse eMail-Adressen
Reverting buffer ‘pete’.
Reverting buffer ‘virtu’. [3 times]

Configured using:
 'configure --prefix=/opt/local --without-ns --without-dbus
 --without-gconf --with-libotf --without-m17n-flt --without-gpm
 --without-gnutls --with-xml2 --with-modules --infodir
 /opt/local/share/info/emacs --with-ns --with-imagemagick
 CC=/usr/bin/clang 'CFLAGS=-pipe -Os -arch x86_64'
 'LDFLAGS=-L/opt/local/lib -Wl,-headerpad_max_install_names -Wl,-no_pie
 -arch x86_64' CPPFLAGS=-I/opt/local/include OBJC=/usr/bin/clang
 'OBJCFLAGS=-pipe -Os -arch x86_64''

Configured features:
JPEG RSVG IMAGEMAGICK NOTIFY ACL LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS
MODULES LCMS2

Important settings:
  value of $LANG: de_DE.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Calendar

Minor modes in effect:
  diff-auto-refine-mode: t
  TeX-PDF-mode: t
  shell-dirtrack-mode: t
  delete-selection-mode: t
  show-paren-mode: t
  midnight-mode: t
  display-time-mode: t
  desktop-save-mode: t
  mac-print-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
/Library/Application Support/Emacs/tex-site hides /opt/local/share/emacs/site-lisp/tex-site
/Library/Application Support/Emacs/punycode hides /opt/local/share/emacs/site-lisp/punycode
/Library/Application Support/Emacs/preview-latex hides /opt/local/share/emacs/site-lisp/preview-latex
/Library/Application Support/Emacs/idna hides /opt/local/share/emacs/site-lisp/idna
/Library/Application Support/Emacs/cmake-mode hides /opt/local/share/emacs/site-lisp/cmake-mode
/Library/Application Support/Emacs/autotest-mode hides /opt/local/share/emacs/site-lisp/autotest-mode
/Library/Application Support/Emacs/autoconf-mode hides /opt/local/share/emacs/site-lisp/autoconf-mode
/Library/Application Support/Emacs/auctex hides /opt/local/share/emacs/site-lisp/auctex
/Library/Application Support/Emacs/site-start hides /Applications/MacPorts/Emacs.app/Contents/Resources/site-lisp/site-start

Features:
(shadow sort mail-extr emacsbug message subr-x puny seq format-spec
rfc822 mml mml-sec password-cache epa epg epg-config gnus-util rmail
rmail-loaddefs mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils cl-extra help-mode latexenc diff-mode
reftex-auc preview prv-emacs tex-buf reftex-dcr reftex reftex-loaddefs
reftex-vars tex-fold noutline outline font-latex byte-opt bytecomp
byte-compile cconv latex tex-ispell tex-style tex crm tex-mode elec-pair
sh-script smie executable dired-aux autorevert filenotify dired-x dired
dired-loaddefs lunar view diary-lib diary-loaddefs solar cal-dst
holidays hol-loaddefs cal-move cal-menu calendar cal-loaddefs shell
pcomplete asy-mode two-mode-mode wid-edit compile comint ansi-color ring
cc-mode cc-fonts easymenu cc-guess cc-menus cc-cmds cc-styles cc-align
cc-engine cc-vars cc-defs derived delsel preview-latex tex-site
auto-loads time-stamp paren midnight time cus-start cus-load desktop
frameset session edmacro kmacro mac-print-mode easy-mmode advice htmlize
cl-seq cl-macs cl gv cl-loaddefs cl-lib time-date tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel term/ns-win ns-win
ucs-normalize mule-util term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode elisp-mode
lisp-mode prog-mode register page menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese composite charscript charprop case-table epa-hook jka-cmpr-hook
help simple abbrev obarray minibuffer cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote kqueue cocoa ns lcms2 multi-tty make-network-process emacs)

Memory information:
((conses 16 633297 30591)
 (symbols 48 34021 6)
 (miscs 40 508 3278)
 (strings 32 84521 4108)
 (string-bytes 1 2366308)
 (vectors 16 53482)
 (vector-slots 8 1624656 182164)
 (floats 8 640 608)
 (intervals 56 32955 0)
 (buffers 992 112))


—
Greetings

  Pete

To most people solutions mean finding the answers. But to chemists solutions
are things that are still all mixed up.

bug#30992: (27.0.50; Crash when graphics card switches)

[Peter Dyballa]

It's actually from the MacPorts port (package) emacs-app-devel @20170918_0+imagemagick+inline+multicolor_font.

—
Greetings

  Pete

"Klingon function calls do not have 'parameters' - they have 'arguments' - and they ALWAYS WIN THEM."

bug#30992: 27.0.50; Crash when graphics card switches

[Alan Third]

On Thu, Mar 29, 2018 at 08:29:00PM +0200, Peter Dyballa wrote:
> When clearing the screen by setting this and than that and than
> again this graphics active (or such) the NS variant of GNU Emacs
> 27.0.50 crashes very often while the X clients, GNU Emacs 26.0.90,
> simply continue to work. The former was built and installed by
> MacPorts, the latter is manually compiled.

Hi, I can’t test this as my lowly macbook pro only has one graphics
card.

Can you get a backtrace from the crash?
-- 
Alan Third

bug#30992: 27.0.50; Crash when graphics card switches

[Peter Dyballa]

> Am 29.3.2018 um 21:21 schrieb Alan Third <alan@idiocy.org>:
> 
> Hi, I can’t test this as my lowly macbook pro only has one graphics
> card.
> 
> Can you get a backtrace from the crash?
> — 

Sorry, I cleaned up my disk in preparation of the coming High Sierra upgrade and certainly deleted the core file. I have files from Apple's Crash Reporter. And since I logged off from my second (professional) account there is no RAM bottleneck and GNU Emacs won't crash when switching between the graphics cards.


BTW, the old --with-mac variant, version 25.3 with patches set 6.8, did never crash although I am using mostly this Emacs. (The NS variant feels somehow inferior.)

—
Greetings

  Pete

The box said "Use Windows 95 or better," so I got a Macintosh.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Peter Dyballa]

On macOS High Sierra, Version 10.13.4, the newly with Xcode 9.3 rebuilt NS variant seems to behave stable. (The previous version was built with the then native tools of OS X El Capitan.)

—
Greetings

  Pete

Don't just do something, sit there.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Alan Third]

On Sat, Apr 07, 2018 at 12:07:36PM +0200, Peter Dyballa wrote:
> On macOS High Sierra, Version 10.13.4, the newly with Xcode 9.3
> rebuilt NS variant seems to behave stable. (The previous version was
> built with the then native tools of OS X El Capitan.)

Thanks for letting us know. I’ll close this bug report, but if the
problem comes back feel free to either reopen it or create a new one.
-- 
Alan Third

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > On macOS High Sierra, Version 10.13.4, the newly with Xcode 9.3
  > rebuilt NS variant seems to behave stable.

How does Xcode relate to building Emacs?

-- 
Dr Richard Stallman
President, Free Software Foundation (https://gnu.org, https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)
Skype: No way! See https://stallman.org/skype.html.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Alan Third]

On Sun, Apr 08, 2018 at 12:33:56AM -0400, Richard Stallman wrote:
> [[[ To any NSA and FBI agents reading my email: please consider    ]]]
> [[[ whether defending the US Constitution against all enemies,     ]]]
> [[[ foreign or domestic, requires you to follow Snowden's example. ]]]
> 
>   > On macOS High Sierra, Version 10.13.4, the newly with Xcode 9.3
>   > rebuilt NS variant seems to behave stable.
> 
> How does Xcode relate to building Emacs?

On macOS it provides the compiler and tools, i.e. clang, make, etc.

It’s possible to install them without Xcode, but most people just use
Xcode.
-- 
Alan Third

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Peter Dyballa]

> Am 8.4.2018 um 06:33 schrieb Richard Stallman <rms@gnu.org>:
> 
> [[[ To any NSA and FBI agents reading my email: please consider    ]]]
> [[[ whether defending the US Constitution against all enemies,     ]]]
> [[[ foreign or domestic, requires you to follow Snowden's example. ]]]
> 
>> On macOS High Sierra, Version 10.13.4, the newly with Xcode 9.3
>> rebuilt NS variant seems to behave stable.
> 
> How does Xcode relate to building Emacs?

The C and C++ compilers come with Xcode. The build process starts with running autogen. Configure then finds:

	configure:5054: /usr/bin/clang --version >&5
	Apple LLVM version 9.1.0 (clang-902.0.39.1)
	Target: x86_64-apple-darwin17.5.0
	Thread model: posix
	InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

And this compiler comes from Apple's Xcode package.

--
Greetings

  Pete

I consider religion godesque.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > > How does Xcode relate to building Emacs?

  > The C and C++ compilers come with Xcode.

Someone told me that there are very tight restrictions on use of Xcode.
Is that true of this version of Xcode?

-- 
Dr Richard Stallman
President, Free Software Foundation (https://gnu.org, https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)
Skype: No way! See https://stallman.org/skype.html.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Peter Dyballa]

> Am 9.4.2018 um 06:28 schrieb Richard Stallman <rms@gnu.org>:
> 
>>> How does Xcode relate to building Emacs?
> 
>> The C and C++ compilers come with Xcode.
> 
> Someone told me that there are very tight restrictions on use of Xcode.
> Is that true of this version of Xcode?

I don't know. Fifteen or such years ago I could register myself as developer for free which allowed me to download and install Xcode. Since then I continue to fetch the newest version. One change was that the Apple Store application is now providing Xcode, so you need another account. This Apple Store is mostly useless when you do not give it any credit card information – and I do not have one! And the Apple Store does not seem to sort the Xcode versions and show only the relevant one so that you can make mistakes and download a few unusable GB of a wrong version. One final step after installation is the activation of the command line tools and to accept some rules from Apple.

I have no knowledge of more restrictions…

—
Greetings

  Pete

If my theory of relativity is proven successful, Germany will claim me as a German, and France will declare that I am a citizen of the world. Should my theory prove untrue, France will say that I am a German, and Germany will declare that I am a Jew.
				– Albert Einstein, 1929

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

Since Apple is so nasty about its C compiler, let's urge MacOS users
to build Emacs with a free C compiler instead -- on principle.

Emacs still builds on MacOS with GCC, right?



-- 
Dr Richard Stallman
President, Free Software Foundation (https://gnu.org, https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)
Skype: No way! See https://stallman.org/skype.html.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Alan Third]

On Mon, Apr 09, 2018 at 10:35:49PM -0400, Richard Stallman wrote:
> Since Apple is so nasty about its C compiler, let's urge MacOS users
> to build Emacs with a free C compiler instead -- on principle.

FWIW, you don’t need to install XCode or even use the Apple App store
to install the XCode command line tools these days. It’s a simple
command line instruction.

> Emacs still builds on MacOS with GCC, right?

I don’t think Cocoa works with GCC, but building against GNUstep, or
using something other than --with-ns will be fine.
-- 
Alan Third

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Peter Dyballa]

> Am 10.4.2018 um 04:35 schrieb Richard Stallman <rms@gnu.org>:
> 
> Since Apple is so nasty about its C compiler, let's urge MacOS users
> to build Emacs with a free C compiler instead -- on principle.

Clang uses internally some GCC components. Its source code is freely available under the NCSA license (http://clang.llvm.org/, http://llvm.org/). And it's also the native compiler on Macs now. Without Xcode you cannot bootstrap GCC. Xcode is also needed for porting GNU Emacs to iPad or iPhone… (I presume)

And you don't have to pay for it – since decades. (Support will cost.)

> 
> Emacs still builds on MacOS with GCC, right?

Here is a first try to configure the NS variant of GNU Emacs 26.1-rc1 with GCC 7.3:

	checking for X... libraries /opt/local/lib, headers /opt/local/include
	checking AppKit/AppKit.h usability... no
	checking AppKit/AppKit.h presence... yes
	configure: WARNING: AppKit/AppKit.h: present but cannot be compiled
	configure: WARNING: AppKit/AppKit.h:     check for missing prerequisite headers?
	configure: WARNING: AppKit/AppKit.h: see the Autoconf documentation
	configure: WARNING: AppKit/AppKit.h:     section "Present But Cannot Be Compiled"
	configure: WARNING: AppKit/AppKit.h: proceeding with the compiler's result
	configure: WARNING:     ## ------------------------------------ ##
	configure: WARNING:     ## Report this to bug-gnu-emacs@gnu.org ##
	configure: WARNING:     ## ------------------------------------ ##
	checking for AppKit/AppKit.h... no
	configure: error: The include files (AppKit/AppKit.h etc) that
	are required for a Nextstep build are missing or cannot be compiled.
	Either fix this, or re-configure with the option '--without-ns'.

The same happens with GCC 5.5. With Clang 5.0 (not from Xcode) configuration does not abort here but comes to an end. The NS variant then builds and also runs as it does with Xcode's Clang 9.1.

Building the X client works with most if not all C compilers.

-rwxr-xr-x 1 root wheel 21577940 2018-04-10 21:09 /usr/local/bin/emacs-26.1 (NS) with Clang 5
-rwxr-xr-x 1 root wheel 21639508 2018-04-10 21:39 /usr/local/bin/emacs-26.1 (NS) with Clang 9

-rwxr-xr-x 1 root wheel 17198576 2018-04-10 21:53 /usr/local/bin/emacs-26.1 (Xaw3d) with GCC 7
-rwxr-xr-x 1 root wheel 17126304 2018-04-10 22:08 /usr/local/bin/emacs-26.1 (Xaw3d) with Clang 9

All run OK. For the moment.

(Xcode comes without gcc. It has symbolic-links cc and c++ both pointing to clang. And clang++ points to clang.)

—
Greetings

  Pete

It is so hot in some places that the people there have to live in other places.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > I don’t think Cocoa works with GCC,

Could you explain what that means?  What is "Cocoa"
and what does it mean for it to work, or not work, with GCC?

-- 
Dr Richard Stallman
President, Free Software Foundation (https://gnu.org, https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)
Skype: No way! See https://stallman.org/skype.html.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Peter Dyballa]

Am 12.4.2018 um 05:09 schrieb Richard Stallman <rms@gnu.org>:
> 
> Could you explain what that means?  What is "Cocoa"
> and what does it mean for it to work, or not work, with GCC?

It's in Objective-C/C++ (https://en.wikipedia.org/wiki/Objective-C) API from Apple, https://en.wikipedia.org/wiki/Cocoa_(API), kind of successor of NeXTSTEP. The NS variant of GNU Emacs has to use it to show up on screen.

—
Greetings

 Pete

One-Shot Case Study, n.:
	The scientific equivalent of the four-leaf clover, from which it is concluded all clovers possess four leaves and are sometimes green.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Alan Third]

On Wed, Apr 11, 2018 at 11:09:01PM -0400, Richard Stallman wrote:
> 
>   > I don’t think Cocoa works with GCC,
> 
> Could you explain what that means?  What is "Cocoa"
> and what does it mean for it to work, or not work, with GCC?

It’s Apple’s direct equivalent of GNUstep.

When I try to build Emacs with GCC it fails with the message

    configure: WARNING: AppKit/AppKit.h: present but cannot be
    compiled

If I try to compile this:

    #import <Appkit/Appkit.h>
    
    int main() {
      return 1;
    }

I get a massive list of errors using GCC, but clang compiles it
silently. I think it’s because Apple have made a number of
incompatible changes to their implementation of Objective‐C that
haven’t been replicated in GCC.

-- 
Alan Third

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Peter Dyballa]

> Am 13.4.2018 um 20:14 schrieb Alan Third <alan@idiocy.org>:
> 
> I think it’s because Apple have made a number of
> incompatible changes to their implementation of Objective‐C that
> haven’t been replicated in GCC.

I think the last version of GCC that could compile the NS variant was 4.2.1 (4.2.4 in the MacPorts package manager), "Apple augmented" to also be able to build those typical application bundles. And of course it was then the C compiler in Xcode. This was ten years ago, in 2007/2008. Xcode 3.2 from this time was the last release to rely completely on GCC, but also offered a version of LLVM-GCC. Xcode 4.0 from 2011 came with LLVM-GCC plus Clang, and an update to Xcode 4.2 came with ARC, Automatic Reference Counting. (Needed at least Mac OS X 10.7, Lion?) And I think Xcode 4 was available in Mac App Store for some money only…

I did not upgrade to Lion and newer versions for many years (I stayed with Leopard, Mac OS X 10.5.8, until last Christmas) and I still have some old configure logs. GCC 4.8, 5.3, and 6.x could successfully check AppKit.h usable (GNU Emacs 25.0.90/95), but they later failed with different errors; February and June 2016.

—

Greetings

  Pete

Upgraded, adj.:
	Didn't work the first time.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > I think the last version of GCC that could compile the NS variant
  > was 4.2.1 (4.2.4 in the MacPorts package manager), "Apple
  > augmented" to also be able to build those typical application
  > bundles.

This is a very bad situation.  I don't want to have code in Emacs that
can only be compiled with Clang, and I am determined to change that.
Will people please help me find the least disruptive way?

I would expect that most of the files of Emacs can compile with GCC
even on MacOS, but is that so?

What about with GNUstep?  Does Emacs compile for GCC with GNUstep?

-- 
Dr Richard Stallman
President, Free Software Foundation (https://gnu.org, https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)
Skype: No way! See https://stallman.org/skype.html.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

      > #import <Appkit/Appkit.h>

Which files in Emacs include that header?

-- 
Dr Richard Stallman
President, Free Software Foundation (https://gnu.org, https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)
Skype: No way! See https://stallman.org/skype.html.

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Peter Dyballa]

> Am 16.4.2018 um 05:14 schrieb Richard Stallman <rms@gnu.org>:
> 
> I don't want to have code in Emacs that
> can only be compiled with Clang, and I am determined to change that.

Bad idea, IMO.

—
Greetings

  Pete

"Free markets would be a great idea, if markets were actually free."

bug#30992: Acknowledgement (27.0.50; Crash when graphics card switches)

[Alan Third]

On Sun, Apr 15, 2018 at 11:14:48PM -0400, Richard Stallman wrote:
> > #import <Appkit/Appkit.h>
> 
> Which files in Emacs include that header?

nsgui.h, and configure must reference it in its tests too.

It’s required for both GNUstep and Cocoa.

>   > I think the last version of GCC that could compile the NS variant
>   > was 4.2.1 (4.2.4 in the MacPorts package manager), "Apple
>   > augmented" to also be able to build those typical application
>   > bundles.
> 
> This is a very bad situation.  I don't want to have code in Emacs that
> can only be compiled with Clang, and I am determined to change that.
> Will people please help me find the least disruptive way?
> 
> I would expect that most of the files of Emacs can compile with GCC
> even on MacOS, but is that so?

As far as I’m aware there is no code in Emacs itself that requires
Clang. There were a couple of Objective‐C ‘blocks’ that we removed
previously as GCC doesn’t support them.

I don’t know how we would get to a position of being able to build
with GCC and Cocoa. I assume GCC would have to support some or all of
the Obj‐C features it’s currently missing.

> What about with GNUstep?  Does Emacs compile for GCC with GNUstep?

Yes. My test‐build VM uses GCC 4.9.2 which compiles GNUstep Emacs
fine.
-- 
Alan Third