Merge from origin/emacs-26

1d732d6 (origin/emacs-26) Fix gud-statement for pdb
91a68b5 ; * msdos/INSTALL: Add info about GCC versions.
7ddcc9a Document 'custom-group'
58f9e15 A minor addition to etc/DEBUG
4590414 Avoid errors in ispell.el when Enchant returns empty extra chars
d0d75f9 Make 'ispell-initialize-spellchecker-hook' work again
b90ce66 Handle selected_window change in prepare_menu_bars (Bug#31312)
79ad0b3 ; * INSTALL: Fix Emacs version number.  (Bug#31358)
91de88b Fix report-emacs-bug via mailclient on MS-Windows
f4b5ff2 Port collation tests to glibc 2.27

1 files changed, 12 insertions, 3 deletions

diff --git a/msdos/INSTALL b/msdos/INSTALL
index 3b343f14563..3707f436625 100644
--- a/msdos/INSTALL
+++ b/msdos/INSTALL
@@ -19,6 +19,15 @@ the necessary utilities; search for "MS-DOS".  The configuration step
 (see below) will test for these utilities and will refuse to continue
 if any of them isn't found.
 
+You should carefully choose the version of GCC you use to build Emacs,
+because recent versions of GCC don't support building Emacs very well.
+The main issue is the debug info: the DJGPP build of Emacs must use
+the COFF debug info.  GCC support for COFF debug info was steadily
+deteriorating since GCC 5, and GCC 8.1 officially stopped supporting
+the -gcoff switch, which the Emacs build process needs.  We recommend
+using GCC 3.4.X and Binutils 2.26; GDB 7.2 is capable to debug an
+Emacs binary built by this combination.
+
 Bootstrapping Emacs or recompiling Lisp files in the `lisp'
 subdirectory using the various targets in the lisp/Makefile file
 requires additional utilities: `find' (from Findutils), GNU `echo' and
@@ -70,15 +79,15 @@ Running "config msdos" checks for several programs that are required
 to configure and build Emacs; if one of those programs is not found,
 CONFIG.BAT stops and prints an error message.
 
-On Windows NT and Windows 2000/XP/Vista/7, running "config msdos"
+On Windows NT and Windows 2000/XP and later, running "config msdos"
 might print an error message like "VDM has been already loaded".  This
 is because those systems have a program called `redir.exe' which is
 incompatible with a program by the same name supplied with DJGPP,
 which is used by config.bat.  To resolve this, move the DJGPP's `bin'
 subdirectory to the front of your PATH environment variable.
 
-Windows Vista/7 has several bugs in its DPMI server related to memory
-allocation: it fails DPMI resize memory block function, and it
+Windows Vista and later has several bugs in its DPMI server related to
+memory allocation: it fails DPMI resize memory block function, and it
 arbitrarily limits the default amount of DPMI memory to 32MB.  To work
 around these bugs, first configure Emacs to use the `malloc' function
 from the DJGPP library.  To this end, run CONFIG.BAT with the