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, 8 insertions, 0 deletions

diff --git a/etc/DEBUG b/etc/DEBUG
index aeb447bae33..19c75e81ada 100644
--- a/etc/DEBUG
+++ b/etc/DEBUG
@@ -78,6 +78,14 @@ described in the node "Auto-loading safe path" in the GDB user manual.
 If nothing else helps, type "source /path/to/.gdbinit RET" at the GDB
 prompt, to unconditionally load the GDB init file.
 
+Running GDB on macOS sometimes brings an error message like this:
+
+  Unable to find Mach task port for process-id NNN: (os/kern) failure (0x5).
+
+To overcome this, search the Internet for the phrase "Unable to find
+Mach task port for process-id", and you will find detailed
+instructions to follow.
+
 *** Use the Emacs GDB UI front-end
 
 We recommend using the GUI front-end for GDB provided by Emacs.  With