Avoid crashes at startup on systems that CANNOT_DUMP

* src/xdisp.c (syms_of_xdisp) <redisplay--inhibit-bidi>: New
boolean variable.
(init_iterator, reseat_to_string)
(Fcurrent_bidi_paragraph_direction)
(Fbidi_find_overridden_directionality): Use
redisplay--inhibit-bidi instead of purify-flag, to determine when
it's safe to reorder bidirectional text.

* lisp/loadup.el (redisplay--inhibit-bidi): Set to t at the
beginning of the file.  Reset to nil when charprop.el is
successfully loaded, or when we are going to dump, whichever
happens last.  (Bug#22975)

1 files changed, 12 insertions, 1 deletions

diff --git a/lisp/loadup.el b/lisp/loadup.el
index b620e657223..bd47bed3160 100644
--- a/lisp/loadup.el
+++ b/lisp/loadup.el
@@ -47,6 +47,13 @@
 
 ;;; Code:
 
+;; This is used in xdisp.c to determine when bidi reordering is safe.
+;; (It starts non-nil in temacs, but we set it non-nil here anyway, in
+;; case someone loads loadup one more time.)  We reset it after
+;; successfully loading charprop.el, which defines the Unicode tables
+;; bidi.c needs for its job.
+(setq redisplay--inhibit-bidi t)
+
 ;; Add subdirectories to the load-path for files that might get
 ;; autoloaded when bootstrapping.
 ;; This is because PATH_DUMPLOADSEARCH is just "../lisp".
@@ -162,7 +169,8 @@
 (load "case-table")
 ;; This file doesn't exist when building a development version of Emacs
 ;; from the repository.  It is generated just after temacs is built.
-(load "international/charprop.el" t)
+(if (load "international/charprop.el" t)
+    (setq redisplay--inhibit-bidi nil))
 (load "international/characters")
 (load "composite")
 
@@ -415,6 +423,9 @@ lost after dumping")))
 (if (null (garbage-collect))
     (setq pure-space-overflow t))
 
+;; Make sure we will attempt bidi reordering henceforth.
+(setq redisplay--inhibit-bidi nil)
+
 (if (member (car (last command-line-args)) '("dump" "bootstrap"))
     (progn
       (message "Dumping under the name emacs")