[Bug-AUCTeX] auctex + XeTeX (XeLaTeX) crash with emacs 23.4

[Jose Gosdin]

Auctex causes emacs 23.4 to hang when TeX-engine is set to xelatex.

Steps to reproduce:

$ emacs -Q /tmp/blankfile.tex

Load auctex and evaluate:

(setq TeX-engine 'xelatex)
(setq TeX-PDF-mode t)

C and elisp backtrace:

(gdb) run -Q /tmp/tex.tex
Starting program: /tmp/emacs-23.4/src/emacs -Q /tmp/tex.tex
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/libthread_db.so.1".

Program received signal SIGTSTP, Stopped (user).
re_match_2_internal (bufp=0xbc5888, string1=0x0, size1=0,
string2=0x16c2338 "%(latex) %S%(PDFout)%(mode)%' %t",
    size2=32, pos=0, regs=0xbb64e0, stop=32) at regex.c:6392
6392          continue;  /* Successfully executed one pattern command;
keep going.  */
(gdb) backtrace
#0  re_match_2_internal (bufp=0xbc5888, string1=0x0, size1=0,
string2=0x16c2338 "%(latex) %S%(PDFout)%(mode)%' %t",
    size2=32, pos=0, regs=0xbb64e0, stop=32) at regex.c:6392
#1  0x00000000005be353 in re_search_2 (bufp=0xbc5888, str1=0x0, size1=0,
    str2=0x16c2338 "%(latex) %S%(PDFout)%(mode)%' %t", size2=32,
startpos=0, range=32, regs=0xbb64e0, stop=32)
    at regex.c:4627
#2  0x00000000005bd421 in re_search (bufp=0xbc5888, string=0x16c2338
"%(latex) %S%(PDFout)%(mode)%' %t", size=32,
    startpos=0, range=32, regs=0xbb64e0) at regex.c:4399
#3  0x00000000005a992d in string_match_1 (regexp=24015633,
string=24015249, start=0, posix=0) at search.c:439
#4  0x00000000005a9a9f in Fstring_match (regexp=24015633,
string=24015249, start=0) at search.c:480
#5  0x00000000005ed56a in Ffuncall (nargs=4, args=0x7fffffffccd0) at eval.c:3037
#6  0x000000000063b46b in Fbyte_code (bytestr=23984609,
vector=23987973, maxdepth=56) at bytecode.c:683
#7  0x00000000005ede43 in funcall_lambda (fun=23988533, nargs=2,
arg_vector=0x7fffffffd188) at eval.c:3220
#8  0x00000000005ed73b in Ffuncall (nargs=3, args=0x7fffffffd180) at eval.c:3077
#9  0x000000000063b46b in Fbyte_code (bytestr=23982817,
vector=23984917, maxdepth=24) at bytecode.c:683
#10 0x00000000005ede43 in funcall_lambda (fun=23985317, nargs=3,
arg_vector=0x7fffffffd5f8) at eval.c:3220
#11 0x00000000005ed73b in Ffuncall (nargs=4, args=0x7fffffffd5f0) at eval.c:3077
#12 0x000000000063b46b in Fbyte_code (bytestr=23964097,
vector=23965141, maxdepth=16) at bytecode.c:683
#13 0x00000000005ede43 in funcall_lambda (fun=23965413, nargs=1,
arg_vector=0x7fffffffdaa8) at eval.c:3220
#14 0x00000000005ed73b in Ffuncall (nargs=2, args=0x7fffffffdaa0) at eval.c:3077
#15 0x00000000005e7e6c in Fcall_interactively (function=15260706,
record_flag=12427826, keys=12486341)
    at callint.c:869
#16 0x00000000005ed56a in Ffuncall (nargs=4, args=0x7fffffffde40) at eval.c:3037
#17 0x00000000005ecf6f in call3 (fn=12615874, arg1=15260706,
arg2=12427826, arg3=12427826) at eval.c:2857
---Type <return> to continue, or q <return> to quit---
#18 0x0000000000560c69 in Fcommand_execute (cmd=15260706,
record_flag=12427826, keys=12427826, special=12427826)
    at keyboard.c:10563
#19 0x000000000054f601 in command_loop_1 () at keyboard.c:1907
#20 0x00000000005ea5e7 in internal_condition_case (bfun=0x54dc5f
<command_loop_1>, handlers=12495090,
    hfun=0x54d554 <cmd_error>) at eval.c:1492
#21 0x000000000054d95d in command_loop_2 () at keyboard.c:1363
#22 0x00000000005e9f83 in internal_catch (tag=12487906, func=0x54d93b
<command_loop_2>, arg=12427826) at eval.c:1228
#23 0x000000000054d912 in command_loop () at keyboard.c:1342
#24 0x000000000054d088 in recursive_edit_1 () at keyboard.c:957
#25 0x000000000054d23e in Frecursive_edit () at keyboard.c:1019
#26 0x000000000054b567 in main (argc=3, argv=0x7fffffffe848) at emacs.c:1838

Lisp Backtrace:
"string-match" (0xffffccd8)
"TeX-command-expand" (0xffffd188)
"TeX-command" (0xffffd5f8)
"TeX-command-master" (0xffffdaa8)
"call-interactively" (0xffffde48)
(gdb)

XeLaTeX version:

$ xelatex
This is XeTeX, Version 3.1415926-2.3-0.9997.5 (TeX Live 2012/dev/Arch Linux)