Hi,
I prefer xetex as my default tex engine. But this will cause a AucTeX
bug when the master filename contains a space.

The following is a minimal example. It contains only one master file "foo
bar.tex". Notice the filename contains a space. And the content of "foo
bar.tex" is just the following:

\documentclass{article}
\begin{document}
Hello world
\end{document}
%%% Local Variables:
%%% mode: latex
%%% TeX-master: t
%%% TeX-engine: xetex
%%% End:

Now if press C-c C-c to compile this file. AucTeX will return the
following error message:

Running `LaTeX' on `foo bar' with ``xelatex  -file-line-error  --synctex=1
-interaction=nonstopmode "\input" ^"\^"foo bar.tex\^"^"''
This is XeTeX, Version 3.14159265-2.6-0.99996 (TeX Live 2016/W32TeX)
(preloaded format=xelatex)
 restricted \write18 enabled.
entering extended mode
LaTeX2e <2016/03/31> patch level 3
Babel <3.9r> and hyphenation patterns for 83 language(s) loaded.
! I can't find file `'"foo bar.tex"''.
<*> \input '"foo bar.tex"'

(Press Enter to retry, or Control-Z to exit)
Please type another input file name
! Emergency stop.
<*> \input '"foo bar.tex"'

If I switch my tex engine to pdflatex, then this problem will
gone. Moreover, if run the following command in a terminal

  xelatex --file-line-error --synctex=1 -interaction=nonstopmode "\input"
"foo bar.tex"

Then it also works well. So I assume this is a AucTeX bug.

Best,
Qiang


Emacs  : GNU Emacs 25.1.1 (x86_64-w64-mingw32)
 of 2016-09-18
Package: 11.89.8

current state:
==============
(setq
 AUCTeX-date "2016-12-22"
 window-system 'w32
 LaTeX-version "2e"
 TeX-style-path '("~/.emacs.d/auctex"
                  "d:/Home/.emacs.d/elpa/auctex-11.89.8/style"
                  "d:/Home/.emacs.d/auctex/auto"
                  "d:/Home/.emacs.d/auctex/style" "auto" "style")
 TeX-auto-save t
 TeX-parse-self t
 TeX-master t
 TeX-command-list '(("TeX"
                     "%(PDF)%(tex) %(file-line-error) %(extraopts)
%`%S%(PDFout)%(mode)%' %t"
                     TeX-run-TeX nil
                     (plain-tex-mode ams-tex-mode texinfo-mode) :help
                     "Run plain TeX")
                    ("LaTeX" "%`%l%(mode)%' %t" TeX-run-TeX nil
                     (latex-mode doctex-mode) :help "Run LaTeX")
                    ("Makeinfo" "makeinfo %(extraopts) %t" TeX-run-compile
                     nil (texinfo-mode) :help
                     "Run Makeinfo with Info output")
                    ("Makeinfo HTML" "makeinfo %(extraopts) --html %t"
                     TeX-run-compile nil (texinfo-mode) :help
                     "Run Makeinfo with HTML output")
                    ("AmSTeX"
                     "amstex %(PDFout) %(extraopts) %`%S%(mode)%' %t"
                     TeX-run-TeX nil (ams-tex-mode) :help "Run AMSTeX")
                    ("ConTeXt"
                     "%(cntxcom) --once --texutil %(extraopts)
%(execopts)%t"
                     TeX-run-TeX nil (context-mode) :help
                     "Run ConTeXt once")
                    ("ConTeXt Full" "%(cntxcom) %(extraopts) %(execopts)%t"
                     TeX-run-TeX nil (context-mode) :help
                     "Run ConTeXt until completion")
                    ("BibTeX" "bibtex %s" TeX-run-BibTeX nil t :help
                     "Run BibTeX")
                    ("Biber" "biber %s" TeX-run-Biber nil t :help
                     "Run Biber")
                    ("View" "%V" TeX-run-discard-or-function t t :help
                     "Run Viewer")
                    ("Print" "%p" TeX-run-command t t :help
                     "Print the file")
                    ("Queue" "%q" TeX-run-background nil t :help
                     "View the printer queue" :visible TeX-queue-command)
                    ("File" "%(o?)dvips %d -o %f " TeX-run-dvips t t :help
                     "Generate PostScript file")
                    ("Dvips" "%(o?)dvips %d -o %f " TeX-run-dvips nil t
                     :help "Convert DVI file to PostScript")
                    ("Dvipdfmx" "dvipdfmx %d" TeX-run-dvipdfmx nil t :help
                     "Convert DVI file to PDF with dvipdfmx")
                    ("Ps2pdf" "ps2pdf %f" TeX-run-ps2pdf nil t :help
                     "Convert PostScript file to PDF")
                    ("Index" "makeindex %s" TeX-run-index nil t :help
                     "Run makeindex to create index file")
                    ("Xindy" "texindy %s" TeX-run-command nil t :help
                     "Run xindy to create index file")
                    ("Check" "lacheck %s" TeX-run-compile nil (latex-mode)
                     :help "Check LaTeX file for correctness")
                    ("ChkTeX" "chktex -v6 %s" TeX-run-compile nil
                     (latex-mode) :help
                     "Check LaTeX file for common mistakes")
                    ("Spell" "(TeX-ispell-document \"\")" TeX-run-function
                     nil t :help "Spell-check the document")
                    ("Clean" "TeX-clean" TeX-run-function nil t :help
                     "Delete generated intermediate files")
                    ("Clean All" "(TeX-clean t)" TeX-run-function nil t
                     :help "Delete generated intermediate and output files")
                    ("Other" "" TeX-run-command t t :help
                     "Run an arbitrary command")
                    )
 )