Function: c-macro-expansion
c-macro-expansion is a byte-compiled function defined in
cmacexp.el.gz.
Signature
(c-macro-expansion START END CPPCOMMAND &optional DISPLAY)
Documentation
Run a preprocessor on region and return the output as a string.
Expand the region between START and END in the current buffer using the shell command CPPCOMMAND (e.g. "/lib/cpp -C -DDEBUG"). Be sure to use a -C (don't strip comments) or equivalent option. Optional arg DISPLAY non-nil means show messages in the echo area.
Source Code
;; Defined in /usr/src/emacs/lisp/progmodes/cmacexp.el.gz
(defun c-macro-expansion (start end cppcommand &optional display)
"Run a preprocessor on region and return the output as a string.
Expand the region between START and END in the current buffer using
the shell command CPPCOMMAND (e.g. \"/lib/cpp -C -DDEBUG\").
Be sure to use a -C (don't strip comments) or equivalent option.
Optional arg DISPLAY non-nil means show messages in the echo area."
;; Copy the current buffer's contents to a temporary hidden buffer.
;; Delete from END to end of buffer. Insert a preprocessor #line
;; directive at START and after each #endif following START that are
;; not inside a comment or a string. Put all the strings thus
;; inserted (without the "line" substring) in a list named linelist.
;; If START is inside a comment, prepend "*/" and append "/*" to the
;; #line directive. If inside a string, prepend and append "\"".
;; Preprocess the buffer contents, then look for all the lines stored
;; in linelist starting from end of buffer. The last line so found is
;; where START was, so return the substring from point to end of
;; buffer.
(let ((inbuf (current-buffer))
(outbuf (get-buffer-create " *C Macro Expansion*"))
(filename (if (and buffer-file-name
(string-match (regexp-quote default-directory)
buffer-file-name))
(substring buffer-file-name (match-end 0))
(buffer-name)))
(mymsg (format "Invoking %s%s%s on region..."
c-macro-preprocessor
(if (string= "" c-macro-cppflags) "" " ")
c-macro-cppflags))
(uniquestring "??? !!! ??? start of c-macro expansion ??? !!! ???")
(startlinenum 0)
(linenum 0)
(startstat ())
(startmarker "")
(exit-status 0)
(tempname (make-temp-file
(expand-file-name "cmacexp"
(or small-temporary-file-directory
temporary-file-directory)))))
(unwind-protect
(save-excursion
(save-restriction
(widen)
(let ((in-syntax-table (syntax-table)))
(set-buffer outbuf)
(setq buffer-read-only nil)
(erase-buffer)
(set-syntax-table in-syntax-table))
(insert-buffer-substring inbuf 1 end))
;; We have copied inbuf to outbuf. Point is at end of
;; outbuf. Inset a newline at the end, so cpp can correctly
;; parse a token ending at END.
(insert "\n")
;; Save sexp status and line number at START.
(setq startstat (parse-partial-sexp 1 start))
(setq startlinenum (+ (count-lines 1 (point))
(if (bolp) 1 0)))
;; Now we insert the #line directives after all #endif or
;; #else following START going backward, so the lines we
;; insert don't change the line numbers.
;(switch-to-buffer outbuf) (debug) ;debugging instructions
(goto-char (point-max))
(while (re-search-backward "\n#\\(endif\\|else\\)\\>" start 'move)
(if (equal (nthcdr 3 (parse-partial-sexp start (point)
nil nil startstat))
'(nil nil nil 0 nil)) ;neither in string nor in
;comment nor after quote
(progn
(goto-char (match-end 0))
(setq linenum (+ startlinenum
(count-lines start (point))))
(insert (format "\n#line %d \"%s\"\n" linenum filename))
(goto-char (match-beginning 0)))))
;; Now we are at START. Insert the first #line directive.
;; This must work even inside a string or comment, or after a
;; quote.
(let* ((startinstring (nth 3 startstat))
(startincomment (nth 4 startstat))
(startafterquote (nth 5 startstat))
(startinbcomment (nth 7 startstat)))
(insert (if startafterquote " " "")
(cond (startinstring
(char-to-string startinstring))
(startincomment "*/")
(""))
(setq startmarker
(concat "\n" uniquestring
(cond (startinstring
(char-to-string startinstring))
(startincomment "/*")
(startinbcomment "//"))
(if startafterquote "\\")))
(format "\n#line %d \"%s\"\n" startlinenum filename)))
;; Call the preprocessor.
(if display (message "%s" mymsg))
(setq exit-status
(call-process-region 1 (point-max)
shell-file-name
t (list t tempname) nil "-c"
cppcommand))
(if display (message "%s" (concat mymsg "done")))
(if (= (buffer-size) 0)
;; Empty output is normal after a fatal error.
(insert "\nPreprocessor produced no output\n")
;; Find and delete the mark of the start of the expansion.
;; Look for `# nn "file.c"' lines and delete them.
(goto-char (point-min))
(if (search-forward startmarker nil t)
(delete-region 1 (point))))
(while (re-search-forward (concat "^# [0-9]+ \""
(regexp-quote filename)
"\"") nil t)
(beginning-of-line)
(let ((beg (point)))
(forward-line 1)
(delete-region beg (point))))
;; If CPP got errors, show them at the beginning.
;; MS-DOS shells don't return the exit code of their children.
;; Look at the size of the error message file instead, but
;; don't punish those MS-DOS users who have a shell that does
;; return an error code.
(or (and (or (not (boundp 'msdos-shells))
(not (member (file-name-nondirectory shell-file-name)
msdos-shells)))
(eq exit-status 0))
(zerop (file-attribute-size
(file-attributes (expand-file-name tempname))))
(progn
(goto-char (point-min))
;; Put the messages inside a comment, so they won't get in
;; the way of font-lock, highlighting etc.
(insert
(format
"/* Preprocessor terminated with status %s\n\n Messages from '%s':\n\n"
exit-status cppcommand))
(goto-char (+ (point)
(nth 1 (insert-file-contents tempname))))
(insert "\n\n*/\n")))
(delete-file tempname)
;; Compute the return value, keeping in account the space
;; inserted at the end of the buffer.
(buffer-substring 1 (max 1 (- (point-max) 1))))
;; Cleanup.
(kill-buffer outbuf))))