1 files changed, 45 insertions, 0 deletions
diff --git a/lisp/cmacexp.el b/lisp/cmacexp.el
new file mode 100644
index 00000000000..7b33282bb88
--- /dev/null
+++ b/lisp/cmacexp.el
@@ -0,0 +1,45 @@
+
+(defun c-macro-expand (beg end)
+  "Display the result of expanding all C macros occurring in the region.
+The expansion is entirely correct because it uses the C preprocessor."
+  (interactive "r")
+  (let ((outbuf (get-buffer-create "*Macroexpansion*"))
+	(tempfile "%%macroexpand%%")
+	process
+	last-needed)
+    (save-excursion
+      (set-buffer outbuf)
+      (erase-buffer))
+    (setq process (start-process "macros" outbuf "/lib/cpp"))
+    (set-process-sentinel process '(lambda (&rest x)))
+    (save-restriction
+      (widen)
+      (save-excursion
+	(goto-char beg)
+	(beginning-of-line)
+	(setq last-needed (point))
+	(if (re-search-backward "^[ \t]*#" nil t)
+	    (progn
+	      ;; Skip continued lines.
+	      (while (progn (end-of-line) (= (preceding-char) ?\\))
+		(forward-line 1))
+	      ;; Skip the last line of the macro definition we found.
+	      (forward-line 1)
+	      (setq last-needed (point)))))
+      (write-region (point-min) last-needed tempfile nil 'nomsg)
+      (process-send-string process (concat "#include \"" tempfile "\"\n"))
+      (process-send-string process "\n")
+      (process-send-region process beg end)
+      (process-send-string process "\n")
+      (process-send-eof process))
+    (while (eq (process-status process) 'run)
+      (accept-process-output))
+    (delete-file tempfile)
+    (save-excursion
+      (set-buffer outbuf)
+      (goto-char (point-max))
+      (re-search-backward "\n# [12] \"\"")
+      (forward-line 2)
+      (while (eolp) (delete-char 1))
+      (delete-region (point-min) (point)))
+    (display-buffer outbuf)))