CC Mode: allow specified directives (e.g. pragma) to be indented as statements

* lisp/progmodes/cc-cmds.el (c-align-cpp-indent-to-body)
(c-cpp-indent-to-body-flag, c-electric-pragma)
(c-add-indent-to-body-to-abbrev-table, c-clear-stale-indent-to-body-abbrevs)
(c-toggle-cpp-indent-to-body): New functions and variables.

* lisp/progmodes/cc-langs.el (c-std-abbrev-keywords): New lang const/var.

* lisp/progmodes/cc-mode.el (c-populate-abbrev-table): New function.
(c-basic-common-init): call the c-populate-abbrev-table.
(c-mode, c++-mode, objc-mode, java-mode, idl-mode, pike-mode, awk-mode):
Remove the setting of MODE-abbrev-table.

* lisp/progmodes/cc-vars.el (c-cpp-indent-to-body-directives): New defcustom.

* doc/misc/cc-mode.texi (Custom Macros): Introduce and refer to ....
(Indenting Directives): New page documenting the new mechanism.

1 files changed, 93 insertions, 0 deletions

diff --git a/lisp/progmodes/cc-cmds.el b/lisp/progmodes/cc-cmds.el
index a60812230b8..1b557c41a5d 100644
--- a/lisp/progmodes/cc-cmds.el
+++ b/lisp/progmodes/cc-cmds.el
@@ -48,6 +48,7 @@
 (cc-bytecomp-defvar filladapt-mode)	; c-fill-paragraph contains a kludge
 					; which looks at this.
 (cc-bytecomp-defun electric-pair-post-self-insert-function)
+(cc-bytecomp-defvar c-indent-to-body-directives)
 
 ;; Indentation / Display syntax functions
 (defvar c-fix-backslashes t)
@@ -1441,6 +1442,98 @@ keyword on the line, the keyword is not inserted inside a literal, and
 	  (indent-according-to-mode)
 	(delete-char -2)))))
 
+(defun c-align-cpp-indent-to-body ()
+  "Align a \"#pragma\" line under the previous line.
+This function is intented for use as a member of `c-special-indent-hook'."
+  (when (assq 'cpp-macro c-syntactic-context)
+    (when
+	(save-excursion
+	  (save-match-data
+	    (back-to-indentation)
+	    (and
+	     (looking-at (concat c-opt-cpp-symbol "[ \t]*\\([a-zA-Z0-9_]+\\)"))
+	     (member (match-string-no-properties 1)
+		     c-cpp-indent-to-body-directives))))
+      (c-indent-line (delete '(cpp-macro) c-syntactic-context)))))
+
+(defvar c-cpp-indent-to-body-flag nil)
+;; Non-nil when CPP directives such as "#pragma" should be indented to under
+;; the preceding statement.
+(make-variable-buffer-local 'c-cpp-indent-to-body-flag)
+
+(defun c-electric-pragma ()
+  "Reindent the current line if appropriate.
+
+This function is used to reindent a preprocessor line when the
+symbol for the directive, typically \"pragma\", triggers this
+function as a hook function of an abbreviation.
+
+The \"#\" of the preprocessor construct is aligned under the
+first anchor point of the line's syntactic context.
+
+The line is reindented if the construct is not in a string or
+comment, there is exactly one \"#\" contained in optional
+whitespace before it on the current line, and `c-electric-flag'
+and `c-syntactic-indentation' are both non-nil."
+  (save-excursion
+    (save-match-data
+      (when
+	  (and
+	   c-cpp-indent-to-body-flag
+	   c-electric-flag
+	   c-syntactic-indentation
+	   last-abbrev-location
+	   c-opt-cpp-symbol		; "#" or nil.
+	   (progn (back-to-indentation)
+		  (looking-at (concat c-opt-cpp-symbol "[ \t]*")))
+	   (>= (match-end 0) last-abbrev-location)
+	   (not (c-literal-limits)))
+	(c-indent-line (delete '(cpp-macro) (c-guess-basic-syntax)))))))
+
+(defun c-add-indent-to-body-to-abbrev-table (d)
+  ;; Create an abbreviation table entry for the directive D, and add it to the
+  ;; current abbreviation table.  Existing abbreviation (e.g. for "else") do
+  ;; not get overwritten.
+  (when (and c-buffer-is-cc-mode
+	     local-abbrev-table
+	     (not (abbrev-symbol d local-abbrev-table)))
+    (condition-case nil
+	(define-abbrev local-abbrev-table d d 'c-electric-pragma 0 t)
+      (wrong-number-of-arguments
+       (define-abbrev local-abbrev-table d d 'c-electric-pragma)))))
+
+(defun c-clear-stale-indent-to-body-abbrevs ()
+  ;; Fill in this comment.  FIXME!!!
+  (when (fboundp 'abbrev-get)
+    (mapatoms (lambda (a)
+		(when (and (abbrev-get a ':system) ; Preserve a user's abbrev!
+			   (not (member (symbol-name a) c-std-abbrev-keywords))
+			   (not (member (symbol-name a)
+					c-cpp-indent-to-body-directives)))
+		  (unintern a local-abbrev-table)))
+	      local-abbrev-table)))
+
+(defun c-toggle-cpp-indent-to-body (&optional arg)
+  "Toggle the C preprocessor indent-to-body feature.
+When enabled, preprocessor directives which are words in
+`c-indent-to-body-directives' are indented as if they were statements.
+
+Optional numeric ARG, if supplied, turns on the feature when positive,
+turns it off when negative, and just toggles it when zero or
+left out."
+  (interactive "P")
+  (setq c-cpp-indent-to-body-flag
+	(c-calculate-state arg c-cpp-indent-to-body-flag))
+  (if c-cpp-indent-to-body-flag
+      (progn
+	(c-clear-stale-indent-to-body-abbrevs)
+	(mapc 'c-add-indent-to-body-to-abbrev-table
+	      c-cpp-indent-to-body-directives)
+	(add-hook 'c-special-indent-hook 'c-align-cpp-indent-to-body nil t))
+    (remove-hook 'c-special-indent-hook 'c-align-cpp-indent-to-body t))
+  (message "c-cpp-indent-to-body %sabled"
+	   (if c-cpp-indent-to-body-flag "en" "dis")))
+
 
 
 (declare-function subword-forward "subword" (&optional arg))