Allow compilation during loading of Modes derived from a CC Mode mode.

Fixes debbugs#19206.

cc-bytecomp.el (cc-bytecomp-compiling-or-loading): new function which
walks the stack to discover whether we're compiling or loading.
(cc-bytecomp-is-compiling): Reformulate, and move towards beginning.
(cc-bytecomp-is-loading): New defsubst.
(cc-bytecomp-setup-environment, cc-bytecomp-restore-environment): Use
the
above defsubsts.
(cc-require-when-compile, cc-bytecomp-defvar)
(cc-bytecomp-defun): Simplify conditionals.

cc-defs.el (cc-bytecomp-compiling-or-loading): "Borrow" this function
from cc-bytecomp.el.
(c-get-current-file): Reformulate using the above.
(c-lang-defconst): Prevent duplicate entries of file names in a symbol's
'source property.
(c-lang-const): Use cc-bytecomp-is-compiling.

cc-langs.el (c-make-init-lang-vars-fun): Use cc-bytecomp-is-compiling.

4 files changed, 108 insertions, 38 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 532a10a1b71..072af5b1b91 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,29 @@
+2015-01-13  Alan Mackenzie  <acm@muc.de>
+
+        Allow compilation during loading of Modes derived from a CC Mode mode.
+        Fixes debbugs#19206.
+
+        * progmodes/cc-bytecomp.el (cc-bytecomp-compiling-or-loading): new
+        function which walks the stack to discover whether we're compiling
+        or loading.
+        (cc-bytecomp-is-compiling): Reformulate, and move towards
+        beginning.
+        (cc-bytecomp-is-loading): New defsubst.
+        (cc-bytecomp-setup-environment, cc-bytecomp-restore-environment):
+        Use the above defsubsts.
+        (cc-require-when-compile, cc-bytecomp-defvar)
+        (cc-bytecomp-defun): Simplify conditionals.
+
+        * progmodes/cc-defs.el (cc-bytecomp-compiling-or-loading):
+        "Borrow" this function from cc-bytecomp.el.
+        (c-get-current-file): Reformulate using the above.
+        (c-lang-defconst): Prevent duplicate entries of file names in a
+        symbol's 'source property.
+        (c-lang-const): Use cc-bytecomp-is-compiling.
+
+        * progmodes/cc-langs.el (c-make-init-lang-vars-fun): Use
+        cc-bytecomp-is-compiling.
+
 2015-01-13  Stefan Monnier  <monnier@iro.umontreal.ca>
 
         * emacs-lisp/eieio-core.el (eieio-defclass): Fix call to `defclass'
diff --git a/lisp/progmodes/cc-bytecomp.el b/lisp/progmodes/cc-bytecomp.el
index bf7803c85ca..b63eeb4c7a6 100644
--- a/lisp/progmodes/cc-bytecomp.el
+++ b/lisp/progmodes/cc-bytecomp.el
@@ -89,13 +89,60 @@
   ;;`(message ,@args)
   )
 
+(defun cc-bytecomp-compiling-or-loading ()
+  ;; Determine whether byte-compilation or loading is currently active,
+  ;; returning 'compiling, 'loading or nil.
+  ;; If both are active, the "innermost" activity counts.  Note that
+  ;; compilation can trigger loading (various `require' type forms)
+  ;; and loading can trigger compilation (the package manager does
+  ;; this).  We walk the lisp stack if necessary.
+  (cond
+   ((and load-in-progress
+         (boundp 'byte-compile-dest-file)
+         (stringp byte-compile-dest-file))
+    (let ((n 0) elt)
+      (while (and
+              (setq elt (backtrace-frame n))
+              (not (and (car elt)
+                        (memq (cadr elt)
+                              '(load require
+                                byte-compile-file byte-recompile-directory
+                                batch-byte-compile)))))
+        (setq n (1+ n)))
+      (cond
+       ((memq (cadr elt) '(load require))
+        'loading)
+       ((memq (cadr elt) '(byte-compile-file
+                           byte-recompile-directory
+                           batch-byte-compile))
+        'compiling)
+       (t                               ; Can't happen.
+        (message "cc-bytecomp-compiling-or-loading: System flags spuriously set")
+        nil))))
+   (load-in-progress
+    ;; Being loaded.
+    'loading)
+   ((and (boundp 'byte-compile-dest-file)
+         (stringp byte-compile-dest-file))
+    ;; Being compiled.
+    'compiling)
+   (t
+    ;; Being evaluated interactively.
+    nil)))
+
+(defsubst cc-bytecomp-is-compiling ()
+  "Return non-nil if eval'ed during compilation."
+  (eq (cc-bytecomp-compiling-or-loading) 'compiling))
+
+(defsubst cc-bytecomp-is-loading ()
+  "Return non-nil if eval'ed during loading.
+Nil will be returned if we're in a compilation triggered by the loading."
+  (eq (cc-bytecomp-compiling-or-loading) 'loading))
+
 (defun cc-bytecomp-setup-environment ()
   ;; Eval'ed during compilation to setup variables, functions etc
   ;; declared with `cc-bytecomp-defvar' et al.
-  (if (not load-in-progress)
-      ;; Look at `load-in-progress' to tell whether we're called
-      ;; directly in the file being compiled or just from some file
-      ;; being loaded during compilation.
+  (if (not (cc-bytecomp-is-loading))
       (let (p)
         (if cc-bytecomp-environment-set
             (error "Byte compilation environment already set - \
@@ -143,7 +190,7 @@ perhaps a `cc-bytecomp-restore-environment' is forgotten somewhere"))
 (defun cc-bytecomp-restore-environment ()
   ;; Eval'ed during compilation to restore variables, functions etc
   ;; declared with `cc-bytecomp-defvar' et al.
-  (if (not load-in-progress)
+  (if (not (cc-bytecomp-is-loading))
       (let (p)
         (setq p cc-bytecomp-unbound-variables)
         (while p
@@ -287,8 +334,7 @@ use within `eval-when-compile'."
   `(eval-when-compile
      (if (and (fboundp 'cc-bytecomp-is-compiling)
               (cc-bytecomp-is-compiling))
-         (if (or (not load-in-progress)
-                 (not (featurep ,cc-part)))
+         (if (not (featurep ,cc-part))
              (cc-bytecomp-load (symbol-name ,cc-part)))
        (require ,cc-part))))
 
@@ -301,12 +347,6 @@ afterwards.  Don't use within `eval-when-compile'."
      (require ,feature)
      (eval-when-compile (cc-bytecomp-setup-environment))))
 
-(defun cc-bytecomp-is-compiling ()
-  "Return non-nil if eval'ed during compilation.  Don't use outside
-`eval-when-compile'."
-  (and (boundp 'byte-compile-dest-file)
-       (stringp byte-compile-dest-file)))
-
 (defmacro cc-bytecomp-defvar (var)
   "Binds the symbol as a variable during compilation of the file,
 to silence the byte compiler.  Don't use within `eval-when-compile'."
@@ -320,8 +360,7 @@ to silence the byte compiler.  Don't use within `eval-when-compile'."
               "cc-bytecomp-defvar: Saving %s (as unbound)" ',var)
              (setq cc-bytecomp-unbound-variables
                    (cons ',var cc-bytecomp-unbound-variables))))
-       (if (and (cc-bytecomp-is-compiling)
-                (not load-in-progress))
+       (if (cc-bytecomp-is-compiling)
            (progn
              (defvar ,var)
              (set ',var (intern (concat "cc-bytecomp-ignore-var:"
@@ -349,8 +388,7 @@ at compile time, e.g. for macros and inline functions."
              (setq cc-bytecomp-original-functions
                    (cons (list ',fun nil 'unbound)
                          cc-bytecomp-original-functions))))
-       (if (and (cc-bytecomp-is-compiling)
-                (not load-in-progress))
+       (if (cc-bytecomp-is-compiling)
            (progn
              (fset ',fun (intern (concat "cc-bytecomp-ignore-fun:"
                                          (symbol-name ',fun))))
diff --git a/lisp/progmodes/cc-defs.el b/lisp/progmodes/cc-defs.el
index 2ea566a7a25..d0beab1d485 100644
--- a/lisp/progmodes/cc-defs.el
+++ b/lisp/progmodes/cc-defs.el
@@ -1983,19 +1983,22 @@ system."
 
 (defvar c-lang-const-expansion nil)
 
+;; Ugly hack to pull in the definition of `cc-bytecomp-compiling-or-loading`
+;; from cc-bytecomp to make it available at loadtime.  This is the same
+;; mechanism used in cc-mode.el for `c-populate-syntax-table'.
+(defalias 'cc-bytecomp-compiling-or-loading
+  (cc-eval-when-compile
+    (let ((f (symbol-function 'cc-bytecomp-compiling-or-loading)))
+      (if (byte-code-function-p f) f (byte-compile f)))))
+
 (defsubst c-get-current-file ()
   ;; Return the base name of the current file.
-  (let ((file (cond
-               (load-in-progress
-                ;; Being loaded.
-                load-file-name)
-               ((and (boundp 'byte-compile-dest-file)
-                     (stringp byte-compile-dest-file))
-                ;; Being compiled.
-                byte-compile-dest-file)
-               (t
-                ;; Being evaluated interactively.
-                (buffer-file-name)))))
+  (let* ((c-or-l (cc-bytecomp-compiling-or-loading))
+         (file
+          (cond
+           ((eq c-or-l 'loading) load-file-name)
+           ((eq c-or-l 'compiling) byte-compile-dest-file)
+           ((null c-or-l) (buffer-file-name)))))
     (and file
          (file-name-sans-extension
           (file-name-nondirectory file)))))
@@ -2062,6 +2065,9 @@ constant.  A file is identified by its base name."
          ;; language constant source definitions.)
          (c-lang-const-expansion 'call)
          (c-langs-are-parametric t)
+         (file (intern
+                (or (c-get-current-file)
+                    (error "`c-lang-defconst' can only be used in a file"))))
          bindings
          pre-files)
 
@@ -2121,9 +2127,14 @@ constant.  A file is identified by its base name."
     ;; definitions for this symbol, to make sure the order in the
     ;; `source' property is correct even when files are loaded out of
     ;; order.
-    (setq pre-files (nreverse
-                     ;; Reverse to get the right load order.
-                     (mapcar 'car (get sym 'source))))
+    (setq pre-files (mapcar 'car (get sym 'source)))
+    (if (memq file pre-files)
+        ;; This can happen when the source file (e.g. cc-langs.el) is first
+        ;; loaded as source, setting a 'source property entry, and then itself
+        ;; being compiled.
+        (setq pre-files (cdr (memq file pre-files))))
+    ;; Reverse to get the right load order.
+    (setq pre-files (nreverse pre-files))
 
     `(eval-and-compile
        (c-define-lang-constant ',name ,bindings
@@ -2233,9 +2244,7 @@ quoted."
         (if (or (eq c-lang-const-expansion 'call)
                 (and (not c-lang-const-expansion)
                      (not mode))
-                load-in-progress
-                (not (boundp 'byte-compile-dest-file))
-                (not (stringp byte-compile-dest-file)))
+                (not (cc-bytecomp-is-compiling)))
             ;; Either a straight call is requested in the context, or
             ;; we're in an "uncontrolled" context and got no language,
             ;; or we're not being byte compiled so the compile time
diff --git a/lisp/progmodes/cc-langs.el b/lisp/progmodes/cc-langs.el
index 17d717e740f..4d16a9b9d33 100644
--- a/lisp/progmodes/cc-langs.el
+++ b/lisp/progmodes/cc-langs.el
@@ -3260,10 +3260,7 @@ function it returns is byte compiled with all the evaluated results
 from the language constants.  Use the `c-init-language-vars' macro to
 accomplish that conveniently."
 
-  (if (and (not load-in-progress)
-           (boundp 'byte-compile-dest-file)
-           (stringp byte-compile-dest-file))
-
+  (if (cc-bytecomp-is-compiling)
       ;; No need to byte compile this lambda since the byte compiler is
       ;; smart enough to detect the `funcall' construct in the
       ;; `c-init-language-vars' macro below and compile it all straight