[PATCH, doc RFA] PR guile/17177: replace *pretty-printers*

[Doug Evans <dje at google dot com>]

Hi.
This patch implements the fix for pr 17177.
Namely it replaces Guile global *pretty-printers*
with two functions: pretty-printers, set-pretty-printers!.

2014-07-19  Doug Evans  <xdje42@gmail.com>

	PR guile/17177
	* guile/lib/gdb.scm (pretty-printers): Export.
	(set-pretty-printers!): Export.
	* guile/lib/gdb/printing.scm (gdb module): Update.
	(prepend-pretty-printer!, append-pretty-printer!): Update.
	* guile/scm-pretty-print.c (pretty_printer_list_name): Delete.
	(pretty_printer_list_var): Delete.
	(pretty_printer_list): New static global.
	(gdbscm_pretty_printers): New function.
	(gdbscm_set_pretty_printers_x): New function.
	(ppscm_find_pretty_printer_from_gdb): Update.
	(pretty_printer_functions): Add pretty-printers, set-pretty-printers!.
	(gdbscm_initialize_pretty_printers): Update.

	doc/
	* guile.texi (Guile Pretty Printing API): Fix typo.
	Document set-pretty-printers!, pretty-printers.
	(Selecting Guile Pretty-Printers): Update.
	Mention program-space based pretty-printers.

diff --git a/gdb/doc/guile.texi b/gdb/doc/guile.texi
index 4aaba8a..a6ce2da 100644
--- a/gdb/doc/guile.texi
+++ b/gdb/doc/guile.texi
@@ -1377,7 +1377,16 @@ Otherwise return @code{#f}.
 
 @deffn {Scheme Procedure} set-pretty-printer-enabled! pretty-printer flag
 Set the enabled flag of @var{pretty-printer} to @var{flag}.
-The value returned in unspecified.
+The value returned is unspecified.
+@end deffn
+
+@deffn {Scheme Procedure} pretty-printers
+Return the list of global pretty-printers.
+@end deffn
+
+@deffn {Scheme Procedure} set-pretty-printers! pretty-printers
+Set the list of global pretty-printers to @var{pretty-printers}.
+The value returned is unspecified.
 @end deffn
 
 @deffn {Scheme Procedure} make-pretty-printer-worker display-hint to-string children
@@ -1476,27 +1485,36 @@ printer exists, then this returns @code{#f}.
 @subsubsection Selecting Guile Pretty-Printers
 @cindex selecting guile pretty-printers
 
-The Guile list @code{*pretty-printers*} contains a set of
-@code{<gdb:pretty-printer>} registered objects.
-Printers in this list are called @code{global}
-printers, they're available when debugging any inferior.
-In addition to this, each @code{<gdb:objfile>} object contains its
-own set of pretty-printers (@pxref{Objfiles In Guile}).
+There are three sets of pretty-printers that @value{GDBN} searches:
+
+@itemize @bullet
+@item
+Per-objfile list of pretty-printers (@pxref{Objfiles In Guile}).
+@item
+Per-progspace list of pretty-printers (@pxref{Progspaces In Guile}).
+@item
+The global list of pretty-printers (@pxref{Guile Pretty Printing API}).
+These printers are available when debugging any inferior.
+@end itemize
 
 Pretty-printer lookup is done by passing the value to be printed to the
 lookup function of each enabled object in turn.
 Lookup stops when a lookup function returns a non-@code{#f} value
 or when the list is exhausted.
+Lookup functions must return either a @code{<gdb:pretty-printer-worker>}
+object or @code{#f}.  Otherwise an exception is thrown.
 
 @value{GDBN} first checks the result of @code{objfile-pretty-printers}
 of each @code{<gdb:objfile>} in the current program space and iteratively
 calls each enabled lookup function in the list for that @code{<gdb:objfile>}
 until a non-@code{#f} object is returned.
-Lookup functions must return either a @code{<gdb:pretty-printer-worker>}
-object or @code{#f}.  Otherwise an exception is thrown.
 If no pretty-printer is found in the objfile lists, @value{GDBN} then
-searches the global pretty-printer list, calling each enabled function
-until a non-@code{#f} object is returned.
+searches the result of @code{progspace-pretty-printers} of the current
+program space, calling each enabled function until a non-@code{#f} object
+is returned.
+After these lists have been exhausted, it tries the global pretty-printers
+list, obtained with @code{pretty-printers}, again calling each enabled
+function until a non-@code{#f} object is returned.
 
 The order in which the objfiles are searched is not specified.  For a
 given list, functions are always invoked from the head of the list,
diff --git a/gdb/guile/lib/gdb.scm b/gdb/guile/lib/gdb.scm
index 120fcc6..4fd4699 100644
--- a/gdb/guile/lib/gdb.scm
+++ b/gdb/guile/lib/gdb.scm
@@ -319,6 +319,8 @@
  set-pretty-printer-enabled!
  make-pretty-printer-worker
  pretty-printer-worker?
+ pretty-printers
+ set-pretty-printers!
 
  ;; scm-progspace.c
 
diff --git a/gdb/guile/lib/gdb/printing.scm b/gdb/guile/lib/gdb/printing.scm
index eac9417..2d1274f 100644
--- a/gdb/guile/lib/gdb/printing.scm
+++ b/gdb/guile/lib/gdb/printing.scm
@@ -19,7 +19,8 @@
 
 (define-module (gdb printing)
   #:use-module ((gdb) #:select
-		(*pretty-printers* pretty-printer? objfile? progspace?
+		(pretty-printer? objfile? progspace?
+		 pretty-printers set-pretty-printers!
 		 objfile-pretty-printers set-objfile-pretty-printers!
 		 progspace-pretty-printers set-progspace-pretty-printers!))
   #:use-module (gdb init))
@@ -30,7 +31,7 @@ If OBJ is #f, add MATCHER to the global list."
   (%assert-type (pretty-printer? matcher) matcher SCM_ARG1
 		'prepend-pretty-printer!)
   (cond ((eq? obj #f)
-	 (set! *pretty-printers* (cons matcher *pretty-printers*)))
+	 (set-pretty-printers! (cons matcher (pretty-printers))))
 	((objfile? obj)
 	 (set-objfile-pretty-printers!
 	  obj (cons matcher (objfile-pretty-printers obj))))
@@ -46,7 +47,7 @@ If OBJ is #f, add MATCHER to the global list."
   (%assert-type (pretty-printer? matcher) matcher SCM_ARG1
 		'append-pretty-printer!)
   (cond ((eq? obj #f)
-	 (set! *pretty-printers* (append! *pretty-printers* (list matcher))))
+	 (set-pretty-printers! (append! (pretty-printers) (list matcher))))
 	((objfile? obj)
 	 (set-objfile-pretty-printers!
 	  obj (append! (objfile-pretty-printers obj) (list matcher))))
diff --git a/gdb/guile/scm-pretty-print.c b/gdb/guile/scm-pretty-print.c
index e20da68..79b9e64 100644
--- a/gdb/guile/scm-pretty-print.c
+++ b/gdb/guile/scm-pretty-print.c
@@ -111,11 +111,8 @@ static const char pretty_printer_worker_smob_name[] =
 static scm_t_bits pretty_printer_smob_tag;
 static scm_t_bits pretty_printer_worker_smob_tag;
 
-/* Global list of pretty-printers.  */
-static const char pretty_printer_list_name[] = "*pretty-printers*";
-
-/* The *pretty-printer* variable.  */
-static SCM pretty_printer_list_var;
+/* The global pretty-printer list.  */
+static SCM pretty_printer_list;
 
 /* gdb:pp-type-error.  */
 static SCM pp_type_error_symbol;
@@ -239,6 +236,29 @@ gdbscm_set_pretty_printer_enabled_x (SCM self, SCM enabled)
 
   return SCM_UNSPECIFIED;
 }
+
+/* (pretty-printers) -> list
+   Returns the list of global pretty-printers.  */
+
+static SCM
+gdbscm_pretty_printers (void)
+{
+  return pretty_printer_list;
+}
+
+/* (set-pretty-printers! list) -> unspecified
+   Set the global pretty-printers list.  */
+
+static SCM
+gdbscm_set_pretty_printers_x (SCM printers)
+{
+  SCM_ASSERT_TYPE (gdbscm_is_true (scm_list_p (printers)), printers,
+		   SCM_ARG1, FUNC_NAME, _("list"));
+
+  pretty_printer_list = printers;
+
+  return SCM_UNSPECIFIED;
+}
 
 /* Administrivia for pretty-printer-worker smobs.
    These are created when a matcher recognizes a value.  */
@@ -457,11 +477,8 @@ ppscm_find_pretty_printer_from_progspace (SCM value)
 static SCM
 ppscm_find_pretty_printer_from_gdb (SCM value)
 {
-  SCM pp_list, pp;
+  SCM pp = ppscm_search_pp_list (pretty_printer_list, value);
 
-  /* Fetch the global pretty printer list.  */
-  pp_list = scm_variable_ref (pretty_printer_list_var);
-  pp = ppscm_search_pp_list (pp_list, value);
   return pp;
 }
 
@@ -1074,6 +1091,15 @@ Create a <gdb:pretty-printer-worker> object.\n\
     "\
 Return #t if the object is a <gdb:pretty-printer-worker> object." },
 
+  { "pretty-printers", 0, 0, 0, gdbscm_pretty_printers,
+    "\
+Return the list of global pretty-printers." },
+
+  { "set-pretty-printers!", 1, 0, 0,
+    gdbscm_set_pretty_printers_x,
+    "\
+Set the list of global pretty-printers." },
+
   END_FUNCTIONS
 };
 
@@ -1094,12 +1120,7 @@ gdbscm_initialize_pretty_printers (void)
 
   gdbscm_define_functions (pretty_printer_functions, 1);
 
-  scm_c_define (pretty_printer_list_name, SCM_EOL);
-
-  pretty_printer_list_var
-    = scm_c_private_variable (gdbscm_module_name,
-			      pretty_printer_list_name);
-  gdb_assert (!gdbscm_is_false (pretty_printer_list_var));
+  pretty_printer_list = SCM_EOL;
 
   pp_type_error_symbol = scm_from_latin1_symbol ("gdb:pp-type-error");