view etc/ETAGS.EBNF @ 5146:88bd4f3ef8e4

make lrecord UID's have a separate UID space for each object, resurrect debug SOE code in extents.c -------------------- ChangeLog entries follow: -------------------- src/ChangeLog addition: 2010-03-15 Ben Wing <ben@xemacs.org> * alloc.c: * alloc.c (c_readonly): * alloc.c (deadbeef_memory): * alloc.c (make_compiled_function): * alloc.c (make_button_data): * alloc.c (make_motion_data): * alloc.c (make_process_data): * alloc.c (make_timeout_data): * alloc.c (make_magic_data): * alloc.c (make_magic_eval_data): * alloc.c (make_eval_data): * alloc.c (make_misc_user_data): * alloc.c (noseeum_make_marker): * alloc.c (ADDITIONAL_FREE_string): * alloc.c (common_init_alloc_early): * alloc.c (init_alloc_once_early): * bytecode.c (print_compiled_function): * bytecode.c (mark_compiled_function): * casetab.c: * casetab.c (print_case_table): * console.c: * console.c (print_console): * database.c (print_database): * database.c (finalize_database): * device-msw.c (sync_printer_with_devmode): * device-msw.c (print_devmode): * device-msw.c (finalize_devmode): * device.c: * device.c (print_device): * elhash.c: * elhash.c (print_hash_table): * eval.c (print_multiple_value): * eval.c (mark_multiple_value): * events.c (deinitialize_event): * events.c (print_event): * events.c (event_equal): * extents.c: * extents.c (soe_dump): * extents.c (soe_insert): * extents.c (soe_delete): * extents.c (soe_move): * extents.c (extent_fragment_update): * extents.c (print_extent_1): * extents.c (print_extent): * extents.c (vars_of_extents): * frame.c: * frame.c (print_frame): * free-hook.c: * free-hook.c (check_free): * glyphs.c: * glyphs.c (print_image_instance): * glyphs.c (print_glyph): * gui.c: * gui.c (copy_gui_item): * hash.c: * hash.c (NULL_ENTRY): * hash.c (KEYS_DIFFER_P): * keymap.c (print_keymap): * keymap.c (MARKED_SLOT): * lisp.h: * lrecord.h: * lrecord.h (LISP_OBJECT_UID): * lrecord.h (set_lheader_implementation): * lrecord.h (struct old_lcrecord_header): * lstream.c (print_lstream): * lstream.c (finalize_lstream): * marker.c (print_marker): * marker.c (marker_equal): * mc-alloc.c (visit_all_used_page_headers): * mule-charset.c: * mule-charset.c (print_charset): * objects.c (print_color_instance): * objects.c (print_font_instance): * objects.c (finalize_font_instance): * opaque.c (print_opaque): * opaque.c (print_opaque_ptr): * opaque.c (equal_opaque_ptr): * print.c (internal_object_printer): * print.c (enum printing_badness): * rangetab.c (print_range_table): * rangetab.c (range_table_equal): * specifier.c (print_specifier): * specifier.c (finalize_specifier): * symbols.c: * symbols.c (print_symbol_value_magic): * tooltalk.c: * tooltalk.c (print_tooltalk_message): * tooltalk.c (print_tooltalk_pattern): * window.c (print_window): * window.c (debug_print_window): (1) Make lrecord UID's have a separate UID space for each object. Otherwise, with 20-bit UID's, we rapidly wrap around, especially when common objects like conses and strings increment the UID value for every object created. (Originally I tried making two UID spaces, one for objects that always print readably and hence don't display the UID, and one for other objects. But certain objects like markers for which a UID is displayed are still generated rapidly enough that UID overflow is a serious issue.) This also has the advantage of making UID values smaller, hence easier to remember -- their main purpose is to make it easier to keep track of different objects of the same type when debugging code. Make sure we dump lrecord UID's so that we don't have problems with pdumped and non-dumped objects having the same UID. (2) Display UID's consistently whenever an object (a) doesn't consistently print readably (objects like cons and string, which always print readably, can't display a UID), and (b) doesn't otherwise have a unique property that makes objects of a particular type distinguishable. (E.g. buffers didn't and still don't print an ID, but the buffer name uniquely identifies the buffer.) Some types, such as event, extent, compiled-function, didn't always (or didn't ever) display an ID; others (such as marker, extent, lstream, opaque, opaque-ptr, any object using internal_object_printer()) used to display the actual machine pointer instead. (3) Rename NORMAL_LISP_OBJECT_UID to LISP_OBJECT_UID; make it work over all Lisp objects and take a Lisp object, not a struct pointer. (4) Some misc cleanups in alloc.c, elhash.c. (5) Change code in events.c that "deinitializes" an event so that it doesn't increment the event UID counter in the process. Also use deadbeef_memory() to overwrite memory instead of doing the same with custom code. In the process, make deadbeef_memory() in alloc.c always available, and delete extraneous copy in mc-alloc.c. Also capitalize all uses of 0xDEADBEEF. Similarly in elhash.c call deadbeef_memory(). (6) Resurrect "debug SOE" code in extents.c. Make it conditional on DEBUG_XEMACS and on a `debug-soe' variable, rather than on SOE_DEBUG. Make it output to stderr, not stdout. (7) Delete some custom print methods that were identical to external_object_printer().
author Ben Wing <ben@xemacs.org>
date Mon, 15 Mar 2010 16:35:38 -0500
parents a827a51c3241
children 308d34e9f07d
line wrap: on
line source

-*- indented-text -*-

See the end of this file for copyright information.

This file contains two sections:

1) An EBNF (Extended Backus-Naur Form) description of the format of
    the tags file created by etags.c and interpreted by etags.el;
2) A discussion of tag names and implicit tag names.

====================== 1) EBNF tag file description =====================

Productions created from current behaviour to aid extensions
Francesco Potorti` <pot@gnu.org> 2002
----------------

FF ::= #x0c				   /* tag section starter */

LF ::= #x0a				   /* line terminator */

DEL ::= #x7f				   /* pattern terminator */

SOH ::= #x01				   /* name terminator */

regchar ::= [^#x0a#x0c#x7f]		   /* regular character */

regstring ::= { regchar }		   /* regular string */

unsint ::= [0-9] { [0-9] }		   /* non-negative integer */



tagfile ::= { tagsection }		   /* a tags file */

tagsection ::= FF LF ( includesec | regularsec ) LF

includesec ::= filename ",include" [ LF fileprop ]

regularsec ::= filename "," [ unsint ] [ LF fileprop ] { LF tag }

filename ::= regchar regstring		   /* a file name */

fileprop ::= "(" regstring ")"		   /* an elisp alist */

tag ::= directtag | patterntag

directtag ::= DEL realposition		   /* no pattern */

patterntag ::= pattern DEL [ tagname SOH ] position

pattern ::= regstring			   /* a tag pattern */

tagname ::= regchar regstring		   /* a tag name */

position ::= realposition | "," 	   /* charpos,linepos */

realposition ::= "," unsint | unsint "," | unsint "," unsint

==================== end of EBNF tag file description ====================



======================= 2) discussion of tag names =======================

- WHAT ARE TAG NAMES
Tag lines in a tags file are usually made from the above defined pattern
and by an optional tag name.  The pattern is a string that is searched
in the source file to find the tagged line.

- WHY TAG NAMES ARE GOOD
When a user looks for a tag, Emacs first compares the tag with the tag
names contained in the tags file.  If no match is found, Emacs compares
the tag with the patterns.  The tag name is then the preferred way to
look for tags in the tags file, because when the tag name is present
Emacs can find a tag faster and more accurately.  These tag names are
part of tag lines in the tags file, so we call them "explicit".

- WHY IMPLICIT TAG NAMES ARE EVEN BETTER
When a tag line has no name, but a name can be deduced from the pattern,
we say that the tag line has an implicit tag name.  Often tag names are
redundant; this happens when the name of a tag is an easily guessable
substring of the tag pattern.  We define a set of rules to decide
whether it is possible to deduce the tag name from the pattern, and make
an unnamed tag in those cases.  The name deduced from the pattern of an
unnamed tag is the implicit name of that tag.
  When the user looks for a tag, and Emacs finds no explicit tag names
that match it, Emacs then looks for an tag whose implicit tag name
matches the request.  etags.c uses implicit tag names when possible, in
order to reduce the size of the tags file.
  An implicit tag name is deduced from the pattern by discarding the
last character if it is one of ` \f\t\n\r()=,;', then taking all the
rightmost consecutive characters in the pattern which are not one of
those.

===================== end of discussion of tag names =====================

Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007
Free Software Foundation, Inc.

COPYING PERMISSIONS:

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    but WITHOUT ANY WARRANTY; without even the implied warranty of
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    GNU General Public License for more details.

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