*** empty log message ***

etc/NEWS

@@ -1087,7 +1087,7 @@ what BODY returns.
 
 +++
 ** Regular expressions now support intervals \{n,m\} as well as
-Perl's non-greedy *? +? and ?? operators.
+Perl's shy-groups \(?:...\) and non-greedy *? +? and ?? operators.
 
 +++
 ** The optional argument BUFFER of function file-local-copy has been

man/search.texi

@@ -432,16 +432,16 @@ are non-greedy variants of the operators above.  The normal operators
 as they can, while if you append a @samp{?} after them, it makes them
 non-greedy: they will match as little as possible.
 
-@item \@{n,m\@}
+@item \@{@var{n},@var{m}\@}
 is another postfix operator that specifies an interval of iteration:
-the preceding regular expression must match between @samp{n} and
-@samp{m} times.  If @samp{m} is omitted, then there is no upper bound
-and if @samp{,m} is omitted, then the regular expression must match
-exactly @samp{n} times.				@*
+the preceding regular expression must match between @var{n} and
+@var{m} times.  If @var{m} is omitted, then there is no upper bound
+and if @var{,m} is omitted, then the regular expression must match
+exactly @var{n} times.				@*
 @samp{\@{0,1\@}} is equivalent to @samp{?}.	@*
 @samp{\@{0,\@}} is equivalent to @samp{*}.	@*
 @samp{\@{1,\@}} is equivalent to @samp{+}.	@*
-@samp{\@{n\@}} is equivalent to @samp{\@{n,n\@}}.
+@samp{\@{@var{n}\@}} is equivalent to @samp{\@{@var{n},@var{n}\@}}.
 
 @item [ @dots{} ]
 is a @dfn{character set}, which begins with @samp{[} and is terminated
@@ -560,7 +560,15 @@ To record a matched substring for future reference.
 This last application is not a consequence of the idea of a
 parenthetical grouping; it is a separate feature that is assigned as a
 second meaning to the same @samp{\( @dots{} \)} construct.  In practice
-there is no conflict between the two meanings.
+there is almost no conflict between the two meanings.
+
+@item \(?: @dots{} \)
+is another grouping construct (often called ``shy'') that serves the same
+first two purposes, but not the third:
+it cannot be referred to later on by number.  This is only useful
+for mechanically constructed regular expressions where grouping
+constructs need to be introduced implicitly and hence risk changing the
+numbering of subsequent groups.
 
 @item \@var{d}
 matches the same text that matched the @var{d}th occurrence of a

src/ChangeLog

@@ -1,3 +1,85 @@
+2000-03-08  Stefan Monnier  <monnier@cs.yale.edu>
+
+	This is a big redesign of failure-stack and register handling, prompted
+	by bugs revealed when trying to add shy-groups.  Overall, what happened
+	is that loops are now structured a little differently, groups can be
+	shy and the code is a little simpler.
+
+	* regex.h: Update the copyright.
+	(RE_SHY_GROUPS): New value.
+	(RE_UNMATCHED_RIGHT_PAREN_ORD): Renumber.
+	(RE_SYNTAX_EMACS): Add RE_SHY_GROUPS.
+
+	* regex.c (enum re_opcode_t): Remove jump_past_alt, maybe_pop_jump,
+	push_dummy_failure and dumy_failure_jump.
+	Add on_failure_jump_(exclusive, loop and smart).
+	Also fix the comment for (start|stop)_memory since they now only take
+	one argument (the second has becomes unnecessary).
+	(print_partial_compiled_pattern): Adjust for changes in re_opcode_t.
+	(print_compiled_pattern): Use %ld to printf long ints and flush to make
+	debugging a little easier.
+	(union fail_stack_elt): Make the integer unsigned.
+	(struct fail_stack_type): Add a `frame' element.
+	(INIT_FAIL_STACK): Init `frame' as well.
+	(POP_PATTERN_OP): New macro for re_compile_fastmap.
+	(DEBUG_PUSH, DEBUG_POP): Remove.
+	(NUM_REG_ITEMS): Remove.
+	(NUM_NONREG_ITEMS): Adjust.
+	(FAILURE_PAT, FAILURE_STR, NEXT_FAILURE_HANDLE, TOP_FAILURE_HANDLE):
+	New macros for the cycle detection.
+	(ENSURE_FAIL_STACK): New macro for PUSH_FAILURE_(REG|POINT).
+	(PUSH_FAILURE_REG, POP_FAILURE_REG, CHECK_INFINITE_LOOP): New macros.
+	(PUSH_FAILURE_POINT): Don't push registers any more.
+	The pattern address pushed is not the destination of the jump
+	but the source of it instead.
+	(NUM_FAILURE_ITEMS): Remove.
+	(POP_FAILURE_POINT): Adapt to the new stack structure (i.e. pop
+	registers before the actual failure point).
+	Don't hardcode any meaning for str==NULL anymore.
+	(union register_info_type, REG_MATCH_NULL_STRING_P, IS_ACTIVE)
+	(MATCHED_SOMETHING, EVER_MATCHED_SOMETHING, SET_REGS_MATCHED): Remove.
+	(REG_UNSET_VALUE): Use NULL (why not?).
+	(compile_range): Remove declaration since it doesn't exist.
+	(struct compile_stack_elt_t): Remove inner_group_offset.
+	(old_reg(start|end), reg_info, reg_dummy, reg_info_dummy): Remove.
+	(regex_grow_registers): Remove dead code.
+	(FIXUP_ALT_JUMP): New macro.
+	(regex_compile): Add shy-groups
+	Change loops to use	on_failure_jump_smart&jump instead of
+	on_failure_jump&maybe_pop_jump.
+	Change + loops to eliminate the initial (dummy_failure_)jump.
+	Remove c1_base (looks like unused variable to me).
+	Use `jump' instead of `jump_past_alt' and don't bother with
+	push_dummy_failure in alternatives since it is now unnecessary.
+	Use FIXUP_ALT_JUMP.
+	Eliminate a useless `#ifdef emacs' for (re)allocating the stack.
+	(re_compile_fastmap): Remove dead variables i and num_regs.
+	Exit from loop when bufp->can_be_null rather than jumping to `done'.
+	Avoid jumping backwards so as to ensure termination.
+	Use PATTERN_STACK_EMPTY and POP_PATTERN_OP.
+	Improved handling of backreferences.
+	Remove dead code in handling of `anychar'.
+	(skip_noops, mutually_exclusive_p): New functions taken from the
+	handling of `maybe_pop_jump' in re_match_2_internal.
+	Slightly improve mutually_exclusive_p to handle ".+\n".
+	((lowest|highest)_active_reg, NO_(LOWEST|HIGHEST)_ACTIVE_REG)
+	Remove.
+	(re_match_2_internal): Use %p instead of 0x%x when printf'ing ptrs.
+	Don't SET_REGS_MATCHED anymore.  Remove many dead variables.
+	Push register (in `start_memory') on the stack rather than storing it
+	in old_reg(start|end).
+	Remove the cycle detection from `stop_memory', replaced by the use
+	of on_failure_jump_loop for greedy loops.
+	Add code for the new on_failure_jump_<foo>.
+	Remove ad-hoc code in `on_failure_jump' to push more registers
+	in the case of a loop.
+	Take out code from `maybe_pop_jump' into separate functions and
+	adapt it to the semantics of `on_failure_jump_smart'.
+	Remove jump_past_alt, dummy_failure_jump and push_dummy_failure.
+	Remove dummy_failure handling and handling of `failures to jump
+	to on_failure_jump' (this last one was already dead code, it seems).
+	((group|alt|common_op)_match_null_string_p): Remove.
+
 2000-03-08  Dave Love  <fx@gnu.org>
 
 	* config.in: Don't depend on __STDC__ for volatile.