[BUG] Regexp compiler, problem with character classes

[bojohan+mail@dd.chalmers.se (Johan Bockgård)]

[I'm resending this because I think it's a serious bug. It makes
character classes totally unreliable.]

Character classes are translated to character alternatives during the
regexp compile phase. This is wrong, since the syntax table should be
taken into account during the actual matching. This may be non-trivial
to fix.


    (with-temp-buffer
      (list
       (progn (modify-syntax-entry ?a " ")
              (string-match "x[[:space:]]" "xa"))
       (progn (modify-syntax-entry ?a "w")
              (string-match "x[[:space:]]" "xa"))))
    => (0 0)



0:      /exactn/1/x
3:      /charset [\t\f a\302\200-\303\277]
37:     /succeed
38:     end of pattern.

Compiling pattern: x[[:space:]]

Compiled pattern: 
38 bytes used/174 bytes allocated.
fastmap: x
re_nsub: 0      regs_alloc: 0   can_be_null: 0  no_sub: 0       not_bol: 0      not_eol: 0      syntax: 340204
0:      /exactn/1/x
3:      /charset [\t\f a\302\200-\303\277]
37:     /succeed
38:     end of pattern.
0:      /exactn/1/x
3:      /charset [\t\f a\302\200-\303\277]
37:     /succeed
38:     end of pattern.



As an effect you get the behavior below, since the compiler takes no
care to setup the syntax in the first place:


1)

    emacs -Q

    (with-temp-buffer
      (string-match "x[[:space:]]" "x\n"))

    => nil

(exit Emacs)


2)
    emacs -Q

    (with-temp-buffer
      (char-syntax ?\n)
      (string-match "x[[:space:]]" "x\n"))

    => 0


(Fchar_syntax does
    gl_state.current_syntax_table = current_buffer->syntax_table;)

-- 
This is bad.