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Re: [patch] fixed uninitialized memory access in i_CTRL-X_s (spell suggestion)

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  • Tony Mechelynck
    ... U+0300 is a combining grave accent, its UTF-8 representation in hex is CC 80. Maybe Vim chokes on the 0x80 trailing byte? Any byte except the first in the
    Message 1 of 5 , Aug 1, 2010
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      On 01/08/10 16:06, Bram Moolenaar wrote:
      >
      > Dominique Pelle wrote:
      >
      >> I still see other Valgrind errors with spell suggestion with
      >> Vim-7.2.446 and Vim-7.3c (2448:943280505f72) when doing:
      >>
      >> $ valgrind --num-callers=50 --track-origins=yes 2> vg.log \
      >> vim -u NONE -c 'set spell|call feedkeys("i,,\<C-X>s")'
      >>
      >> ==4200== Conditional jump or move depends on uninitialised value(s)
      >> ==4200== at 0x8123C84: utf_head_off (mbyte.c:3290)
      >> ==4200== by 0x8198E00: suggest_trie_walk (spell.c:11666)
      >> ==4200== by 0x8197E64: suggest_try_change (spell.c:11229)
      >> ==4200== by 0x8197100: spell_suggest_intern (spell.c:10777)
      >> ==4200== by 0x8196D1E: spell_find_suggest (spell.c:10641)
      >> ==4200== by 0x81966A3: spell_suggest_list (spell.c:10494)
      >> ==4200== by 0x81A248D: expand_spelling (spell.c:16021)
      >> ==4200== by 0x806AD4E: ins_compl_get_exp (edit.c:4163)
      >> ==4200== by 0x806B793: ins_compl_next (edit.c:4506)
      >> ==4200== by 0x806C9DB: ins_complete (edit.c:5139)
      >> ==4200== by 0x80669B4: edit (edit.c:1366)
      >> ==4200== by 0x8134208: invoke_edit (normal.c:9024)
      >> ==4200== by 0x81341AE: nv_edit (normal.c:8997)
      >> ==4200== by 0x8127B87: normal_cmd (normal.c:1190)
      >> ==4200== by 0x80E8E97: main_loop (main.c:1260)
      >> ==4200== by 0x80E88CC: main (main.c:965)
      >> ==4200== Uninitialised value was created by a stack allocation
      >> ==4200== at 0x8197D56: suggest_try_change (spell.c:11204)
      >>
      >> Attached new patch fixes it but don't think it's ideal
      >> since giving spell suggestion when only typing punctuation
      >> does not make much sense.
      >
      > Thanks. I'll include it as is.
      >
      > While trying to reproduce this I encountered a crash: Soundfolding
      > breaks on a 0x300 character.
      >
      > Perhaps there are a few more bugs in this area...
      >

      U+0300 is a combining grave accent, its UTF-8 representation in hex is
      CC 80. Maybe Vim chokes on the 0x80 trailing byte? Any byte except the
      first in the UTF-8 representation of a Unicode codepoint may have that
      value without being in any way "special".

      As a reminder, UTF-8 strictly segregates the values bytes may have, as
      follows:

      00-7F single bytes
      80-BF trailing bytes (any but the first) in a multibyte sequence
      C0-DF first byte in a 2-byte sequence
      E0-EF first byte in a 3-byte sequence
      F0-F7 first byte in a 4-byte sequence
      F8-FB first byte in a 5-byte sequence
      FC-FD first byte in a 6-byte sequence
      FE-FF invalid

      In addition, the Unicode Consortium has decided that no codepoint will
      ever be accepted above U+10FFFD, not even for private use, and that
      "overlong sequences" are not to be tolerated; this makes byte values F5
      and above "invalid for interchange".


      Best regards,
      Tony.
      --
      Economics, n.:
      Economics is the study of the value and meaning of J. K.
      Galbraith ...
      -- Mike Harding, "The Armchair Anarchist's Almanac"

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