bfstd: Fix an OOB string index in xmbrtowc()

This bug could be reproduced with something like

    $ bfs -samefile $'\xFA\xFA'
    bfs: error: bfs: dstrnescat@src/dstring.c:252: wordesc() result truncated

or worse, with -DNDEBUG,

    $ bfs -samefile $'.....................\xFA\xFA'
    bfs: error: bfs -samefile $'.....................\xFA\xFA\x00\x55\x53\x45\x52\x3D\x74\x61\x76\x69\x61\x6E\x61\x74\x6F\x72
    bfs: error:               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    bfs: error: No such file or directory.

which prints the memory after the end of the string (in this case, the
environment variable USER=tavianator).

The bug was caused by the line `*i += len`, which was intended to be
`*i = len`.  But actually, the right behaviour seems to be `*i += 1`.

Fixes: 19c96abe0a1ee56cf206fd5e87defb1fd3e0daa5

0 files changed, 0 insertions, 0 deletions