[patch] command :helpt {dir} leaks memory when directory does not exist

[Dominique Pellé]

Hi

afl-fuzz found that command :helpt {dir} leaks memory
in Vim-7.4.909 when the directory argument does not
exist (E150). Valgrind says:

==4962== 2 bytes in 1 blocks are definitely lost in loss record 1 of 125
==4962== at 0x4C2AB80: malloc (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4962== by 0x4E27E3: lalloc (misc2.c:921)
==4962== by 0x4E26F1: alloc (misc2.c:820)
==4962== by 0x4E2BF4: vim_strsave (misc2.c:1246)
==4962== by 0x486B15: ExpandOne (ex_getln.c:3686)
==4962== by 0x460C19: ex_helptags (ex_cmds.c:6572)
==4962== by 0x46E052: do_one_cmd (ex_docmd.c:2961)
==4962== by 0x46AD47: do_cmdline (ex_docmd.c:1133)
==4962== by 0x46A383: do_cmdline_cmd (ex_docmd.c:738)
==4962== by 0x5DD77A: exe_commands (main.c:2926)
==4962== by 0x5DAD5C: main (main.c:961)

Leak can be reproduced with:

$ vim -u NONE -c 'helpt@'

Attached patch fixes it.

Regards
Dominique

[Bram Moolenaar]

Thanks!

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