Package: multitail
Version: 6.4.2-1
Severity: normal
Dear Maintainer,
if the locale settings are somewhat utf-8-ish, illegal utf-8 character
sequences break any future multitail output until the program is
terminated. Instead of the actual text, the string "^`" is printed for
each character, inverted.
Reproducer:
printf '\xf8\xa7\nhello\n' | LANG=en_US.UTF-8 multitail -j
Analysis:
The mbsrtowcs invocation in mt.c might fail. The program does not catch
this but uses the pre-defined value for wcur which is the null byte.
The documentation states the value is undefined but appearently it's
just left untouched. That null value is considered a control character
and the code to print that generates the observed sequence (it should
rather be "^@", different story).
The surprising thing is any future invocations to mbsrtowcs will fail,
too. Appearently the internal state is distorted in a way it cannot
recover even when processing sound input. This might be an issue in
glibc, I've filed #824429
Workaround:
Set LANG to C before calling multitail.
Possible fixes:
- Set LC_CTYPE to "C" instead of "" in main. Unless this has other
side effects.
- Instead of using the internal state, provide one on our own,
and reset it upon error, see below.
In either way it's a good idea to set wcur to the question mark to
indicate a character conversion error. More elaborate things were
printing it inverted and/or using the replacement character U+FFFD for
this. Figuring out side effects is left as an exercise to the reader.
Christoph
--- a/mt.c
+++ b/mt.c
@@ -617,8 +617,12 @@ void do_color_print(proginfo *cur, char *use_string, int
prt_start, int prt_end,
#ifdef UTF8_SUPPORT
const char *dummy = &use_string[offset];
- wchar_t wcur = 0;
- mbsrtowcs(&wcur, &dummy, 1, NULL);
+ wchar_t wcur;
+ static mbstate_t state;
+ if (mbsrtowcs(&wcur, &dummy, 1, &state) == -1) {
+ wcur = '?';
+ memset (&state, '\0', sizeof (mbstate_t));
+ }
#else
char wcur = use_string[offset];
#endif
-- System Information:
Debian Release: stretch/sid
APT prefers testing
APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Kernel: Linux 4.4.9 (SMP w/4 CPU cores)
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
Shell: /bin/sh linked to /bin/dash
Init: unable to detect
Versions of packages multitail depends on:
ii libc6 2.22-7
ii libncursesw5 6.0+20160319-1
ii libtinfo5 6.0+20160319-1
multitail recommends no packages.
multitail suggests no packages.
-- no debconf information
