Graph fails for labels ending backslash-space

[human]

Hello,

rrdgraph refuses to draw a graph that has a label ending in backslash-space. Zero or two spaces are OK. Double-escaping doesn't help.

Reproducer:

#!/bin/sh

RRD=backslash-space.rrd

BIN=rrdtool

T0=$(date +%s)

$BIN create $RRD \
    --start $(($T0-3600)) \
    --step=300 \
    DS:42:GAUGE:600:U:U \
    RRA:AVERAGE:0.5:1:12

$BIN update $RRD "$T0:1"

# only relevant difference is in LINE1

$BIN graph backslash-space.1.png \
    "DEF:glabel=$RRD:42:AVERAGE" \
    'LINE1:glabel#330099:usage \\' \
    "GPRINT:glabel:LAST:%6.2lf%s" \
    --start $(($T0 - 3600))  --end $T0

$BIN graph backslash-space.2.png \
    "DEF:glabel=$RRD:42:AVERAGE" \
    'LINE1:glabel#330099:usage \\ ' \
    "GPRINT:glabel:LAST:%6.2lf%s" \
    --start $(($T0 - 3600))  --end $T0

Expected: 481x155 (two times)

Got: Just one time, then

ERROR: Unknown control code at the end of ' usage XX '

(where XX is two backslashes, trac prefers to eat them)

This wasn't so bad if munin wouldn't attach a space to a label for padding. In other words, every plugin that has a field label ending in a backslash will not be drawn in munin.

Found in 1.4.3 (Debian squeeze) and 1.4.6 (compiled from source).

Regards,

Christoph

[oetiker]

The reason for this error is, that rrdtool now makes sure that only valid backslash escapes are used to terminate a string. There is curently no way of producing a string ending in backlash and a single character. You could have two spaces at end of the string.

In r2262 I added a \. control which acts as a nop ... so you can now do

COMMENT:\ \.

cheers tobi

[human]

Sorry, but that is not an acceptable solution. Doing this puts load onto the users of rrdgraph in a rather unusual way. Looking around in in the sources at leg_place I strongly suggest to re-write the escape character handling into a parsing from left to right. This would also allow literal '\t' sequences somewhere in the middle of a label, something not possible at the moment as in:

$BIN graph backslash-space.1.png \
    "DEF:glabel=$RRD:42:AVERAGE" \
    'LINE1:glabel#330099:usage C\:\\tmp' \
    "GPRINT:glabel:LAST:%6.2lf%s" \
    --start $(($T0 - 3600))  --end $T0

[oetiker]

isn't it cool with opensource that you can get right to it, rectifying the unacceptable by writing an appropriate patch, supporting escape sequences throughout the string ... I agree, this would be a nice feature, note though that until now, backslashes inside the string had no special significance and were printed as-is ... so you would have to add some means to enable the new behavior, as it would probably break some existing uses.