rtla: Fix parsing of multi-character short options

A bug was reported where the parsing of multi-character short options,
be it a short option with an argument specified without space (e.g.
"-p100") or multiple short options in one argument (e.g. -un), ignores
options specific to individual tools.

Furthermore, if the rest of the option is supposed to be an argument, it
gets reinterpreted as a string of options. For example, -p100 gets
interpreted as -100, which is due to hackish implementation read as
--no-thread --no-irq --no-irq with timerlat hist, causing rtla to error
out:

$ rtla timerlat hist -p100
no-irq and no-thread set, there is nothing to do here

This behavior is caused by getopt_long() being called twice on each
argument, once in common_parse_options(), once in [tool]_parse_args():

- common_parse_options() calls getopt_long() with an array of options
  common for all rtla tools, while suppressing errors (opterr = 0).
- If the option fails to parse, common_parse_options() returns 0.
- If 0 is returned from common_parse_options(), [tool]_parse_args()
  calls getopt_long() again, with its own set of options.

* [tool] means one of {osnoise,timerlat}_{top,hist}

At least in glibc, getopt_long() increments its internal nextchar
variable even if the option is not recognized. That means that in the
case of "-p100", common_parse_options() sets nextchar pointing to '1',
and timerlat_hist_parse_args() sees '1', not 'p'; the same then repeats
for the first and second '0'.

As there is no way to restore the correct internal state of
getopt_long() reliably, fix the issue by merging the common options back
to the longopt array and option string of the [tool]_parse_args()
functions using a macro; only the switch part is left in the original
function, which is renamed to set_common_option().

Fixes: 850cd24cb6d6 ("tools/rtla: Add common_parse_options()")
Reported-by: John Kacur <jkacur@redhat.com>
Tested-by: John Kacur <jkacur@redhat.com>
Link: https://lore.kernel.org/r/20260602125506.3325345-1-tglozar@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>

0 files changed, 0 insertions, 0 deletions