Re: [PATCH v4 0/3] Split logging functionality out of EAL

[Bruce Richardson <bruce.richardson@intel.com>]

On Sun, Jan 22, 2023 at 03:56:12PM +0100, David Marchand wrote:
> Hi Bruce,
> 
> On Fri, Jan 20, 2023 at 7:22 PM Bruce Richardson
> <bruce.richardson@intel.com> wrote:
> >
> > There is a general desire to reduce the size and scope of EAL. To this
> > end, this patchset makes a (very) small step in that direction by taking
> > the logging functionality out of EAL and putting it into its own library
> > that can be built and maintained separately.
> >
> > As with the first RFC for this, the main obstacle is the "fnmatch"
> > function which is needed by both EAL and the new log function when
> > building on windows. While the function cannot stay in EAL - or we would
> > have a circular dependency, moving it to a new library or just putting
> > it in the log library have the disadvantages that it then "leaks" into
> > the public namespace without an rte_prefix, which could cause issues.
> > Since only a single function is involved, subsequent versions take a
> > different approach to v1, and just moves the offending function to be a
> > static function in a header file. This allows use by multiple libs
> > without conflicting names or making it public.
> >
> > The other complication, as explained in v1 RFC was that of multiple
> > implementations for different OS's. This is solved here in the same
> > way as v1, by including the OS in the name and having meson pick the
> > correct file for each build. Since only one file is involved, there
> > seemed little need for replicating EAL's separate subdirectories
> > per-OS.
> 
> There is another complication.
> 
> The ABI check is not handling properly the case where symbols are
> moved to the new log library (even though the dependency to librte_log
> is explicit in librte_eal elf).
> For now, I don't have a good way to handle this.
> 
> A workaround to pass the check is to suppress those symbols wrt the eal dump:
> [suppress_function]
>         symbol_name_regexp = rte_log
> [suppress_function]
>         symbol_name = rte_openlog_stream
> [suppress_function]
>         symbol_name = rte_vlog
> 
> But this is not a good solution because we would be losing checks on
> them for the rest of the v23 ABI life.
> 
Right, I got error messages from the CI job for this too, but I also have
no idea how to work around this. Perhaps we only get to move content
between libraries when we do an ABI bump? Seems a bit restrictive, though.

/Bruce