[vbox-dev] Logging question

Michael Thayer michael.thayer at oracle.com
Fri Feb 18 14:27:06 PST 2011

Hello Jos,

Le vendredi 18 février 2011 à 12:36 -0800, Jos Backus a écrit :
> How do I write to the log file? I would expect LogAlways to always write to
> the log, but it doesn't seem to work.
One of the Log macros.  E.g. Log() for "standard" debug logging, Log2()
for second-level debug logging, LogRel() for "standard" release logging.
Standard release logging always hits the release log, regardless of log
settings.  Other logging types appear in the release or debug logs
depending on the groups and types of logging enabled.  E.g.

    export VBOX_LOG=+shared_folders.e.l.l3.f

causes standard (.e == enable), level 2 (l), level 3 (l3) and flow (f)
logging (both debug and release logging) for the shared_folders log
group to hit the debug log file.  Other types of logging will silently
be dropped.

    export VBOX_LOG_RELEASE=+shared_folders.e.l.l3.f

does the same for the release log file, but only release logging (using
the LogRel* macros) will go in.

> For example, I want to insert some logging into the following files:
> HostServices/SharedFolders/service.cpp
> HostServices/SharedFolders/vbsf.cpp
> Runtime/r3/posix/symlink-posix.cpp
> Additions/linux/sharedfolders/dirops.c
> Additions/common/VBoxGuestLib/VBoxGuestR0LibSharedFolders.c
> But it's not at all clear what
> LOG_GROUPs these files map to.

src/VBox/HostServices/SharedFolders/shfl.h, which is included by the
first two files, contains


for which you need


src/VBox/Runtime/r3/posix/symlink-posix.cpp contains


for which you need


Guest logging inside kernel modules is a rather different kettle of
fish, as it involved quite a bit more infrastructure.  To keep life
simple, you are best to only use release logging if you want to be sure
that it will be visible in the log file, but then it will always go to
the release log file on the host.

Hope that was alright for a start.  Our logging system is rather complex
and it would take a while to describe it comprehensively.

When I get round to it I may create a wiki entry about it.


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