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Lilypond loglevels & debug output
Lilypond loglevels & debug output
Fri, 5 Aug 2011 18:48:15 +0200
KMail/1.13.6 (Linux/2.6.38-11-generic; KDE/4.7.0; i686; ; )
(This is a pretty long post, detailling my thoughts about the logging
"framework". The first part describes the planned loglevels, so that
documentation writers have all information. However, I'm most interested in
your thoughts about the future directions, which are given in the second half
of the mail, since they can really make the life of us contributors much
easier, also for the build system!)
As you know, I'm working on implementing proper loglevels into the lilypond
binary to allow fine-grained control over the output of lilypond. My current
patch (available at Rietveld: http://codereview.appspot.com/4822055/ )
currently implements the following features:
-) --loglevel=LEVEL cmd line switch with possible levels (case-insensitive,
might even be truncated):
o) NONE: No output at all, return code of binary !=0 for an error
o) ERROR: Only print error messages, no warnings or progress
o) WARNING: Only print errors & warnings, no progress
o) BASIC_PROGRESS: error, warnings and basic progress (file name,
o) PROGRESS: errors, warnings, progress (i.e. the current output)
o) DEBUG: print full debug output (i.e. current --verbose output)
The first 5 levels (NONE to PROGRESS) are indented mainly for users, who
don't want the whole progress output (because e.g. they call lilypond in
scripts, or process many files at once, where they just want an overview
over the warnings/errors). The rest (DEBUG and maybe finer-grained debug
messages, see below) are intended for developers, who want to know about
the details of a lilypond run.
Default is PROGRESS, i.e. the current output.
Truncated strings for loglevels need to be at least: NONE, ERR, WARN,
BASIC, PROG and DEBUG. (i.e. it's also okay to write WARNINGS or WARN or
even WARN_ME_ABOUT_XXXX instead of WARNING). The comparison is done case-
insensitive with only the first 3-5 characters.
-) New cmd line switch --silent, which is equal to --loglevel=ERROR
-) Environment variables LILYPOND_VERBOSE (sets --verbose) and
LILYPOND_DEBUGLEVEL are processed before the cmd line options to specify
a different default debuglevel. An explicit cmd line option --loglevel,
--silent or --verbose overrides this.
So you can now set a loglevel of WARNING globally by
and any call to lilypond that does not use an explicit --loglevel will
only print warnings.
Order of evaluation (later ones override): LILYPOND_VERBOSE,
LILYPOND_LOGLEVEL, explicit cmd line args (--loglevel, --silent, --verbose)
-) A loglevel can also be given as a numeric value (undocumented), which
specifies the loglevel as a bitmask (i.e. if a developer wants to test
just warnings, but no errors). This might also be used for finer-grained
debug output for developers, see below
-) The C interface (in warn.cc), the C++ interface (in input.cc, which prints
out exact location if the input is known) and the Guile interface
(previously in general-scheme.cc, moved to warn-scheme.cc) to the log
functions are basically unchanged:
o) error (string); // Fatal error, exits lilypond!
o) programming_error (string);
o) non_fatal_error (string);
o) warning (string);
o) successful (string);
o) progress_indication (string, bool newline = false);
o) message (string, bool newline = true);
o) debug_output (string, bool newline = true);
The newline argument specifies whether the message should always start on a
new line or not (i.e. continue a previous message on the same line, which
is the default for progress_indication!)
o) Input::error (string) // Error, does NOT exit lilypond immediately!
o) Input::programming_error (string)
o) Input::non_fatal_error (string)
o) Input::warning (string)
o) Input::message (string)
o) Input::debug_output (string)
o) (ly:error message args) ;; Fatal error, exits lilypond!
o) (ly:programming-error message args)
o) (ly:warning message args)
o) (ly:success message args)
o) (ly:progress message args)
o) (ly:message message args)
o) (ly:debug message args)
However, there are some more things that I would like to implement:
-) Finer-grained debug output. We can do this by either adding another
--debuglevel cmd line switch (with a binary bitmask as value), or by
using the upper 8 bits of the loglevel as a bitmask.
The debug functions (debug_output (string), Input::debug_output (string)
and (ly:debug message args) would then get a first argument defining the
type of debug output, e.g.
debug_output (DEBUG_FONTS, "[" + string (pango_fn), true);
The loglevel or debuglevel (whichever we choose) then needs to be given as
a number, though, like --loglevel=4095 (i.e. 00011111111111 in binary). Do
you have a better idea to specify different debug areas?
--loglevel=DEBUG would print ALL debug messages of all debug areas.
-) Guile functions that also print out the location of a warning/error/message
Currently, only the methods of the Input class print out the location of
the code that triggered the output. Currently, we have two scm functions
(version-not-seen-message and old-relative-not-used-message) that mimic
this behavior by printing a normal message with the string "file:line:
warning: " prepended. This breaks the loglevels, as it is a warning,
disguised as a normal progress message...
-) Add a cmd line option to optionally print out the different types of
message to different file descriptors (e.g. errors to stderr, warnings to
descriptor 3, progress to descriptor 4 and debug output to descriptor 5).
This is needed for the build system to be able to distinguish warnings from
progress messages, etc.
The build system could then use proper I/O redirections and piping to
e.g. echo everything from the error and warnings descriptors on the
console, write everything from error, warning and progress descriptors
to a log file and all debug messages to a differrent debug log file.
Without this switch, it is basically impossible to distinguish error
messages from debug output, once lilypond printed the output.
What do you think?
Reinhold Kainhofer, address@hidden, http://reinhold.kainhofer.com/
* Financial & Actuarial Math., Vienna Univ. of Technology, Austria
* http://www.fam.tuwien.ac.at/, DVR: 0005886
* LilyPond, Music typesetting, http://www.lilypond.org
- Lilypond loglevels & debug output,
Reinhold Kainhofer <=