source: trunk/third/xscreensaver/README.debugging @ 20148

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2                              XScreenSaver
3
4              a handy guide for creating useful bug reports
5
6                                --------
7
8    It's hard to imagine, but sometimes, xscreensaver has bugs.  This
9    document gives some hints for isolating them; the more information
10    you can give me about the problem, the better the odds that I'll be
11    able to fix it.  But, if you don't have time to go through these
12    steps, please report the bug anyway -- even vague bug reports can
13    be better than no bug report at all.
14
15                                --------
16STEP ZERO:
17
18    What are you doing here?  Go read README, and then the man page.
19
20STEP ZERO, PART TWO:
21
22    Do you have the most recent version?  Go make sure.
23    http://www.jwz.org/xscreensaver/.
24
25COMPILATION PROBLEMS:
26
27    If you get an error running the `configure' script, the first thing
28    you should try is deleting the `config.cache' file, and running again.
29    If that doesn't fix it, the information I'll need to see to make
30    sense of the problem is the following:
31
32        *  everything printed to stderr/stdout when you first ran
33           ./configure;
34
35        *  the contents of the `config.log' file.
36
37    Make sure you blow away the config.cache file before regenerating
38    this info, or else the `config.log' file will be mostly empty/useless.
39
40    Experience seems to show that the most common configure problem is
41    that sites have gcc installed, but installed improperly.  The
42    configure script will always try to use gcc in preference to another
43    compiler if gcc exists, so if gcc exists but is broken, it won't
44    work.  Your options are:
45
46        *  get someone to fix the gcc installation;
47
48        *  rearrange your $PATH so that the broken gcc is not on it;
49
50        *  or pass $CC in the environment, like so:
51
52              csh:  setenv CC cc ; ./configure
53              sh:   CC=cc ; ./configure
54
55    Before doing this, you'll need to nuke `config.cache'.
56
57    If you get errors about not being able to find Gtk, then perhaps
58    the problem is that you don't have some kind of ``development
59    option'' installed.
60
61RUN-TIME PROBLEMS:
62
63    For runtime errors, it's important to keep in mind that there are
64    two parts to xscreensaver: there is the screensaver driver process
65    (the daemon that detects idleness, deals with locking, and launches
66    the demos); and there are the demos themselves (independent programs
67    that draw pretty pictures.)
68
69        *  Compile with `make CFLAGS=-g' (so that if you get a core
70           dump, there will be debugging info in it.)
71
72        *  What platform are you running on?  What does the included
73           `./config.guess' shell script print?
74
75        *  Is the problem in the driver (`xscreensaver'), the GUI
76           (`xscreensaver-demo'), or in the graphics hacks?
77
78        *  If the problem is in the GUI, was it built using Gtk, Motif,
79           or Lesstif?  Which version?
80
81        *  If the problem is in one (or more) of the hacks, which ones?
82           If you're not sure, try running `xscreensaver-demo' to go
83           through the list of them and see which work and which don't.
84
85        *  Does the problem occur when running that hack by hand, in
86           its own window (i.e., when started with no command-line args)?
87
88        *  Does the problem occur when running that hack by hand, on
89           the root window (i.e., when started with the `-root' option)?
90
91        *  IMPORTANT: What visual are you using?  Send the output of
92           the `xdpyinfo' command.
93
94        *  Does the problem go away if you give the program a different
95           `-visual' argument?  (For example, `-visual pseudocolor' or
96           `-visual truecolor'.)
97
98        *  IMPORTANT: What exactly goes wrong?  No, I don't know what
99           you mean by "crash".  Does it print an "X Error" and exit?
100           Does it dump core?  Does it go into a loop?
101
102        *  If it dumps core, what does the core file say?  Run the
103           program under a debugger, and show me the stack trace.
104           To extract a stack trace from a core file with gdb, do this:
105
106              gdb ./the-program ./core
107              bt
108
109           To extract a stack trace from a core file with dbx, do this:
110
111              dbx ./the-program ./core
112              where
113
114           If the bottom few lines of the output don't include the functions
115           `main_loop()' and `main()', then something went wrong, and the
116           core file is bogus.  If the lines it prints out contain only
117           question marks, then the core file is bogus.  Are you sure the
118           core file came from that program?  Did you compile with -g, as
119           explained above?  If you don't compile with -g, the core file
120           won't have any information in it.
121
122           Never ever ever mail me (or anyone) a core file.  They are huge,
123           and are only meaningful on the machine that generated them, with
124           the exact executable that generated them, neither of which anyone
125           but you has access to.  Don't mail me a core file unless you're
126           also planning on mailing me your computer.
127
128        *  If it gets an X error, where did it come from?  Run
129           xscreensaver with the `-sync' command-line option.  When `-sync'
130           is used, X errors will cause xscreensaver to dump a core file.
131           Look at the core file with a debugger and show me the stack trace,
132           as above: I need to know where in xscreensaver that X error came
133           from.
134
135    If the problem is with the xscreensaver process itself, or if you
136    can't figure out which demo is causing the problem, or if you can't
137    reproduce the problem in isolation, then you will need to turn on
138    and examine the debugging output of the driver process.
139
140        *  Start `xscreensaver' with the command-line arguments
141
142              -verbose -no-capture
143
144           This will cause it to write a lot of debugging info to the stderr
145           of the xscreensaver process (the `-verbose' option turns on the
146           diagnostics; the `-no-capture' option prevents the data from being
147           displayed on the screensaver window as well.)
148
149        *  If the problem is intermittent, you might want to capture the
150           log information to a file and examine it later.  For example,
151           you could start it from your login script like this (csh syntax):
152
153               xscreensaver -sync -verbose -no-capture >>& saverlog &
154
155        *  Hackers only: If you're feeling adventurous enough to run gdb
156           on the xscreensaver driver process itself, make sure you've
157           read the commentary at the top of xscreensaver.c.
158
159-----------------------------------------------------------------------------
160                                             http://www.jwz.org/xscreensaver/
161                                                 Jamie Zawinski <jwz@jwz.org>
162-----------------------------------------------------------------------------
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