But do still print a full backtrace, on platforms where that's
supported.
This commit follows the spirit of Novell's libxcb-sloppy-lock.diff.
I strongly opposed proposals like this one for a long time. Originally I
had a very good reason: libX11, when compiled to use XCB, would crash
soon after a locking correctness violation, so it was better to have an
informative assert failure than a mystifying crash soon after.
It took some time for me to realize that I'd changed the libX11
implementation (for unrelated reasons) so that it could survive most
invalid locking situations, as long as it wasn't actually being used
from multiple threads concurrently.
The other thing that has changed is that most of the code with incorrect
locking has now been fixed. The value of the assert is accordingly
lower.
However, remaining broken callers do need to be fixed. That's why libXCB
will still noisily print a stacktrace (if possible) on each assertion
failure, even when assert isn't actually invoked to abort() the program;
and that's why aborting is still default. This environment variable is
provided only for use as a temporary workaround for broken applications.
Signed-off-by: Jamey Sharp <jamey@minilop.net>
Acked-by: Josh Triplett <josh@freedesktop.org>
As you know there are some nasty libs / apps doing locking
incorrectly. In order to improve the information given to the user
when he encounters such a situation (people don't run apps in gdb
normally) I created the patch attached.
It's very non-intrusive (and affects only xlib/xcb, Josh told me on
irc that it could be useful for other areas too, personally I don't
think that it's really needed at other places ...).
Some same outputs and the discussion of them:
lxuser@pdln:/tmp$ ./main
Got a backtrace:
#0 /tmp/usr/lib/libxcb-xlib.so.0 [0xb7f9d728]
#1 /tmp/usr/lib/libxcb-xlib.so.0(xcb_xlib_unlock+0x31) [0xb7f9d861]
#2 ./test.so(function_a+0x11) [0xb7f9f3fd]
#3 ./test.so(function_b+0x11) [0xb7f9f410]
#4 ./main [0x80484a7]
#5 /lib/libc.so.6(__libc_start_main+0xdc) [0xb7e60ebc]
#6 ./main [0x80483f1]
main: xcb_xlib.c:82: xcb_xlib_unlock: Assertion `c->xlib.lock' failed.
Aborted
That's kinda the normal situation.
lxuser@pdln:/tmp$ ./main
Got a backtrace:
#0 /tmp/usr/lib/libxcb-xlib.so.0 [0xb7f90728]
#1 /tmp/usr/lib/libxcb-xlib.so.0(xcb_xlib_unlock+0x31) [0xb7f90861]
#2 /tmp/test.so [0xb7f923cd]
#3 /tmp/test.so(function_b+0x11) [0xb7f923e0]
#4 ./main [0x80484ab]
#5 /lib/libc.so.6(__libc_start_main+0xdc) [0xb7e53ebc]
#6 ./main [0x80483f1]
main: xcb_xlib.c:82: xcb_xlib_unlock: Assertion `c->xlib.lock' failed.
Aborted
There are two possible reasons that the name doesn't appear in #2:
a) a hidden symbol or a symbol with statical linkage in a library
b) a symbol in an app not compiled with -rdynamic.
But in both cases you still know _where_ the caller is.
Note that in this example test.so was compiled with
-fomit-frame-pointer; this isn't an issue as _one_ (= the caller)
stack trace is still valid (as long as you don't have the insane idea
to compile xcb with -fo-f-p).
Another issue that may appear is "tail call elimination" (some entries
are mysteriously missing; this is quite ugly, but you still get enough
information so that you can do something useful with the issue e.g. by
disassembling the relevant parts with gdb).
Signed-off-by: Jamey Sharp <jamey@minilop.net>
Rename API to follow a new naming convention:
* XCB_CONSTANTS_UPPERCASE_WITH_UNDERSCORES
* xcb_functions_lowercase_with_underscores
* xcb_types_lowercase_with_underscores_and_suffix_t
* expand all abbreviations like "req", "rep", and "iter"
Word boundaries for the names in the protocol descriptions fall:
* Wherever the protocol descriptions already have an underscore
* Between a lowercase letter and a subsequent uppercase letter
* Before the last uppercase letter in a string of uppercase letters followed
by a lowercase letter (such as in LSBFirst between LSB and First)
* Before and after a string of digits (with exceptions for sized types like
xcb_char2b_t and xcb_glx_float32_t to match the stdint.h convention)
Also fix up some particular naming issues:
* Rename shape_op and shape_kind to drop the "shape_" prefix, since otherwise
these types end up as xcb_shape_shape_{op,kind}_t.
* Remove leading underscores from enums in the GLX protocol description,
previously needed to ensure a word separator, but now redundant.
This renaming breaks code written for the previous API naming convention. The
scripts in XCB's tools directory will convert code written for the old API to
use the new API; they work well enough that we used them to convert the
non-program-generated code in XCB, and when run on the old program-generated
code, they almost exactly reproduce the new program-generated code (modulo
whitespace and bugs in the old code generator).
Authors: Vincent Torri, Thomas Hunger, Josh Triplett
Jamey Sharp
Josh Triplett
Christoph Pfister