On 31 Jan 2014, at 21:35, Dimitry Andric <[email protected]> wrote: ... > Hmm, at least I can reproduce it, but the stack trace does not tell me that > much: > > (gdb) run > Starting program: > /usr/work/share/dim/ports/net/avahi-app/work/avahi-0.6.31/./avahi-utils/.libs/avahi-browse > [New LWP 101263] > > Program received signal SIGSEGV, Segmentation fault. > [Switching to LWP 101263] > _thr_cancel_enter (curthread=0x0) at > /share/dim/src/freebsd/head-clang34/lib/libthr/thread/thr_cancel.c:141 > 141 curthread->cancel_point = 1; > (gdb) bt > #0 _thr_cancel_enter (curthread=0x0) at > /share/dim/src/freebsd/head-clang34/lib/libthr/thread/thr_cancel.c:141 > #1 0x280d0f2d in __open (path=<optimized out>, flags=<optimized out>) > at /share/dim/src/freebsd/head-clang34/lib/libthr/thread/thr_syscalls.c:390 > #2 0x280fef46 in __guard_setup () at > /share/dim/src/freebsd/head-clang34/gnu/lib/libssp/../../../contrib/gcclibs/libssp/ssp.c:72 > #3 0x280ff182 in ?? () from /lib/libssp.so.0 > #4 0x280fe749 in _init () from /lib/libssp.so.0 > #5 0x00000000 in ?? () > (gdb) up > #1 0x280d0f2d in __open (path=<optimized out>, flags=<optimized out>) > at /share/dim/src/freebsd/head-clang34/lib/libthr/thread/thr_syscalls.c:390 > 390 _thr_cancel_enter(curthread); > (gdb) up > #2 0x280fef46 in __guard_setup () at > /share/dim/src/freebsd/head-clang34/gnu/lib/libssp/../../../contrib/gcclibs/libssp/ssp.c:72 > 72 fd = open ("/dev/urandom", O_RDONLY); > > E.g., __guard_setup() tries to get some random bytes from /dev/urandom > (probably for the stack canaries), libthr considers this to be a thread > cancellation point, but for some reason the current thread is zeroed > out? I don't think this is ever supposed to happen... :-)
So avahi-browse gets linked as follows (wrapped a little for clarity):
cc -I.. "-DDEBUG_TRAP=__asm__(\"int \$3\")"
-DDATABASE_FILE=\"/usr/local/lib/avahi/service-types.db\" -O2 -pipe
-march=corei7 -g -fno-strict-aliasing -fstack-protector -std=c99 -Wall
-W -Wextra -pedantic -pipe -Wformat -Wold-style-definition
-Wdeclaration-after-statement -Wfloat-equal -Wmissing-declarations
-Wmissing-prototypes -Wstrict-prototypes -Wredundant-decls
-Wmissing-noreturn -Wshadow -Wendif-labels -Wpointer-arith
-Wbad-function-cast -Wcast-qual -Wcast-align -Wwrite-strings
-fdiagnostics-show-option -Wno-cast-qual -fno-strict-aliasing
-o .libs/avahi-browse avahi_browse-avahi-browse.o avahi_browse-sigint.o
avahi_browse-stdb.o -L/usr/local/lib
../avahi-client/.libs/libavahi-client.so /usr/local/lib/libdbus-1.so
-lpthread
/usr/work/share/dim/ports/net/avahi-app/work/avahi-0.6.31/avahi-common/.libs/libavahi-common.so
../avahi-common/.libs/libavahi-common.so /usr/local/lib/libgdbm.so -lssp
/usr/local/lib/libintl.so -pthread -Wl,-rpath -Wl,/usr/local/lib
This executable segfaults, and has the NEEDED libs in the following
order:
.libs/avahi-browse:
libavahi-client.so.3 => /usr/local/lib/libavahi-client.so.3 (0x28076000)
libdbus-1.so.3 => /usr/local/lib/libdbus-1.so.3 (0x28085000)
libthr.so.3 => /lib/libthr.so.3 (0x280cf000)
libavahi-common.so.3 => /usr/local/lib/libavahi-common.so.3 (0x280f1000)
libgdbm.so.4 => /usr/local/lib/libgdbm.so.4 (0x280fc000)
libssp.so.0 => /lib/libssp.so.0 (0x28106000)
libintl.so.9 => /usr/local/lib/libintl.so.9 (0x28109000)
libc.so.7 => /lib/libc.so.7 (0x28112000)
When I remove the -lssp from the above linking command line, it is
automatically induced anyway, but the executable then gets the following
NEEDED libs order:
.libs/avahi-browse:
libavahi-client.so.3 => /usr/local/lib/libavahi-client.so.3 (0x28076000)
libdbus-1.so.3 => /usr/local/lib/libdbus-1.so.3 (0x28085000)
libthr.so.3 => /lib/libthr.so.3 (0x280cf000)
libavahi-common.so.3 => /usr/local/lib/libavahi-common.so.3 (0x280f1000)
libgdbm.so.4 => /usr/local/lib/libgdbm.so.4 (0x280fc000)
libintl.so.9 => /usr/local/lib/libintl.so.9 (0x28106000)
libc.so.7 => /lib/libc.so.7 (0x2810f000)
libssp.so.0 => /lib/libssp.so.0 (0x28263000)
E.g. libssp.so.0 is now located at the end of the list. And _this_
executable runs fine...!
If anyone has a good explanation for this, I would be dying to know. :-)
-Dimitry
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