On Thu, 18 Dec 2025, Henryk Paluch wrote:
When I run just "glxinfo" on any machine (both virtual and bare metal) on
11.0_BETA - it appears to work but crashes on exit with Signal 11:
[...]
[1] Segmentation fault (core dumped) glxinfo
What is even more puzzling that I'm unable to get decent stack-trace (have
installed all sets including debug).
$ gdb glxinfo glxinfo.core
Reading symbols from glxinfo...
Reading symbols from /usr/libdata/debug//usr/X11R7/bin/glxinfo.debug...
[New process 1979]
Core was generated by `glxinfo'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007b60f1d01eb3 in ?? ()
+bt
#0 0x00007b60f1d01eb3 in ?? ()
#1 0x00007b60f6b1795f in __cxa_finalize (dso=dso@entry=0x0) at
/usr/src/lib/libc/stdlib/atexit.c:222
#2 0x00007b60f6b1753b in exit (status=0) at
/usr/src/lib/libc/stdlib/exit.c:60
#3 0x0000000000b696d2 in ___start (cleanup=<optimized out>,
ps_strings=0x7f7fff6dcfe0) at /usr/src/lib/csu/common/crt0-common.c:375
#4 0x00007f7ff77f08a8 in ?? () from /usr/libexec/ld.elf_so
#5 0x0000000000000001 in ?? ()
#6 0x00007f7fff6dc120 in ?? ()
#7 0x0000000000000000 in ?? ()
+q
Frame 0 crashing and gdb(1) not being able to find the function name for it
has the same cause: it's inside a .so file which's been unmapped by dlclose().
dlclose(), on amd64, calls _fini() in the shared object; which calls
__do_global_dtors_aux(); which calls __cxa_finalize(); this calls the handler
registered by the shared object using atexit(3). __cxa_finalize() will then
NULL the handler so that main() doesn't call it again when _it_ does the final
atexit(3) processing.
But, for some reason, __cxa_finalize() in the shared object never gets called
(and the atexit handlers don't run, of course) and main() then run the atexit
handlers in the _unmapped_ object.
Try the test code below. File a PR too!
Run the program in gdb(1), then when it crashes, compared the address against:
(gdb) info proc mappings
-RVP
---START---
==> Makefile <==
dl-atexit: dl-atexit.c libfoo.so
cc -o dl-atexit dl-atexit.c -Wl,-rpath=$$(pwd)
libfoo.so: libfoo.c
cc -shared -fPIC -o libfoo.so libfoo.c
run: dl-atexit
./dl-atexit
clean:
rm -f dl-atexit *.so *.core
==> dl-atexit.c <==
#include <dlfcn.h>
#include <stdio.h>
int
main(void)
{
void *h = dlopen("libfoo.so", RTLD_LOCAL | RTLD_LAZY);
if (h == NULL) {
fprintf(stderr, "dlopen(): %s\n", dlerror());
return 1;
}
void (*foo)(void) = dlsym(h, "foo");
if (foo == NULL) {
fprintf(stderr, "dlsym(foo): %s\n", dlerror());
return 1;
}
printf("%s: calling foo()\n", __func__);
foo();
printf("%s: calling dlclose()\n", __func__);
dlclose(h);
printf("%s: exiting...\n", __func__);
return 0;
}
==> libfoo.c <==
#include <stdio.h>
#include <stdlib.h>
static void
die(void)
{
printf("%s: atexit handler\n", __func__);
}
void
foo(void)
{
atexit(die);
printf("%s: atexit handler die() @ %p\n", __func__, die);
}
---END---
