...under gdb, the assertion also fails; but if I set a bp, e.g.

(gdb...

...is normal.

This explains why my earlier gdb session revealed that the error messages the...

...something like bpf or gdb to watch it manually (if possible). GDB supports d demangling.

...But I did set a breakpoint in gdb at the place where the error messages...

...not occurring -- a Heisenbug.  But working with gdb, I found that the account structs after...

...http://www.gnu.org/software/gdb/bugs/>.
  | Find the GDB manual and other documentation...

...GDB at some debug step it calls D symbol from initial C code. Then GDB...

...gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0x00005555558b496c in simplify_code(code*) ()
(gdb...

Try "handle SIGUSR1 nostop noprint" and "handle SIGUSR2 nostop noprint" in gdb.

...x86_64-linux-gnu/libc.so.6
(gdb) where
#0  0x00007ffff5d99361 in clock_nanosleep () from...