strange libc symbol renaming issue

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

Hello,
I've a very strange symbol renaming issue on NetBSD 8.0/amd64:
syslog-ng dies with a bad syscall signal, ktrace reveals that it
called compat_13_sigaction13, just after properly calling __sigprocmask14.
gdb on the core dump shows:
Core was generated by `syslog-ng'.
Program terminated with signal SIGSYS, Bad system call.
#0  0x00007747ad46e74a in sigaction () from /usr/lib/libc.so.12
(gdb) up
#1  0x00007747b0e38f38 in g_process_perform_supervise () at lib/gprocess.c:1087
1087      sigaction(SIGHUP, &sa, NULL);
(gdb) 

but gprocess.c properly includes signal.h, there was no warning at link time,
and disasembling the function confirms it:
   0x00007747b0e38f08 <+143>:   movq   $0x0,0x58(%rsp)
   0x00007747b0e38f11 <+152>:   movq   $0x0,0x60(%rsp)
   0x00007747b0e38f1a <+161>:   movq   $0x0,0x68(%rsp)
   0x00007747b0e38f23 <+170>:   movq   $0x1,0x50(%rsp)
   0x00007747b0e38f2c <+179>:   xor    %edx,%edx
   0x00007747b0e38f2e <+181>:   mov    $0x1,%edi
   0x00007747b0e38f33 <+186>:   callq  0x7747b0e2f700 <__sigaction14@plt>
=> 0x00007747b0e38f38 <+191>:   mov    $0x1,%ebp
   0x00007747b0e38f3d <+196>:   lea    0x4c(%rsp),%r15
   0x00007747b0e38f42 <+201>:   lea    0x41378(%rip),%r14        # 0x7747b0e7a2c1

From here gdb seems lost; I'm working on a core dump as this all happens
after a fork so I can't work on it live:
(gdb) disas 0x7747b0e2f700
Dump of assembler code for function __sigaction14@plt:
   0x00007747b0e2f700 <+0>:     jmpq   *0x2834a2(%rip)        # 0x7747b10b2ba8
   0x00007747b0e2f706 <+6>:     pushq  $0x4e5
   0x00007747b0e2f70b <+11>:    jmpq   0x7747b0e2a8a0
0x7747b10b2ba8 is in _GLOBAL_OFFSET_TABLE_
(gdb) x/lx 0x7747b10b2ba8
0x7747b10b2ba8: 0xb0e46527
(gdb) disas 0xb0e46527
No function contains specified address.
(gdb) x/i 0xb0e46527
   0xb0e46527:  Cannot access memory at address 0xb0e46527

Any idea what could cause a program actually calling explicitely __sigaction14
to end up in the compat sigaction ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--