gcc linked -static segfaults with bogus syscall on recent snapshot

[j]

For the August 11 snapshot

ry$ sysctl kern.version
kern.version=OpenBSD 6.7-current (GENERIC.MP) #22: Tue Aug 11 21:29:51 
MDT 2020
    dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
ry$ egcc --version
egcc (GCC) 8.3.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is 
NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR 
PURPOSE.


ry$ cat mytls.c
 __thread int a; int b; int main() { return a = b; }
ry$ egcc -o mytls -static mytls.c
ry$ ./mytls
Segmentation fault (core dumped)
ry$ grep mytls /var/log/messages
...[snip]...
Aug 13 15:44:40 ry /bsd: [mytls]36048/435394 pc=5951167a inside 
27732e000-27733c000: bogus syscall


For the Jun 15 snapshot, all is well:

snap1$ sysctl kern.version
kern.version=OpenBSD 6.7-current (GENERIC.MP) #272: Mon Jun 15 01:54:58 
MDT 2020
    dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP

snap1$ egcc --version
egcc (GCC) 8.3.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is 
NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR 
PURPOSE.

snap1$ cat mytls.c
 __thread int a; int b; int main() { return a = b; }
snap1$ egcc -o mytls mytls.c -O2 -static
snap1$ mytls
snap1$


And the static image is different:

snap1$ ldd mytls
mytls:
        Start            End              Type  Open Ref GrpRef Name
        00000fda3f626000 00000fda3f648000 dlib  1    0   0      
/home/j/tls/mytls
on the older snapshot, and

ry$ ldd mytls
mytls:
        Start            End              Type  Open Ref GrpRef Name
        000004822c606000 000004822c62a000 exe   1    0   0      mytls
        0000048524b42000 0000048524b42000 ld.so 0    1   0      
/usr/libexec/ld.so
on the newer snapshot.

These are two different machines, snap1 is Dell workstation,
E7400 Core 2 Duo, and ry is Ryzen 3700 8-core.

The example code is scooped from the gcc configure scripts. A gcc build
provokes this behaviour (using this code fragment) when building gcc for
these libraries:

   libstdc++-v3
   libobjc
   libitm
   libgomp (which is me adding OMP to gcc)

It seems to be only for TLS (thread-local-storage) tests, iiuc.

clang does not show this behaviour.


John