The test turns on infrun debug, does a stepi while a SIGCHLD is
pending, and checks whether the "random signal" paths in infrun.c are
taken.
On the software single-step variant above, those paths were not taken.
This is a test bug.
The Linux backend short-circuits reporting signals that are set to
pass/nostop/noprint. But _only_ if the thread is _not_
single-stepping. So on hardware-step targets, even though the signal
is set to pass/nostop/noprint by default, the thread is indeed told to
single-step, and so the core sees the signal. On the other hand, on
software single-step architectures, the backend never actually gets a
single-step request (steps are emulated by setting a breakpoint at the
next pc, and then the target told to continue, not step). So the
short-circuiting code triggers and the core doesn't see the signal.
The fix is to make the test be sure the target doesn't bypass
reporting the signal to the core.
Tested on x86_64 Fedora 17, both with and without a series that
implements software single-step for x86_64.
gdb/testsuite/
2014-02-07 Pedro Alves <palves@redhat.com>
* gdb.threads/stepi-random-signal.exp: Set SIGCHLD to print.