gdb: prevent assertion after 'set debug breakpoint on'
Turns out that using 'set debug breakpoint on' will trigger an
assertion for 'catch' style breakpoints, e.g.:
(gdb) file /tmp/hello.x
Reading symbols from /tmp/hello.x...
(gdb) catch exec
Catchpoint 1 (exec)
(gdb) set debug breakpoint on
(gdb) start
[breakpoint] dump_condition_tokens: Tokens: { INFERIOR: "1" }
Temporary breakpoint 2 at 0x401198: file /tmp/hello.c, line 18.
[breakpoint] update_global_location_list: insert_mode = UGLL_MAY_INSERT
Starting program: /tmp/hello.x
[breakpoint] update_global_location_list: insert_mode = UGLL_MAY_INSERT
../../gdb-16.1/gdb/gdbarch-gen.c:1764: internal-error: gdbarch_addr_bit: Assertion `gdbarch != NULL' failed.
.... etc ...
The problem is that catch breakpoints don't set the
bp_location::gdbarch member variable, they a "dummy" location added
with a call to add_dummy_location (breakpoint.c).
The breakpoint_location_address_str function (which is only used for
breakpoint debug output) relies on bp_location::gdbarch being set in
order to call the paddress function.
I considered trying to ensure that the bp_location::gdbarch variable
is always set to sane value. For example, in add_dummy_location I
tried copying the gdbarch from the breakpoint object, and this does
work for the catchpoint case, but for some of the watchpoint cases,
even the breakpoint object has no gdbarch value set.
Now this seemed a little suspect, but, the more I thought about it, I
wondered if "fixing" the gdbarch was allowing me to solve the wrong
problem.
If the gdbarch was set, then this would allow us to print the address
field of the bp_location, which is going to be 0, after all, as this
is a dummy location, which has no address.
But does it really make sense to print the address 0? For some
targets, 0 is a valid address. But that wasn't an address we actually
selected, it's just the default value for dummy locations.
And we already have a helper function bl_address_is_meaningful, which
returns false for dummy locations.
So, I propose that in breakpoint_location_address_str, we use
bl_address_is_meaningful to detect dummy locations, and skip the
address printing code in that case.
For testing, I temporarily changed insert_bp_location so that
breakpoint_location_address_str was always called, even when
breakpoint debugging was off. I then ran the whole testsuite.
Without the fixes included in this commit I saw lots of assertion
failures, but with the fixes from this commit in place, I now see no
assertion failures.
I've added a new test which reveals the original assertion failure.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
4 files changed
