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@csfrancis
Last active May 29, 2023 05:31
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Dump an MRI call stack from gdb
# Updated for Ruby 2.3
string_t = None
def get_rstring(addr):
s = addr.cast(string_t.pointer())
if s['basic']['flags'] & (1 << 13):
return s['as']['heap']['ptr'].string()
else:
return s['as']['ary'].string()
def get_lineno(iseq, pos):
if pos != 0:
pos -= 1
t = iseq['line_info_table']
t_size = iseq['line_info_size']
if t_size == 0:
return 0
elif t_size == 1:
return t[0]['line_no']
for i in range(0, int(t_size)):
if pos == t[i]['position']:
return t[i]['line_no']
elif t[i]['position'] > pos:
return t[i-1]['line_no']
return t[t_size-1]['line_no']
def get_ruby_stacktrace(th=None):
global string_t
try:
control_frame_t = gdb.lookup_type('rb_control_frame_t')
string_t = gdb.lookup_type('struct RString')
except gdb.error:
raise gdb.GdbError ("ruby extension requires symbols")
if th == None:
th = gdb.parse_and_eval('ruby_current_thread')
else:
th = gdb.parse_and_eval('(rb_thread_t *) %s' % th)
last_cfp = th['cfp']
start_cfp = (th['stack'] + th['stack_size']).cast(control_frame_t.pointer()) - 2
size = start_cfp - last_cfp + 1
cfp = start_cfp
call_stack = []
for i in range(0, int(size)):
if cfp['iseq'].dereference().address != 0:
if cfp['pc'].dereference().address != 0:
s = "{}:{}:in `{}'".format(get_rstring(cfp['iseq']['body']['location']['path']),
get_lineno(cfp['iseq']['body'], cfp['pc'] - cfp['iseq']['body']['iseq_encoded']),
get_rstring(cfp['iseq']['body']['location']['label']))
call_stack.append(s)
cfp -= 1
for i in reversed(call_stack):
print(i)
end
@sribalakumar
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@csfrancis On a core dump from a ruby process, is it possible to get the Thread.current[:foo] values ?

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