Python Symbol API question/weirdness

[Evan Driscoll <evaned@gmail.com>]

[I wrote most of this with 7.11, but I tried again with 8.0 and still
have the same problem. See below for more.]


I've got a toy program (can send out source and/or binary if it'd be
helpful) that calls raise(SIGTRAP) in it.

At that point, I can ask for a backtrace:

(gdb) bt
#0  0x00007ffff7a43428 in __GI_raise (sig=sig@entry=5)
...

and then use 'info symbol' to get some information based on that
address, and cross-check it with the symbol name that it gives back:

(gdb) info symbol  0x00007ffff7a43428
raise + 56 in section .text of /lib/x86_64-linux-gnu/libc.so.6
(gdb) info symbol raise
raise in section .text of /lib/x86_64-linux-gnu/libc.so.6
(gdb) python print(gdb.parse_and_eval("raise"))
{<text variable, no debug info>} 0x7ffff7a433f0 <__GI_raise>

I'm not sure the following is relevant, but just in case:

(gdb) print &raise
$2 = (<text variable, no debug info> *) 0x7ffff7a433f0 <__GI_raise>
(gdb) print &__GI_raise
$3 = (int (*)(int)) 0x7ffff7a433f0 <__GI_raise>


However, I can't look up that symbol in Python using lookup_global_symbol:

(gdb) python print(gdb.lookup_symbol("raise"))
(None, False)
(gdb) python print(gdb.lookup_global_symbol("raise"))
None

Setting a domain doesn't seem to help:

>>> ds = [gdb.SYMBOL_UNDEF_DOMAIN,
...       gdb.SYMBOL_VAR_DOMAIN,
...       gdb.SYMBOL_STRUCT_DOMAIN,
...       gdb.SYMBOL_LABEL_DOMAIN,
...       gdb.SYMBOL_VARIABLES_DOMAIN,
...       gdb.SYMBOL_FUNCTIONS_DOMAIN,
...       gdb.SYMBOL_TYPES_DOMAIN,
...       ]
>>> for d in ds: print(gdb.lookup_global_symbol("raise", d))
None
None
None
None
None
None
None

Does anyone have any idea what might be going on? I think I don't
actually need this to work, but I am curious what is going on. Maybe
something with symbol aliases?

With GDB 8.0 instead of 7.11, things change slightly but remain
largely the same. __GI_raise never shows up -- the backtrace just says
"raise" instead, and 'print __GI_raise' and 'info symbol __GI_raise'
both produce errors.

Thanks,
Evan