How to set breakpoints on future shared libraries with a command flag

Question

I\'m trying to automate a gdb session using the --command flag. I\'m trying to set a breakpoint on a function in a shared library (the Unix equivalent of a DLL)

Answer 1

With no symbols.

objdump -t /lib/libacl.so
SYMBOL TABLE:
no symbols
objdump -T /lib/libacl.so
...
00002bd0 g    DF .text  000000d0  ACL_1.0     acl_delete_entry
...


(gdb) break 0x0002bd0 

(gdb) x/20i acl_delete_entry
0x2bd0 <acl_delete_entry>:      stwu    r1,-32(r1)
0x2bd4 <acl_delete_entry+4>:    mflr    r0
0x2bd8 <acl_delete_entry+8>:    stw     r29,20(r1)
0x2bdc <acl_delete_entry+12>:   stw     r30,24(r1)
0x2be0 <acl_delete_entry+16>:   mr      r29,r4
0x2be4 <acl_delete_entry+20>:   li      r4,28972

Answer 2

Replying to myself, I'd like to give the answer that someone gave me on IRC:

(gdb) apropos pending
actions -- Specify the actions to be taken at a tracepoint
set breakpoint -- Breakpoint specific settings
set breakpoint pending -- Set debugger's behavior regarding pending breakpoints
show breakpoint -- Breakpoint specific settings
show breakpoint pending -- Show debugger's behavior regarding pending breakpoints

And so set breakpoint pending on does the trick; it is used in cmds.gdb like e.g.

set breakpoint pending on
break <source file name>:<line number>

Answer 3

OT: In terminal it would look like this to debug Caja in one line:

gdb -ex "set breakpoint pending on" -ex "break gdk_x_error" -ex run --args caja --sync