Re: [PATCH 1/2] Fix running to breakpoint set in inline function by lineno/address

Joel Brobecker
2018-06-28T17:32:59Z

> Commit 61b04dd04ac2 ("Change inline frame breakpoint skipping logic
> (fix gdb.gdb/selftest.exp)") caused a GDB crash when you set a
> breakpoint by line number in an inline function, and then run to the
> breakpoint:
>
> $ gdb -q test Reading symbols from test...done.
> (gdb) b inline-break.c:32
> Breakpoint 1 at 0x40062f: file inline-break.c, line 32.
> (gdb) run
> Starting program: /[...]/test
> [1] 75618 segmentation fault /[...]/gdb -q test
>
> The problem occurs because we assume that a bp_location's symbol is
> not NULL, which is not true when we set the breakpoint with a linespec
> location:
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x00000000006f42bb in stopped_by_user_bp_inline_frame (
> stop_chain=<optimized out>, frame_block=<optimized out>)
> at gdb/inline-frame.c:305
> 305 && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
> (gdb) p loc->symbol
> $1 = (const symbol *) 0x0
>
> The same thing happens if you run to a breakpoint set in an inline
> function by address:
>
> (gdb) b *0x40062f
> Breakpoint 3 at 0x40062f: file inline-break.c, line 32.
>
> To fix this, add a null pointer check, to avoid the crash, and make it
> so that if there's not symbol for the location, then we present the
> stop at the inline function. This preserves the previous behavior
> when e.g., setting a breakpoint by address, with "b *ADDRESS".
>
> gdb/ChangeLog:
> yyyy-mm-dd Pedro Alves <palves@redhat.com>
>
> * inline-frame.c (stopped_by_user_bp_inline_frame): Return
> true if the the location has no symbol.
>
> gdb/testsuite/ChangeLog:
> yyyy-mm-dd Pedro Alves <palves@redhat.com>
>
> * gdb.opt/inline-break.c (func1): Add "break here" marker.
> * gdb.opt/inline-break.exp: Test setting breakpoints by line
> number and address and running to them.

Thanks, Pedro. I had a look, and FWIW, the patch looks good to me.

--
Joel