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Re: [PATCH v2] Don't lose language determined from the "main" name (fix gdb.ada/minsyms.exp)
- From: Sergio Durigan Junior <sergiodj at redhat dot com>
- To: Pedro Alves <palves at redhat dot com>
- Cc: gdb-patches at sourceware dot org, Joel Brobecker <brobecker at adacore dot com>
- Date: Tue, 21 Nov 2017 12:29:49 -0500
- Subject: Re: [PATCH v2] Don't lose language determined from the "main" name (fix gdb.ada/minsyms.exp)
- Authentication-results: sourceware.org; auth=none
- References: <1511284814-25508-1-git-send-email-palves@redhat.com>
On Tuesday, November 21 2017, Pedro Alves wrote:
> New in v2:
> - completely different solution/implementation. avoids selecting a
> frame in the first place.
For the record: this LGTM.
Thanks,
> gdb.ada/minsyms.exp fails like this here:
>
> FAIL: gdb.ada/minsyms.exp: print integer(some_minsym)
> FAIL: gdb.ada/minsyms.exp: print /x integer(&some_minsym)
>
> The problem is that if you have debug info for glibc, GDB switches the
> current language to C before it reaches the program's entry point, and
> then Ada's cast syntax doesn't work when the current language is C:
>
> print integer(some_minsym)
> A syntax error in expression, near `some_minsym)'.
> (gdb) FAIL: gdb.ada/minsyms.exp: print integer(some_minsym)
>
> I first thought of doing "set language ada" in the testcase, but
> looking deeper, I realized that before running to main, GDB knows the
> program is Ada, determined by reading __gnat_ada_main_program_name,
> via set_initial_language->main_language->find_main_name->
> ada_main_name, and loses that when it is handling a shared library
> event that in turn evaluates probe arguments. That looks like a bug
> to me.
>
> Fix that by avoiding selecting a frame if one isn't set yet in
> expression evaluation, which is what switches to the frame's language
> as side effect.
>
> (There are a couple calls to get_selected_block in the file that
> should probably get a similar treatment, but I'm leaving those as is
> for now.)
>
> gdb/testsuite/ChangeLog:
> 2017-11-21 Pedro Alves <palves@redhat.com>
>
> * eval.c (evaluate_subexp_standard): Use
> get_selected_frame_if_set+get_current_frame instead of
> get_selected_frame.
> ---
> gdb/eval.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/gdb/eval.c b/gdb/eval.c
> index 14a3e05..b789982 100644
> --- a/gdb/eval.c
> +++ b/gdb/eval.c
> @@ -1319,7 +1319,6 @@ evaluate_subexp_standard (struct type *expect_type,
>
> {
> struct symbol *sym = exp->elts[pc + 1].symbol;
> - struct frame_info *frame;
>
> if (noside == EVAL_AVOID_SIDE_EFFECTS)
> return value_zero (SYMBOL_TYPE (sym), not_lval);
> @@ -1329,7 +1328,11 @@ evaluate_subexp_standard (struct type *expect_type,
> error (_("Symbol \"%s\" does not have any specific entry value"),
> SYMBOL_PRINT_NAME (sym));
>
> - frame = get_selected_frame (NULL);
> + /* Avoid get_selected_frame because that selects the frame's
> + language as side effect. */
> + frame_info *frame = get_selected_frame_if_set ();
> + if (frame == NULL)
> + frame = get_current_frame ();
> return SYMBOL_COMPUTED_OPS (sym)->read_variable_at_entry (sym, frame);
> }
>
> @@ -1381,7 +1384,14 @@ evaluate_subexp_standard (struct type *expect_type,
> + gdbarch_num_pseudo_regs (exp->gdbarch))
> val = value_zero (register_type (exp->gdbarch, regno), not_lval);
> else
> - val = value_of_register (regno, get_selected_frame (NULL));
> + {
> + /* Avoid get_selected_frame because that selects the
> + frame's language as side effect. */
> + frame_info *frame = get_selected_frame_if_set ();
> + if (frame == NULL)
> + frame = get_current_frame ();
> + val = value_of_register (regno, frame);
> + }
> if (val == NULL)
> error (_("Value of register %s not available."), name);
> else
> --
> 2.5.5
--
Sergio
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