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Re: [PATCH][PR symtab/17855] Fix.
- From: Pedro Alves <palves at redhat dot com>
- To: Doug Evans <xdje42 at gmail dot com>, gdb-patches at sourceware dot org, brobecker at adacore dot com
- Date: Thu, 22 Jan 2015 11:41:51 +0000
- Subject: Re: [PATCH][PR symtab/17855] Fix.
- Authentication-results: sourceware.org; auth=none
- References: <m33876ary6 dot fsf at sspiff dot org>
On 01/20/2015 06:26 AM, Doug Evans wrote:
> Hi.
>
> This patch fixes symtab/17855.
> Basically the issue is that breakpoint_re_set is currently being called
> before observer_notify_new_objfile (NULL), and thus the ada symbol
> cache (and the general symbol cache of a separate patch) aren't being
> flushed first, so that when breakpoints are reset symbol lookup is being
> done on a stale cache.
>
> Regression tested on amd64-linux.
>
> 2015-01-19 Doug Evans <xdje42@gmail.com>
>
> PR symtab/17855
> * symfile.c (clear_symtab_users): Notify observers of change before
> calling breakpoint_re_set.
>
> diff --git a/gdb/symfile.c b/gdb/symfile.c
> index d55e361..ad481de 100644
> --- a/gdb/symfile.c
> +++ b/gdb/symfile.c
> @@ -3023,6 +3023,12 @@ clear_symtab_users (int add_flags)
> /* Someday, we should do better than this, by only blowing away
> the things that really need to be blown. */
>
> + /* Notify anyone listening that the previous loaded symtab(s) are invalid.
> + It is important to do this before calling breakpoint_re_set as the latter
> + will try to look up symbols, and for example the symbol cache needs to
> + be flushed first. */
> + observer_notify_new_objfile (NULL);
> +
> /* Clear the "current" symtab first, because it is no longer valid.
> breakpoint_re_set may try to access the current symtab. */
> clear_current_source_symtab_and_line ();
> @@ -3032,7 +3038,6 @@ clear_symtab_users (int add_flags)
> breakpoint_re_set ();
> clear_last_displayed_sal ();
> clear_pc_function_cache ();
> - observer_notify_new_objfile (NULL);
Looking at the whole function, ISTM that the breakpoint_re_set
call should move further down. I can imagine that breakpoint_re_set
could well hit a stale pc function cache, cleared only after by
clear_pc_function_cache. breakpoint.c:parse_breakpoint_sals also
references the last displayed sal. One would hope that breakpoint
re-set is independent of that, though the existing comment about
breakpoint_re_set accessing the current symtab leaves me
wondering. WDYT?
Thanks,
Pedro Alves