Re: [RFA/RFC Prec] Add process record skip 6/6 (doc)

Eli Zaretskii
2009-08-31T16:47:01Z

> From: Hui Zhu <teawater@gmail.com>
> Date: Mon, 31 Aug 2009 21:26:04 +0800
> Cc: gdb-patches@sourceware.org, msnyder@vmware.com, green@moxielogic.com
>
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> On Thu, Aug 27, 2009 at 01:50, Eli Zaretskii<eliz@gnu.org> wrote:
> >> From: Hui Zhu <teawater@gmail.com>
> >> Date: Tue, 25 Aug 2009 11:47:09 +0800
> >> Cc: gdb-patches@sourceware.org, msnyder@vmware.com, green@moxielogic.com
> >>
> >> >> i386_linux_process_record_simple_function is for printf.
> >> >> i386_linux_process_record_memset is for memset and memcpy.
> >> >
> >> > So we currently support record skip of only 3 functions, the ones
> >> > mentioned above, is that right? =A0In that case, we should document
> >> > those functions in the manual, I think.
> >>
> >> Yes, I think after this feature in, we can add more and more functions
> >> to support skip.
> >
> > But then the proposed code is IMHO awfully limited, isn't it? Why
> > not add some more general mechanism, for several broad classes of
> > functions (like the `simple_function' class you used for `printf'),
> > and let the user specify which functions she wants to skip, instead of
> > hard-coding the functions in GDB?
> >
> > By contrast, the suggested code will cause us to have gobs of library
> > functions intimately known to GDB, and will bloat the executable, for
> > starters.

You didn't answer these concerns. Nor did anyone else; am I the only
one who is bothered by the ad-hoc nature of such design?

> > Also, why is this code being make Linux-specific? =A0Surely, most, if
> > not all, other implementations of `printf', `memset' and `memcpy' have
> > the exact same API and the same external effects as those you have in
> > glibc, no?
>
> The api is same, but the ABI for each arch and os is not same, each
> printf, memset or memcpy of each arch-os will get the argument from
> different memory and different register. And they will change
> different memory and reg.

Are you talking in general, or are you talking about the x86
architecture? I think all x86 implementations of `printf' and
`memset' will use the same ABI, certainly those that use GCC as the
native compiler.

> +The record skip entry is a special breakpoint. When the process
> +record and replay target start, it will be inserted to the
> +begin of a function. When this breakpoint break the inferior and
^^^^^ ^^^^^ ^^^^
"beginning" "breaks" ", if"

> +@value{GDBN} is in record mode, @value{GDBN} will skip record all
^^^^^^^^^^^^^^^
"refrain from recording"

> +the execution log of this function's instructions and record the
^^^^^^^^^^
"and only record"

> +change of memory and registers of this function as one instruction.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
"modifications of memory and registers by this function"

> +Show the status of record skip.

"This command shows the status of record skipping."

> +@item record skip disable @r{[}id@r{]}
^^
"@var{id}"

> +@item record skip enable @r{[}id@r{]}

Likewise.

OK with these changes.

Thanks.