Re: [RFA] Define Elf32_auxv_t and Elf64_auxv_t if not available.

Pedro Alves
2012-03-29T16:03:15Z

Hello Thiago,

On 03/28/2012 01:11 AM, Thiago Jung Bauermann wrote:

> On Tue, 2012-03-27 at 08:20 -0700, Joel Brobecker wrote:
>>> > > 2012-03-26 Thiago Jung Bauermann <thiago.bauermann@linaro.org>

>>> > > diff --git a/gdb/gdbserver/configure.ac b/gdb/gdbserver/configure.ac
>>> > > index e6e9162..6b98dc0 100644
>>> > > --- a/gdb/gdbserver/configure.ac
>>> > > +++ b/gdb/gdbserver/configure.ac
>>> > > @@ -163,9 +163,10 @@ fi
>>> > >
>>> > > AC_CHECK_DECLS([strerror, perror, memmem, vasprintf, vsnprintf])
>>> > >
>>> > > -AC_CHECK_TYPES(socklen_t, [], [],
>>> > > +AC_CHECK_TYPES([socklen_t, Elf32_auxv_t, Elf64_auxv_t], [], [],
>>> > > [#include <sys/types.h>
>>> > > #include <sys/socket.h>
>>> > > +#include <elf.h>
>>> > > ])
>> >
>> > I wonder if we shouldn't be using two separate checks here. Seems
>> > unlikely to be a problem in practice, but we're looking for for
>> > a type is <sys/types.h> + <sys/socket.h>, and then looking for another
>> > collection of types in <elf.h>. We know we're most likely not going
>> > to get any "cross-polination" finding socklen_t in <elf.h>, but if
>> > this sort of thing were to happen, we would be in a situation where
>> > the configure check finds the type, but the code (which presumably
>> > might only include types.h and sockets.h) does not, leading to a build
>> > error.
> That's a good point, I didn't think of that. Like you say it's unlikely
> to happen in practice but it's cleaner indeed.

Separate tests is definitely the way to go, but for the reason that you'd
be always breaking the socklen_t test on non-elf ports, such
as the Windows port, where elf.h doesn't even exist.

> 2012-03-27 Thiago Jung Bauermann <thiago.bauermann@linaro.org>
>
> * configure.ac: Check whether Elf32_auxv_t and Elf64_auxv_t
> are available.
> linux-low.c [HAVE_ELF32_AUXV_T] (Elf32_auxv_t): Add typedef.
> [HAVE_ELF64_AUXV_T] (Elf64_auxv_t): Likewise.
> * config.in: Regenerate.
> * configure: Likewise.

This version looks good to me.

A "Copied from glibc's elf.h." small comment here would be good,
I think. Otherwise, the "We use to have pointer elements added here"
comment is misleading. :-)

> +#ifndef HAVE_ELF32_AUXV_T
> +typedef struct
> +{
> + uint32_t a_type; /* Entry type */
> + union
> + {
> + uint32_t a_val; /* Integer value */
> + /* We use to have pointer elements added here. We cannot do that,
> + though, since it does not work when using 32-bit definitions
> + on 64-bit platforms and vice versa. */
> + } a_un;
> +} Elf32_auxv_t;
> +#endif
> +

--
Pedro Alves