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

[Thiago Jung Bauermann <thiago dot bauermann at linaro dot org>]

Hello Joel,

On Tue, 2012-03-27 at 08:20 -0700, Joel Brobecker wrote:
> > 2012-03-26  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.
> 
> (you'll need to mention the fact that configure and config.in need
> to be regenerated)

Oops, I forgot. Fixed.

> I am not very familiar with this area, so I am hoping someone else
> might provide feedback as well.

Thanks for your review!

> > 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.

> (let's wait for more feedback before we make any change - someone
> might disagree)

It's an easy change so I did it anyway. Here's the new version.
-- 
[]'s
Thiago Jung Bauermann
Linaro Toolchain Working Group


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.


diff --git a/gdb/gdbserver/configure.ac b/gdb/gdbserver/configure.ac
index e6e9162..5d1e094 100644
--- a/gdb/gdbserver/configure.ac
+++ b/gdb/gdbserver/configure.ac
@@ -168,6 +168,10 @@ AC_CHECK_TYPES(socklen_t, [], [],
 #include <sys/socket.h>
 ])
 
+AC_CHECK_TYPES([Elf32_auxv_t, Elf64_auxv_t], [], [],
+#include <elf.h>
+)
+
 ACX_PKGVERSION([GDB])
 ACX_BUGURL([http://www.gnu.org/software/gdb/bugs/])
 AC_DEFINE_UNQUOTED([PKGVERSION], ["$PKGVERSION"], [Additional package description])
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 8becf78..1caff5a 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -82,6 +82,34 @@
 #endif
 #endif
 
+#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
+
+#ifndef HAVE_ELF64_AUXV_T
+typedef struct
+{
+  uint64_t a_type;		/* Entry type */
+  union
+    {
+      uint64_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;
+} Elf64_auxv_t;
+#endif
+
 /* ``all_threads'' is keyed by the LWP ID, which we use as the GDB protocol
    representation of the thread ID.