xserver_xorg-server: fix libunwind on MIPS with 32-bit pointers

Adding a patch to fix a compilation problem of Xorg + libunwind support
when building it on MIPS variants with 32-bit pointers.

Related:

  http://lists.busybox.net/pipermail/buildroot/2014-December/114404.html

Patch submitted upstream:

  http://lists.x.org/archives/xorg-devel/2015-January/045226.html

Patch reviewed by an Xorg developer:

  http://lists.x.org/archives/xorg-devel/2015-January/045383.html

Fixes:

  http://autobuild.buildroot.net/results/87b/87be2c95957f9925c1258812e536df72689fc5da/

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/x11r7/xserver_xorg-server/0004-backtrace.c-Fix-word-cast-to-a-pointer.patch

@@ -0,0 +1,90 @@
+backtrace.c: Fix word cast to a pointer
+
+This patch fixes a compilation problem of Xorg + libunwind support when
+building it on MIPS variants with 32-bit pointers.
+
+Related:
+
+  http://lists.busybox.net/pipermail/buildroot/2014-December/114404.html
+
+Patch submitted upstream:
+
+  http://lists.x.org/archives/xorg-devel/2015-January/045226.html
+
+Patch reviewed by an Xorg developer:
+
+  http://lists.x.org/archives/xorg-devel/2015-January/045383.html
+
+Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
+
+From 84f04e0274661401a91efd4e9b21dccc1396e1d6 Mon Sep 17 00:00:00 2001
+From: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
+Date: Wed, 3 Dec 2014 11:34:47 +0000
+Subject: [PATCH] backtrace.c: Fix word cast to a pointer
+
+backtrace.c uses a word size provided by libunwind. In some
+architectures like MIPS, libunwind makes that word size 64-bit for all
+variants of the architecture.
+
+In the lines #90 and #98, backtrace.c tries to do a cast to a pointer,
+which fails in all MIPS variants with 32-bit pointers, like MIPS32 or
+MIPS64 n32, because it's trying to do a cast from a 64-bit wide variable
+to a 32-bit pointer:
+
+Making all in os
+make[2]: Entering directory
+`/home/test/test/1/output/build/xserver_xorg-server-1.15.1/os'
+  CC     WaitFor.lo
+  CC     access.lo
+  CC     auth.lo
+  CC     backtrace.lo
+backtrace.c: In function 'xorg_backtrace':
+backtrace.c:90:20: error: cast to pointer from integer of different size
+[-Werror=int-to-pointer-cast]
+	 if (dladdr((void *)(pip.start_ip + off), &dlinfo) &&
+dlinfo.dli_fname &&
+		    ^
+backtrace.c:98:13: error: cast to pointer from integer of different size
+[-Werror=int-to-pointer-cast]
+	     (void *)(pip.start_ip + off));
+	     ^
+cc1: some warnings being treated as errors
+make[2]: *** [backtrace.lo] Error 1
+make[2]: *** Waiting for unfinished jobs....
+
+Making the cast to a pointer-sized integer, and then to a pointer fixes
+the problem.
+
+Related:
+  https://bugs.freedesktop.org/show_bug.cgi?id=79939
+
+Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
+---
+ os/backtrace.c |    4 ++--
+ 1 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/os/backtrace.c b/os/backtrace.c
+index 3d1195b..fd129ef 100644
+--- a/os/backtrace.c
++++ b/os/backtrace.c
+@@ -87,7 +87,7 @@ xorg_backtrace(void)
+             procname[1] = 0;
+         }
+ 
+-        if (dladdr((void *)(pip.start_ip + off), &dlinfo) && dlinfo.dli_fname &&
++        if (dladdr((void *)(uintptr_t)(pip.start_ip + off), &dlinfo) && dlinfo.dli_fname &&
+                 *dlinfo.dli_fname)
+             filename = dlinfo.dli_fname;
+         else
+@@ -95,7 +95,7 @@ xorg_backtrace(void)
+ 
+         ErrorFSigSafe("%u: %s (%s%s+0x%x) [%p]\n", i++, filename, procname,
+             ret == -UNW_ENOMEM ? "..." : "", (int)off,
+-            (void *)(pip.start_ip + off));
++            (void *)(uintptr_t)(pip.start_ip + off));
+ 
+         ret = unw_step(&cursor);
+         if (ret < 0)
+-- 
+1.7.1
+