From ad79670d6d1e7ef2aad6935715921e5317cbe618 Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Date: Mon, 23 May 2016 22:28:12 +0200
Subject: [PATCH] Improve check for ucontext

The ucontext functionality is not available on all CPUs with all C
libraries. Instead of making just assumptions based on the CPU
architecture, this commit adds the necessary checks in wscript to verify
the availability of the ucontext functionality, before using it in
dbus/sigsegv.c.

This avoids the long list of architecture exclusions, and make it more
robust when building jack2 for new CPU architectures.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
 dbus/sigsegv.c | 12 ++++++------
 wscript        | 16 +++++++++++++++-
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/dbus/sigsegv.c b/dbus/sigsegv.c
index df2c42c..00a62b5 100644
--- a/dbus/sigsegv.c
+++ b/dbus/sigsegv.c
@@ -106,20 +106,20 @@ static void signal_segv(int signum, siginfo_t* info, void*ptr) {
     jack_error("info.si_errno = %d", info->si_errno);
     jack_error("info.si_code  = %d (%s)", info->si_code, si_code_str);
     jack_error("info.si_addr  = %p", info->si_addr);
-#if !defined(__alpha__) && !defined(__ia64__) && !defined(__FreeBSD_kernel__) && !defined(__arm__) && !defined(__hppa__) && !defined(__sh__) && !defined(__aarch64__)
+#if defined(HAVE_UCONTEXT) && defined(HAVE_NGREG)
     for(i = 0; i < NGREG; i++)
         jack_error("reg[%02d]       = 0x" REGFORMAT, i, 
-#if defined(__powerpc64__)
+#if defined(HAVE_UCONTEXT_GP_REGS)
                 ucontext->uc_mcontext.gp_regs[i]
-#elif defined(__powerpc__)
+#elif defined(HAVE_UCONTEXT_UC_REGS)
                 ucontext->uc_mcontext.uc_regs[i]
-#elif defined(__sparc__) && defined(__arch64__)
+#elif defined(HAVE_UCONTEXT_MC_GREGS)
                 ucontext->uc_mcontext.mc_gregs[i]
-#else
+#elif defined(HAVE_UCONTEXT_GREGS)
                 ucontext->uc_mcontext.gregs[i]
 #endif
                 );
-#endif /* alpha, ia64, kFreeBSD, arm, hppa */
+#endif /* defined(HAVE_UCONTEXT) && defined(HAVE_NGREG) */
 
 #if defined(SIGSEGV_STACK_X86) || defined(SIGSEGV_STACK_IA64)
 # if defined(SIGSEGV_STACK_IA64)
diff --git a/wscript b/wscript
index 63ba3aa..34a56fc 100644
--- a/wscript
+++ b/wscript
@@ -168,10 +168,24 @@ def configure(conf):
 
     conf.check_cc(header_name='execinfo.h', define_name="HAVE_EXECINFO_H", mandatory=False)
     conf.check_cc(header_name='samplerate.h', define_name="HAVE_SAMPLERATE")
-
     if conf.is_defined('HAVE_SAMPLERATE'):
         conf.env['LIB_SAMPLERATE'] = ['samplerate']
 
+    # test for the availability of ucontext, and how it should be used
+    for t in ("gp_regs", "uc_regs", "mc_gregs", "gregs"):
+        fragment = "#include <ucontext.h>\n"
+        fragment += "int main() { ucontext_t *ucontext; return (int) ucontext->uc_mcontext.%s[0]; }" % t
+        confvar = "HAVE_UCONTEXT_%s" % t.upper()
+        conf.check_cc(fragment=fragment, define_name=confvar, mandatory=False,
+                      msg="Checking for ucontext->uc_mcontext.%s" % t)
+        if conf.is_defined(confvar):
+            conf.define('HAVE_UCONTEXT', 1)
+
+    fragment = "#include <ucontext.h>\n"
+    fragment += "int main() { return NGREG; }"
+    conf.check_cc(fragment=fragment, define_name="HAVE_NGREG", mandatory=False,
+                  msg="Checking for NGREG")
+
     conf.sub_config('example-clients')
 
     if conf.check_cfg(package='celt', atleast_version='0.11.0', args='--cflags --libs', mandatory=False):
-- 
2.7.4