wscript: 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

@@ -104,20 +104,20 @@ 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__) && !defined(nios2)
+#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)

wscript

@@ -496,6 +496,21 @@ def configure(conf):
 
     conf.recurse('example-clients')
 
+    # 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.env['LIB_PTHREAD'] = ['pthread']
     conf.env['LIB_DL'] = ['dl']
     conf.env['LIB_RT'] = ['rt']