Merge branch '612-problems-compiling-on-arm-processor' into 'master'

Resolve "Problems compiling on arm processor"

Closes #612

See merge request isc-projects/bind9!869

PLATFORMS.md

@@ -67,3 +67,34 @@ These are platforms on which BIND is known *not* to build or run:
 * Platforms that don't support IPv6 Advanced Socket API (RFC 3542)
 * Platforms that don't support atomic operations (via compiler or library)
 * Linux without NPTL (Native POSIX Thread Library)
+
+## Platform quirks
+
+### ARM
+
+If the compilation ends with following error:
+
+```
+Error: selected processor does not support `yield' in ARM mode
+```
+
+You will need to set `-march` compiler option to `native`, so the compiler
+recognizes `yield` assembler instruction.  The proper way to set `-march=native`
+would be to put it into `CFLAGS`, e.g. run `./configure` like this:
+`CFLAGS="-march=native -Os -g" ./configure` plus your usual options.
+
+If that doesn't work, you can enforce the minimum CPU and FPU (taken from Debian
+armhf documentation):
+
+* The lowest worthwhile CPU implementation is Armv7-A, therefore the recommended
+  build option is `-march=armv7-a`.
+
+* FPU should be set at VFPv3-D16 as they represent the miminum specification of
+  the processors to support here, therefore the recommended build option is
+  `-mfpu=vfpv3-d16`.
+
+The configure command should look like this:
+
+```
+CFLAGS="-march=armv7-a -mfpu=vfpv3-d16 -Os -g" ./configure
+```

configure

@@ -13618,6 +13618,37 @@ $as_echo "#define FLEXIBLE_ARRAY_MEMBER /**/" >>confdefs.h
   fi
 
 
+#
+# Check for yield support on ARM processors
+#
+case $host in #(
+  arm*) :
+
+	  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for yield instruction support" >&5
+$as_echo_n "checking for yield instruction support... " >&6; }
+	  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+__asm__ __volatile__ ("yield")
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+else
+  as_fn_error $? "no, try adding -march=native or -march=armv7-a to CFLAGS (see PLATFORM.md for more information)" "$LINENO" 5
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext ;; #(
+  *) :
+     ;;
+esac
+
 for ac_func in sysctlbyname
 do :
   ac_fn_c_check_func "$LINENO" "sysctlbyname" "ac_cv_func_sysctlbyname"

configure.in

@@ -460,6 +460,20 @@ AC_C_INLINE
 AC_C_VOLATILE
 AC_C_FLEXIBLE_ARRAY_MEMBER
 
+#
+# Check for yield support on ARM processors
+#
+AS_CASE([$host],
+	[arm*],[
+	  AC_MSG_CHECKING([for yield instruction support])
+	  AC_COMPILE_IFELSE(
+	    [AC_LANG_PROGRAM(
+	       [[]],
+	       [[__asm__ __volatile__ ("yield")]]
+	     )],
+	    [AC_MSG_RESULT([yes])],
+	    [AC_MSG_ERROR([no, try adding -march=native or -march=armv7-a to CFLAGS (see PLATFORM.md for more information)])])])
+
 AC_CHECK_FUNCS([sysctlbyname])
 
 #

lib/isc/rwlock.c

@@ -52,7 +52,7 @@
 #elif defined(__arm__)
 # define isc_rwlock_pause() __asm__ __volatile__ ("yield")
 #elif defined(__sparc) || defined(__sparc__)
-# define plasma_spin_pause() __asm__ __volatile__ ("pause")
+# define isc_rwlock_pause() __asm__ __volatile__ ("pause")
 #elif defined(__ppc__) || defined(_ARCH_PPC)  ||			\
 	defined(_ARCH_PWR) || defined(_ARCH_PWR2) || defined(_POWER)
 # define isc_rwlock_pause() __asm__ volatile ("or 27,27,27")