Merge branch '909-add-explicit-link-check-for-libatomic' into 'master'

Add explicit check for libatomic to fix configure step on NetBSD

Closes #909

See merge request isc-projects/bind9!1586

PLATFORMS.md

@@ -95,8 +95,18 @@ armhf documentation):
   the processors to support here, therefore the recommended build option is
   `-mfpu=vfpv3-d16`.
 
-The configure command should look like this:
+The `configure` command should look like this:
 
 ```
 CFLAGS="-march=armv7-a -mfpu=vfpv3-d16 -Os -g" ./configure
 ```
+
+### NetBSD 6 i386
+
+The i386 build of NetBSD requires the `libatomic` library, available from
+the `gcc5-libs` package.  Because this library is in a non-standard path,
+its location must be specified in the `configure` command line:
+
+```
+LDFLAGS="-L/usr/pkg/gcc5/i486--netbsdelf/lib/ -Wl,-R/usr/pkg/gcc5/i486--netbsdelf/lib/" ./configure
+```

configure

@@ -17958,9 +17958,33 @@ if ac_fn_c_try_link "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
 else
+  ISC_ATOMIC_LIBS="-latomic"
+	 save_LIBS="$LIBS"
+	 LIBS="$LIBS $ISC_ATOMIC_LIBS"
+	 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <stdatomic.h>
+int
+main ()
+{
+atomic_int_fast64_t val = 0; atomic_fetch_add_explicit(&val, 1, memory_order_relaxed);
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 $as_echo "yes" >&6; }
-	 ISC_ATOMIC_LIBS="-latomic"
+else
+  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "libatomic needed, but linking with -latomic failed, please fix your toolchain.
+See \`config.log' for more details" "$LINENO" 5; }
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+	 LIBS="$save_LIBS"
 
 fi
 rm -f core conftest.err conftest.$ac_objext \
@@ -17969,7 +17993,7 @@ rm -f core conftest.err conftest.$ac_objext \
 else
   { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-as_fn_error $? "stdatomic.h header found, but compilation failed, fix your toolchaing.
+as_fn_error $? "stdatomic.h header found, but compilation failed, please fix your toolchain.
 See \`config.log' for more details" "$LINENO" 5; }
 
 fi
@@ -18013,9 +18037,33 @@ if ac_fn_c_try_link "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
 else
+  ISC_ATOMIC_LIBS="-latomic"
+	 save_LIBS="$LIBS"
+	 LIBS="$LIBS $ISC_ATOMIC_LIBS"
+	 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <inttypes.h>
+int
+main ()
+{
+int64_t val = 0; __atomic_fetch_add(&val, 1, __ATOMIC_RELAXED);
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 $as_echo "yes" >&6; }
-	 ISC_ATOMIC_LIBS="-latomic"
+else
+  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "libatomic needed, but linking with -latomic failed, please fix your toolchain.
+See \`config.log' for more details" "$LINENO" 5; }
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+	 LIBS="$save_LIBS"
 
 fi
 rm -f core conftest.err conftest.$ac_objext \

configure.ac

@@ -1939,11 +1939,20 @@ AC_CHECK_HEADERS(
 	   [[atomic_int_fast64_t val = 0; atomic_fetch_add_explicit(&val, 1, memory_order_relaxed);]]
 	 )],
 	[AC_MSG_RESULT([no])],
-	[AC_MSG_RESULT([yes])
+	[ISC_ATOMIC_LIBS="-latomic"
-	 ISC_ATOMIC_LIBS="-latomic"
+	 save_LIBS="$LIBS"
+	 LIBS="$LIBS $ISC_ATOMIC_LIBS"
+	 AC_LINK_IFELSE(
+	   [AC_LANG_PROGRAM(
+	      [[#include <stdatomic.h>]],
+	      [[atomic_int_fast64_t val = 0; atomic_fetch_add_explicit(&val, 1, memory_order_relaxed);]]
+	    )],
+	   [AC_MSG_RESULT([yes])],
+	   [AC_MSG_FAILURE([libatomic needed, but linking with -latomic failed, please fix your toolchain.])])
+	 LIBS="$save_LIBS"
 	])
      ],
-     [AC_MSG_FAILURE([stdatomic.h header found, but compilation failed, fix your toolchaing.])]
+     [AC_MSG_FAILURE([stdatomic.h header found, but compilation failed, please fix your toolchain.])]
    )],
   [AC_MSG_CHECKING([for memory model aware atomic operations])
    AC_COMPILE_IFELSE(
@@ -1960,8 +1969,17 @@ AC_CHECK_HEADERS(
 	   [[int64_t val = 0; __atomic_fetch_add(&val, 1, __ATOMIC_RELAXED);]]
 	 )],
 	[AC_MSG_RESULT([no])],
-	[AC_MSG_RESULT([yes])
+	[ISC_ATOMIC_LIBS="-latomic"
-	 ISC_ATOMIC_LIBS="-latomic"
+	 save_LIBS="$LIBS"
+	 LIBS="$LIBS $ISC_ATOMIC_LIBS"
+	 AC_LINK_IFELSE(
+	   [AC_LANG_PROGRAM(
+	      [[#include <inttypes.h>]],
+	      [[int64_t val = 0; __atomic_fetch_add(&val, 1, __ATOMIC_RELAXED);]]
+	    )],
+	   [AC_MSG_RESULT([yes])],
+	   [AC_MSG_FAILURE([libatomic needed, but linking with -latomic failed, please fix your toolchain.])])
+	 LIBS="$save_LIBS"
 	])
      ],
      [AC_MSG_RESULT([__sync builtins])