[Unbound-users] [PATCH] acx_nlnetlabs.m4: ACX_CHECK_LTO: add --disable-flto configure option

[edmonds at debian.org]

From: Robert Edmonds <edmonds at isc.org>

This allows link-time optimization to be disabled if --disable-flto is
passed to configure. This might be useful if LTO is broken on the build
architecture, or to speed up the build during development.
---
 acx_nlnetlabs.m4 | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/acx_nlnetlabs.m4 b/acx_nlnetlabs.m4
index e393817..c288c35 100644
--- a/acx_nlnetlabs.m4
+++ b/acx_nlnetlabs.m4
@@ -407,19 +407,22 @@ int test() {
 dnl Check if CC supports -flto.
 dnl in a way that supports clang and suncc (that flag does something else,
 dnl but fails to link).  It sets it in CFLAGS if it works.
-AC_DEFUN([ACX_CHECK_FLTO],
-[AC_MSG_CHECKING([if $CC supports -flto])
-BAKCFLAGS="$CFLAGS"
-CFLAGS="$CFLAGS -flto"
-AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])], [
-    if $CC $CFLAGS -o conftest conftest.c 2>&1 | grep "warning: no debug symbols in executable" >/dev/null; then
-	CFLAGS="$BAKCFLAGS"
-	AC_MSG_RESULT(no)
-    else
-	AC_MSG_RESULT(yes)
-    fi
-    rm -f conftest conftest.c conftest.o
-], [CFLAGS="$BAKCFLAGS" ; AC_MSG_RESULT(no)])
+AC_DEFUN([ACX_CHECK_FLTO], [
+    AC_ARG_ENABLE([flto], AS_HELP_STRING([--disable-flto], [Disable link-time optimization]))
+    AS_IF([test "x$enable_flto" != "xno"], [
+        AC_MSG_CHECKING([if $CC supports -flto])
+        BAKCFLAGS="$CFLAGS"
+        CFLAGS="$CFLAGS -flto"
+        AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])], [
+            if $CC $CFLAGS -o conftest conftest.c 2>&1 | grep "warning: no debug symbols in executable" >/dev/null; then
+                CFLAGS="$BAKCFLAGS"
+                AC_MSG_RESULT(no)
+            else
+                AC_MSG_RESULT(yes)
+            fi
+            rm -f conftest conftest.c conftest.o
+        ], [CFLAGS="$BAKCFLAGS" ; AC_MSG_RESULT(no)])
+    ])
 ])
 
 dnl Check the printf-format attribute (if any)
-- 
1.8.3.rc1