[gobject-introspection/warn-flags] build: enable -Wdouble-promotion

[Christoph Reiter <creiter src gnome org>]

commit 666dfabfdabd8fb802f84004d9cb6cf1ab4598da
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Sun Jul 29 14:54:34 2018 +0200

    build: enable -Wdouble-promotion

 configure.ac             | 2 +-
 girepository/girwriter.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 6898741a..91a56251 100644
--- a/configure.ac
+++ b/configure.ac
@@ -66,7 +66,7 @@ AX_COMPILER_FLAGS(,, [yes])
 AX_APPEND_COMPILE_FLAGS([-Wno-switch-enum])
 # FIXME: Fix the warnings and remove the flags
 AX_APPEND_COMPILE_FLAGS([-Wno-redundant-decls -Wno-switch-default -Wno-shadow -Wno-deprecated-declarations 
-Wno-cast-function-type -Wno-type-limits])
-AX_APPEND_COMPILE_FLAGS([-Wno-duplicated-branches -Wno-implicit-fallthrough -Wno-suggest-attribute=format 
-Wno-double-promotion -Wno-sign-compare])
+AX_APPEND_COMPILE_FLAGS([-Wno-duplicated-branches -Wno-implicit-fallthrough -Wno-suggest-attribute=format 
-Wno-sign-compare])
 AX_APPEND_COMPILE_FLAGS([-Wno-old-style-definition -Wno-strict-prototypes])
 
 WARN_CFLAGS_PYTHON="$WARN_CFLAGS"
diff --git a/girepository/girwriter.c b/girepository/girwriter.c
index dacce86f..1b61de03 100644
--- a/girepository/girwriter.c
+++ b/girepository/girwriter.c
@@ -748,7 +748,7 @@ write_constant_value (const gchar *namespace,
       xml_printf (file, "%" G_GUINT64_FORMAT, value->v_uint64);
       break;
     case GI_TYPE_TAG_FLOAT:
-      xml_printf (file, "%f", value->v_float);
+      xml_printf (file, "%f", (double)value->v_float);
       break;
     case GI_TYPE_TAG_DOUBLE:
       xml_printf (file, "%f", value->v_double);