[Spice-devel] [common 01/11] build-sys: Add the SPICE_WARNING() and SPICE_PRINT_MESSAGES m4 macros

[Francois Gouget]

A call to SPICE_WARNING() anywhere in the configure file results in the
warning being printed at the end of the configure run where it will be
be visible. This makes it possible to keep the SPICE_WARNING() calls
together with the related feature checks instead of having to put a
separate AC_MSG_WARN() call near the end.

Signed-off-by: Francois Gouget <fgouget at codeweavers.com>
---
 m4/spice-deps.m4 | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

For reference, see also:
http://lists.freedesktop.org/archives/spice-devel/2015-November/023009.html

diff --git a/m4/spice-deps.m4 b/m4/spice-deps.m4
index 0f90cec..57d5b78 100644
--- a/m4/spice-deps.m4
+++ b/m4/spice-deps.m4
@@ -1,3 +1,24 @@
+# For autoconf < 2.63
+m4_ifndef([AS_VAR_APPEND],
+          AC_DEFUN([AS_VAR_APPEND], $1=$$1$2))
+
+# SPICE_WARNING(warning)
+# SPICE_PRINT_MESSAGES
+# ----------------------
+# Collect warnings and print them at the end so they are clearly visible.
+# ---------------------
+AC_DEFUN([SPICE_WARNING],AS_VAR_APPEND([spice_warnings],["|$1"]))
+AC_DEFUN([SPICE_PRINT_MESSAGES],[
+    ac_save_IFS="$IFS"
+    IFS="|"
+    for msg in $spice_warnings; do
+        IFS="$ac_save_IFS"
+        AS_VAR_IF([msg],[],,[AC_MSG_WARN([$msg]); echo >&2])
+    done
+    IFS="$ac_save_IFS"
+])
+
+
 # SPICE_CHECK_SYSDEPS()
 # ---------------------
 # Checks for header files and library functions needed by spice-common.
-- 
2.6.1