[PATCH for-4.15] autoconf: check endian.h include path

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Introduce an autoconf macro to check for the include path of certain
headers that can be different between OSes.

Use such macro to find the correct path for the endian.h header, and
modify the users of endian.h to use the output of such check.

Suggested-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Please re-run autogen after applying.

The biggest risk for this would be some kind of configure or build
failure, and we should be able to catch it in either osstest or the
gitlab build tests.
---
 m4/header.m4                                      | 13 +++++++++++++
 tools/configure.ac                                |  3 +++
 tools/libs/guest/xg_dom_decompress_unsafe_lzo1x.c |  2 +-
 tools/libs/guest/xg_dom_decompress_unsafe_xz.c    |  2 +-
 tools/libs/guest/xg_dom_decompress_unsafe_zstd.c  |  2 +-
 tools/xenstore/include/xenstore_state.h           |  6 +-----
 6 files changed, 20 insertions(+), 8 deletions(-)
 create mode 100644 m4/header.m4

diff --git a/m4/header.m4 b/m4/header.m4
new file mode 100644
index 0000000000..81d1d65194
--- /dev/null
+++ b/m4/header.m4
@@ -0,0 +1,13 @@
+AC_DEFUN([AX_FIND_HEADER], [
+ax_found=0
+m4_foreach_w([header], $2, [
+    AS_IF([test "$ax_found" = "0"], [
+        AC_CHECK_HEADER(header, [
+            AC_DEFINE($1, [<header>], [Header path for $1])
+            ax_found=1])
+    ])
+])
+AS_IF([test "$ax_found" = "0"], [
+    AC_MSG_ERROR([No header found from list $2])
+])
+])
diff --git a/tools/configure.ac b/tools/configure.ac
index 5b328700e0..3a3e7b4b2b 100644
--- a/tools/configure.ac
+++ b/tools/configure.ac
@@ -74,6 +74,7 @@ m4_include([../m4/ax_compare_version.m4])
 m4_include([../m4/paths.m4])
 m4_include([../m4/systemd.m4])
 m4_include([../m4/golang.m4])
+m4_include([../m4/header.m4])
 
 AX_XEN_EXPAND_CONFIG()
 
@@ -517,4 +518,6 @@ AC_ARG_ENABLE([pvshim],
 ])
 AC_SUBST(pvshim)
 
+AX_FIND_HEADER([INCLUDE_ENDIAN_H], [endian.h sys/endian.h])
+
 AC_OUTPUT()
diff --git a/tools/libs/guest/xg_dom_decompress_unsafe_lzo1x.c 
b/tools/libs/guest/xg_dom_decompress_unsafe_lzo1x.c
index a4f8ebd42d..e58c1b95ed 100644
--- a/tools/libs/guest/xg_dom_decompress_unsafe_lzo1x.c
+++ b/tools/libs/guest/xg_dom_decompress_unsafe_lzo1x.c
@@ -1,7 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <inttypes.h>
-#include <endian.h>
+#include INCLUDE_ENDIAN_H
 #include <stdint.h>
 
 #include "xg_private.h"
diff --git a/tools/libs/guest/xg_dom_decompress_unsafe_xz.c 
b/tools/libs/guest/xg_dom_decompress_unsafe_xz.c
index ff6824b38d..fc48198741 100644
--- a/tools/libs/guest/xg_dom_decompress_unsafe_xz.c
+++ b/tools/libs/guest/xg_dom_decompress_unsafe_xz.c
@@ -1,5 +1,5 @@
 #include <stdio.h>
-#include <endian.h>
+#include INCLUDE_ENDIAN_H
 #include <stdlib.h>
 #include <stddef.h>
 #include <stdint.h>
diff --git a/tools/libs/guest/xg_dom_decompress_unsafe_zstd.c 
b/tools/libs/guest/xg_dom_decompress_unsafe_zstd.c
index 52558d2ffc..01eafaaaa6 100644
--- a/tools/libs/guest/xg_dom_decompress_unsafe_zstd.c
+++ b/tools/libs/guest/xg_dom_decompress_unsafe_zstd.c
@@ -1,5 +1,5 @@
 #include <stdio.h>
-#include <endian.h>
+#include INCLUDE_ENDIAN_H
 #include <stdlib.h>
 #include <stddef.h>
 #include <stdint.h>
diff --git a/tools/xenstore/include/xenstore_state.h 
b/tools/xenstore/include/xenstore_state.h
index f7e4da2b2c..ae0d053c8f 100644
--- a/tools/xenstore/include/xenstore_state.h
+++ b/tools/xenstore/include/xenstore_state.h
@@ -21,11 +21,7 @@
 #ifndef XENSTORE_STATE_H
 #define XENSTORE_STATE_H
 
-#if defined(__FreeBSD__) || defined(__NetBSD__)
-#include <sys/endian.h>
-#else
-#include <endian.h>
-#endif
+#include INCLUDE_ENDIAN_H
 #include <sys/types.h>
 
 #ifndef htobe32
-- 
2.29.2