From 598fe5e69ed0eba9eabf0745940caab2852ec53b Mon Sep 17 00:00:00 2001
From: Moritz Bunkus <moritz@bunkus.org>
Date: Sat, 25 May 2019 17:48:24 +0200
Subject: [PATCH] configure: fix detection of libebml::FindNextChild

The internal libEBML was updated to v1.3.9. That version contains
changes to cmake to build an additional header file, ebml_export.h. In
MKVToolNix, which isn't cmake-based, that file has to be created
manually, and the Rakefile does so.

However, when configure runs the file doesn't exist yet. This means
that any attempt to compile a test program with the internal libebml
will fail due to the header not being found. configure's compilation
checks will therefore fail.

For the detection of libebml::FindNextChild doing a compilation check
against the internal libebml isn't really needed as we know that the
version does include it. So just hardcode that knowledge and avoid the
compilation check.
---
 ac/matroska.m4 | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/ac/matroska.m4 b/ac/matroska.m4
index b5e1634f3..fef8dbf3c 100644
--- a/ac/matroska.m4
+++ b/ac/matroska.m4
@@ -32,34 +32,33 @@ fi
 
 AC_DEFUN([AX_EBML_FINDNEXTCHILD],[
   AC_CACHE_CHECK([if libEBML contains FindNextChild], [ax_cv_ebml_findnextchild],[
-    CXXFLAGS_SAVED=$CXXFLAGS
-
     if test x"$EBML_MATROSKA_INTERNAL" = xyes; then
-      CXXFLAGS="-Ilib/libebml -Ilib/libmatroska"
+      ax_cv_ebml_findnextchild=yes
     else
+      CXXFLAGS_SAVED=$CXXFLAGS
       CXXFLAGS="$EBML_CFLAGS $MATROSKA_CFLAGS"
-    fi
-    export CXXFLAGS
+      export CXXFLAGS
 
-    AC_LANG_PUSH(C++)
-    AC_TRY_COMPILE(
-      [
+      AC_LANG_PUSH(C++)
+      AC_TRY_COMPILE(
+        [
 #include <matroska/KaxInfo.h>
 #include <matroska/KaxSegment.h>
 
 using namespace libebml;
 using namespace libmatroska;
-      ],
-      [
+        ],
+        [
   EbmlMaster *m = new KaxSegment;
   EbmlElement *e = new KaxTitle;
   FindNextChild(*m, *e);
-  ],
-      [ax_cv_ebml_findnextchild="yes"],
-      [ax_cv_ebml_findnextchild="no"])
-    AC_LANG_POP
+    ],
+        [ax_cv_ebml_findnextchild="yes"],
+        [ax_cv_ebml_findnextchild="no"])
+      AC_LANG_POP
 
-    CXXFLAGS="$CXXFLAGS_SAVED"
+      CXXFLAGS="$CXXFLAGS_SAVED"
+    fi
   ])
 
   if test x"$ax_cv_ebml_findnextchild" = xyes; then