feature/android e7025ed689d: Update Android port

[Po Lu]

branch: feature/android
commit e7025ed689dcc1640328f7a0e2039c3c4e2d45ee
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Update Android port
    
    * configure.ac:
    * m4/ndk-build.m4 (ndk_INIT):
    (ndk_LATE): Avoid AC_REQUIRE magic.
---
 configure.ac    | 5 ++---
 m4/ndk-build.m4 | 9 +++++++--
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/configure.ac b/configure.ac
index 1dfd880eaa9..44dbf60f938 100644
--- a/configure.ac
+++ b/configure.ac
@@ -165,7 +165,7 @@ fi
 AC_CANONICAL_HOST
 AC_CANONICAL_BUILD
 
-if test "$XCONFIGURE" = "android"; then
+AS_IF([test "$XCONFIGURE" = "android"],[
   # Initialize the Android NDK build system.  Make sure to use the
   # passed through NDK path.
   # Make sure to pass through the CFLAGS, as older versions of the
@@ -174,8 +174,7 @@ if test "$XCONFIGURE" = "android"; then
   with_ndk_cxx_shared="$android_ndk_cxx_shared"
   with_ndk_cxx="$android_ndk_cxx"
   ndk_INIT([$android_abi], [$ANDROID_SDK], [cross/ndk-build],
-           [$ANDROID_CFLAGS])
-fi
+           [$ANDROID_CFLAGS])])
 
 case $host in
  *-mingw*)
diff --git a/m4/ndk-build.m4 b/m4/ndk-build.m4
index 077781ec38c..9af681a08c8 100644
--- a/m4/ndk-build.m4
+++ b/m4/ndk-build.m4
@@ -38,7 +38,7 @@ AC_ARG_WITH([ndk_cxx],
 # DIR should be a directory containing the Makefile.in actually
 # implementing the Android NDK build system.
 
-AC_DEFUN_ONCE([ndk_INIT],
+AC_DEFUN([ndk_INIT],
 [
 # Look for Android.mk files.
 ndk_module_files=
@@ -347,13 +347,18 @@ AS_IF([test -n "$with_ndk_cxx"], [CXX=$with_ndk_cxx],
 # required C and C++ headers.
 
 AC_DEFUN([ndk_LATE],
-[
+[dnl
+dnl This calls AC_REQUIRE([AC_PROG_CXX]), leading to configure looking
+dnl for a C++ compiler.  However, the language is not restored
+dnl afterwards if not `$ndk_INITIALIZED'.
 AS_IF([test "$ndk_INITIALIZED" = "yes"],[
   AS_IF([test -n "$CXX"], [AC_LANG_PUSH([C++])
     AC_CHECK_HEADER([string], [ndk_working_cxx=yes],
       [AC_MSG_WARN([Your C++ compiler is not properly set up, and\
  the standard library headers could not be found.])])
     AC_LANG_POP([C++])])])
+dnl Thus, manually switch back to C here.
+AC_LANG([C])
 ])
 
 # ndk_SEARCH_MODULE(MODULE, NAME, ACTION-IF-FOUND, [ACTION-IF-NOT-FOUND])