emacs/m4/ndk-build.m4

dnl Copyright (C) 2023-2024 Free Software Foundation, Inc.
dnl This file is part of GNU Emacs.

dnl GNU Emacs is free software: you can redistribute it and/or modify
dnl it under the terms of the GNU General Public License as published by
dnl the Free Software Foundation, either version 3 of the License, or
dnl (at your option) any later version.

dnl GNU Emacs is distributed in the hope that it will be useful,
dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
dnl GNU General Public License for more details.

dnl You should have received a copy of the GNU General Public License
dnl along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

# Support for building Emacs with dependencies using the Android NDK
# build system.

AC_ARG_WITH([ndk_path],
  [AS_HELP_STRING([--with-ndk-path],
    [find Android libraries in these directories])])

AC_ARG_WITH([ndk_cxx],
  [AS_HELP_STRING([--with-ndk-cxx],
    [name of the C++ compiler included with the NDK])])

# ndk_INIT(ABI, API, DIR, CFLAGS)
# -------------------------------
# Initialize the Android NDK.  ABI is the ABI being built for.
# API is the API version being built for.
# CFLAGS is a list of compiler flags.
# As a side effect, set the variable ndk_INITIALIZED to true.
# DIR should be a directory containing the Makefile.in actually
# implementing the Android NDK build system.

AC_DEFUN([ndk_INIT],
[
# Look for Android.mk files.
ndk_module_files=
for file in $with_ndk_path; do
  if test -f $file/Android.mk; then
    ndk_module_files="$ndk_module_files$file/Android.mk "
  fi
done

AC_REQUIRE_AUX_FILE([ndk-build-helper.mk])
ndk_AUX_DIR=$ac_aux_dir
ndk_ABI=$1
ndk_MODULES=
ndk_MAKEFILES=
ndk_INITIALIZED=yes
ndk_API=$2
ndk_DIR=$3
ndk_ANY_CXX=
ndk_BUILD_CFLAGS="$4"
ndk_working_cxx=no
ndk_CXX_SHARED=

AS_CASE(["$ndk_ABI"],
  [*arm64*], [ndk_ARCH=arm64],
  [*arm*], [ndk_ARCH=arm],
  [*x86_64*], [ndk_ARCH=x86_64],
  [*x86*], [ndk_ARCH=x86],
  [*mips64*], [ndk_ARCH=mips64],
  [*mips*], [ndk_ARCH=mips],
  [AC_MSG_ERROR([Failed to determine Android device architecture])])

# This is a map between pkg-config style package names and Android
# ones.

ndk_package_map="libwebpdemux:webpdemux libxml-2.0:libxml2"
ndk_package_map="$ndk_package_map sqlite3:libsqlite_static_minimal"
ndk_package_map="$ndk_package_map MagickWand:libmagickwand-7 lcms2:liblcms2"

# Replace ndk_module with the appropriate Android module name if it is
# found in ndk_package_map.

ndk_replace_pkg_config_package () {
  for ndk_stuff in $ndk_package_map; do
    ndk_key=`AS_ECHO([$ndk_stuff]) | cut -d: -f1`
    ndk_value=`AS_ECHO([$ndk_stuff]) | cut -d: -f2`

    if test "$ndk_key" = "$ndk_module"; then
      ndk_module="$ndk_value"
      break
    fi
  done
}

# Run the Makefile helper script for the Android.mk file.

ndk_run_test () {
  # Figure out where the helper Makefile is.
  ndk_build_helper_file="${ndk_AUX_DIR}ndk-build-helper.mk"
  ndk_module_extract_awk="${ndk_AUX_DIR}ndk-module-extract.awk"
  ndk_dir=`AS_DIRNAME([$ndk_android_mk])`

  # Now call Make with the right arguments.
  "$MAKE" -s -f "$ndk_build_helper_file" EMACS_SRCDIR=`pwd`		\
    EMACS_ABI="$ndk_ABI" ANDROID_MAKEFILE="$ndk_android_mk"		\
    NDK_BUILD_DIR="$ndk_DIR" NDK_ROOT="/tmp"				\
    ANDROID_MODULE_DIRECTORY="$ndk_dir" BUILD_AUXDIR=$ndk_AUX_DIR	\
    NDK_BUILD_ARCH="$ndk_ARCH" 2>&AS_MESSAGE_LOG_FD >conftest.ndk

  # Read the output.
  cat conftest.ndk | awk -f "$ndk_module_extract_awk" MODULE="$ndk_module"

  # Remove the temporary file.
  rm -f conftest.ndk
}

# ndk_parse_pkg_config_string PKG_CONFIG_STRING
# ---------------------------------------------
# Parse a pkg-config style list of modules.  Place the resulting list
# in ndk_modules.

ndk_parse_pkg_config_string () {
  ndk_input=[$]1
  ndk_modules=
  while test -n "$ndk_input"; do
    ndk_str=`AS_ECHO_N(["$ndk_input"]) | cut -f1 -d' '`
    ndk_input=`AS_ECHO_N(["$ndk_input"]) | cut -s -f2- -d' '`

    if test "$ndk_str" = ">=" || test "$ndk_str" = "<=" \
      || test "$ndk_str" = ">" || test "$ndk_str" = "<" \
      || test "$ndk_str" = "!="; then
      ndk_input=`AS_ECHO_N(["$ndk_input"]) | cut -s -f2- -d' '`
    else
      ndk_modules="$ndk_modules$ndk_str "
    fi
  done
}

# ndk_resolve_import_module MODULE
# --------------------------------
# Resolve MODULE, a single import.  Prepend its makefile to
# ndk_MAKEFILES if found.  Also, prepend all includes to the variable
# ndk_import_includes.

ndk_resolve_import_module () {
  module_name=
  ndk_module=[$]1

  AC_MSG_CHECKING([for imported $ndk_module])

  for ndk_android_mk in $ndk_module_files; do
    # Read this Android.mk file.  Set NDK_ROOT to /tmp: the Android in
    # tree build system sets it to a meaningful value, but build files
    # just use it to test whether or not the NDK is being used.
    ndk_commands=`ndk_run_test`
    eval "$ndk_commands"

    if test -n "$module_name"; then
      break;
    fi
  done

  AS_IF([test -z "$module_name"],
    [AC_MSG_RESULT([no])
     AC_MSG_ERROR([The module currently being built depends on [$]1, but \
that could not be found in the list of directories specified in \
`--with-ndk-path'.])])

  if test -n "$module_cxx_deps"; then
    ndk_ANY_CXX=yes
  fi

  AS_IF([test "$module_cxx_deps" = "yes" && test -z "$ndk_CXX_STL" \
         && test -z "$ndk_CXX_LDFLAGS"],
    [AC_MSG_ERROR([The module $1 requires a C++ standard library,
but none were found.])])

  AS_IF([test "$module_cxx_deps" = "yes" && test "$ndk_working_cxx" != "yes"],
    [AC_MSG_ERROR([The module [$]1 requires the C++ standard library,
but a working C++ compiler was not found.])])

  AC_MSG_RESULT([yes])

  # Make sure the module is prepended.
  ndk_MAKEFILES="$ndk_android_mk $ndk_MAKEFILES"
  ndk_import_includes="$module_includes $ndk_import_includes"

  # Now recursively resolve this module's imports.
  for ndk_module in $module_imports; do
    ndk_resolve_import_module $ndk_module
  done
}

# ndk_filter_cc_for_cxx
# ---------------------
# Run through $CC, removing any options that are not suitable for
# use in a C++ compiler.

ndk_filter_cc_for_cxx () {
  for ndk_word in $CC; do
    AS_CASE([$ndk_word], [*-std=*], [],
      [AS_ECHO_N(["$ndk_word "])])
  done
}

# ndk_subst_cc_onto_cxx
# ---------------------
# Print the value of $CXX, followed by any innocent looking options
# in $CC.

ndk_subst_cc_onto_cxx () {
  AS_ECHO_N(["$CXX "])
  ndk_flag=
  for ndk_word in `AS_ECHO_N(["$CC"]) | cut -s -f2- -d' '`; do
    AS_IF([test "$ndk_flag" = "yes"],
      [AS_ECHO_N(["$ndk_word "])
       ndk_flag=no],
      [AS_CASE([$ndk_word],
        [*-sysroot=*],
          [AS_ECHO_N(["$ndk_word "])],
	[*-isystem*],
          [AS_ECHO_N(["$ndk_word "])
	   ndk_flag=yes],
	[*-sysroot*],
	  [AS_ECHO_N(["$ndk_word "])
	   ndk_flag=yes],
	[-D__ANDROID_API__*],
	  [AS_ECHO_N(["$ndk_word "])])])
  done
}

# ndk_subst_cflags_onto_cxx
# ---------------------
# Print any options in CFLAGS also suitable for a C++ compiler.

ndk_subst_cflags_onto_cxx () {
  ndk_flag=
  for ndk_word in $CFLAGS; do
    AS_IF([test "$ndk_flag" = "yes"],
      [AS_ECHO_N(["$ndk_word "])
       ndk_flag=no],
      [AS_CASE([$ndk_word],
        [*-sysroot=*],
          [AS_ECHO_N(["$ndk_word "])],
	[*-isystem*],
          [AS_ECHO_N(["$ndk_word "])
	   ndk_flag=yes],
	[*-I*],
          [AS_ECHO_N(["$ndk_word "])
	   ndk_flag=yes],
	[*-sysroot*],
	  [AS_ECHO_N(["$ndk_word "])
	   ndk_flag=yes],
	[-D__ANDROID_API__*],
	  [AS_ECHO_N(["$ndk_word "])])])
  done
}

# Detect the installation directory and type of the NDK being used.

ndk_install_dir=
ndk_toolchain_type=

AC_MSG_CHECKING([for the directory where the NDK is installed])

dnl If the install directory isn't available, repeat the search over
dnl each entry in the programs directory.
ndk_programs_dirs=`$CC -print-search-dirs | sed -n "s/^programs:[[\t ]]*=\?\(.*\)/\1/p"`
ndk_save_IFS=$IFS; IFS=:
for ndk_dir in $ndk_programs_dirs; do
   if test -d "$ndk_dir"; then :; else
     continue
   fi
   ndk_dir=`cd "$ndk_dir"; pwd`
   while test "$ndk_dir" != "/" && test -z "$ndk_toolchain_type"; do
     ndk_dir=`AS_DIRNAME([$ndk_dir])`
     AS_IF([test -d "$ndk_dir/bin" && test -d "$ndk_dir/lib"],
      [dnl The directory reached is most likely either the directory
       dnl holding prebuilt binaries in a combined toolchain or the
       dnl directory holding a standalone toolchain itself.
       dnl
       dnl Distinguish between the two by verifying the name of the
       dnl parent directory (and its parent).
       ndk_dir1=`AS_DIRNAME(["$ndk_dir"])`
       ndk_basename=`AS_BASENAME(["$ndk_dir1"])`
       AS_IF([test "$ndk_basename" = "prebuilt"],
	 [dnl Directories named "prebuilt" are exclusively present in
	  dnl combined toolchains, where they are children of the
	  dnl base directory or, in recent releases, a directory
	  dnl within the base directory.  Continue searching for the
	  dnl base directory.
	  ndk_toolchain_type=combined
	  while test "$ndk_dir1" != "/"; do
	    AS_IF([test -d "$ndk_dir1/toolchains" \
		   && test -d "$ndk_dir1/sources"],
	      [ndk_install_dir=$ndk_dir1
	       break])
	    ndk_dir1=`AS_DIRNAME(["$ndk_dir1"])`
	  done],
	 [ndk_toolchain_type=standalone
	  ndk_install_dir=$ndk_dir])])
   done
   AS_IF([test -n "$ndk_toolchain_type"],
     [break])
done
IFS=$ndk_save_IFS

AS_IF([test -z "$ndk_install_dir"],
  [AC_MSG_RESULT([unknown])
   AC_MSG_WARN([The NDK installation directory could not be \
derived from the compiler.])],
  [AC_MSG_RESULT([$ndk_install_dir ($ndk_toolchain_type)])])

# Look for a suitable ar and ranlib in the same directory as the C
# compiler.
ndk_cc_firstword=`AS_ECHO(["$CC"]) | cut -d' ' -f1`
ndk_where_cc=`which $ndk_cc_firstword`
ndk_ar_search_path=$PATH
ndk_ranlib_search_path=$RANLIB

# First, try to find $host_alias-ar in PATH.
AC_PATH_PROGS([AR], [$host_alias-ar], [], [$ndk_ar_search_path])

AS_IF([test -z "$AR"],[
  # Next, try finding either that or llvm-ar in the directory holding
  # CC.
  ndk_ar_search_path="`AS_DIRNAME([$ndk_where_cc])`:$ndk_ar_search_path"
  AC_PATH_PROGS([AR], [$host_alias-ar llvm-ar], [], [$ndk_ar_search_path])])

# First, try to find $host_alias-ranlib in PATH.
AC_PATH_PROGS([RANLIB], [$host_alias-ranlib], [], [$ndk_ranlib_search_path])

AS_IF([test -z "$RANLIB"],[
  # Next, try finding either that or llvm-ranlib in the directory
  # holding CC.
  ndk_ranlib_search_path="`AS_DIRNAME([$ndk_where_cc])`:$ndk_ranlib_search_path"
  AC_PATH_PROGS([RANLIB], [$host_alias-ranlib llvm-ranlib], [],
    [$ndk_ranlib_search_path])])

NDK_BUILD_NASM=

# Next, try to find nasm on x86.  This doesn't ship with the NDK.
AS_IF([test "$ndk_ARCH" = "x86" || test "$ndk_ARCH" = "x86_64"],
  [AC_CHECK_PROGS([NDK_BUILD_NASM], [nasm])])

# Search for a suitable readelf binary, which is required to generate
# the shared library list loaded on old Android systems.
AC_PATH_PROGS([READELF], [readelf llvm-readelf $host_alias-readelf],
  [], [$ndk_ranlib_search_path:$PATH])
AS_IF([test -z "$READELF"],
  [AC_MSG_ERROR([A suitable `readelf' utility cannot be located.
Please verify that the Android NDK has been installed correctly,
or install a functioning `readelf' yourself.])])
NDK_BUILD_READELF="$READELF"

# Search for a C++ compiler.  Upon failure, pretend the C compiler is a
# C++ compiler and use that instead.

ndk_cc_name=`AS_BASENAME(["${ndk_cc_firstword}"])`
ndk_cxx_name=

AS_CASE([$ndk_cc_name], [*-gcc],
  [ndk_cxx_name=`AS_ECHO([$ndk_cc_name]) | sed 's/gcc/g++/'`],
  [ndk_cxx_name="${ndk_cc_name}++"])

AS_IF([test -n "$with_ndk_cxx"], [CXX=$with_ndk_cxx],
  [AC_PATH_PROGS([CXX], [$ndk_cxx_name],
     [], [`AS_DIRNAME(["$ndk_where_cc"])`:$PATH])
   AS_IF([test -z "$CXX"], [CXX=`ndk_filter_cc_for_cxx`],
     [CXX=`ndk_subst_cc_onto_cxx`])])

# None of the C++ standard libraries installed with Android are
# available to NDK programs, which are expected to select one of several
# standard libraries distributed with the NDK.  This library must be
# extracted from the NDK by the program's build system and copied into
# the application directory, and the build system is also expected to
# provide the compiler with suitable options to enable it.
#
# Emacs, on recent releases of the NDK, prefers the libc++ library, the
# most complete of the libraries available, when it detects the presence
# of its headers and libraries in the compiler's search path.  Next in
# line are the several libraries located in a directory named `cxx-stl'
# inside the NDK distribution, of which Emacs prefers, in this order,
# the GNU libstdc++, stlport, gabi and the system C++ library.  The
# scope of the last two is confined to providing runtime support for
# basic C++ operations, and is useless for compiling most C++
# dependencies whose requirements go beyond such operations.
#
# The NDK comes in two forms.  In a "combined toolchain", all C++
# libraries are present in the NDK directory and the responsibility is
# left to the build system to locate and select the best C++ library,
# whereas in a "standalone toolchain" an STL will have already been
# specified a C++ library, besides which no others will be present.
#
# Though Android.mk files are provided by the NDK for each such library,
# Emacs cannot use any of these, both for lack of prebuilt support in
# its ndk-build implementation, and since they are absent from combined
# toolchains.

ndk_CXX_SHARED=
ndk_CXX_STL=
ndk_CXX_LDFLAGS=

AS_IF([test -n "$CXX" && test -n "$ndk_install_dir"],
  [ndk_library_dirs=`$CXX -print-search-dirs \
                      | sed -n "s/^libraries:[[\t ]]*=\?\(.*\)/\1/p"`
   AS_IF([test "$ndk_toolchain_type" = "standalone"],
    [dnl With a standalone toolchain, just use the first C++ library
     dnl present in the compiler's library search path, that being the
     dnl only C++ library that will ever be present.
     ndk_save_IFS=$IFS; IFS=:
     for ndk_dir in $ndk_library_dirs; do
       if test -d "$ndk_dir"; then :; else
	 continue
       fi
       ndk_dir=`cd "$ndk_dir"; pwd`
       if test -f "$ndk_dir/libc++_shared.so"; then
         ndk_CXX_SHARED="$ndk_dir/libc++_shared.so"
         ndk_CXX_LDFLAGS=-lc++_shared; break
       elif test -f "$ndk_dir/libgnustl_shared.so"; then
         ndk_CXX_SHARED="$ndk_dir/libgnustl_shared.so"
         ndk_CXX_LDFLAGS=-lgnustl_shared; break
       elif test -f "$ndk_dir/libstlport_shared.so"; then
         ndk_CXX_SHARED="$ndk_dir/libstlport_shared.so"
	 ndk_CXX_LDFLAGS=-lstlport_shared; break
       fi
     done
     IFS=$ndk_save_IFS],
    [dnl Otherwise, search for a suitable standard library
     dnl in the order stated above.
     dnl
     dnl Detect if this compiler is configured to link against libc++ by
     dnl default.
     AC_MSG_CHECKING([whether compiler defaults to libc++])
     cat <<_ACEOF >conftest.cc
#include <string>
#ifndef _LIBCPP_VERSION
Not libc++!
#endif /* _LIBCPP_VERSION */

int
main (void)
{

}
_ACEOF
     AS_IF([$CXX conftest.cc -o conftest.o >&AS_MESSAGE_LOG_FD 2>&1],
       [dnl The compiler defaults to libc++.
        AC_MSG_RESULT([yes])
	ndk_save_IFS=$IFS; IFS=:
	for ndk_dir in $ndk_library_dirs; do
	  if test -f "$ndk_dir/libc++_shared.so"; then
	    ndk_CXX_SHARED="$ndk_dir/libc++_shared.so"
	    ndk_CXX_LDFLAGS=-lc++_shared; break
	  fi
	done
	IFS=$ndk_save_IFS],
       [dnl Search for gnustl, stlport, gabi, and failing that, system.
        dnl The name of the gabi system root directory varies by GCC
        dnl version.
        AC_MSG_RESULT([no])
        ndk_gcc_version=`($CXX -v 2>&1) \
	 | sed -n "s/^gcc version \([[0123456789]\+.[0123456789]\+]\).*/\1/p"`
	cxx_stl="$ndk_install_dir/sources/cxx-stl"
	ndk_cxx_stl_base="$cxx_stl/gnu-libstdc++/$ndk_gcc_version"
	AS_IF([test -n "$ndk_gcc_version" \
	       && test -d "$ndk_cxx_stl_base/libs/$ndk_ABI"],
	  [ndk_CXX_LDFLAGS="-L$ndk_cxx_stl_base/libs/$ndk_ABI -lgnustl_shared"
	   ndk_CXX_LDFLAGS="$ndk_CXX_LDFLAGS -lsupc++"
	   ndk_CXX_STL="-isystem $ndk_cxx_stl_base/include"
	   ndk_CXX_STL="$ndk_CXX_STL -isystem $ndk_cxx_stl_base/libs/$ndk_ABI/include"
	   ndk_CXX_SHARED="$ndk_cxx_stl_base/libs/$ndk_ABI/libgnustl_shared.so"])
	AS_IF([test -f "$ndk_CXX_SHARED"], [],
	  [dnl No STL was located or the library is not reachable.
	   dnl Search for alternatives.
	   ndk_CXX_STL=
	   ndk_CXX_SHARED=
	   ndk_CXX_LDFLAGS=
	   ndk_cxx_stl_base="$cxx_stl/stlport"
	   AS_IF([test -d "$ndk_cxx_stl_base"],
	     [ndk_CXX_LDFLAGS="-L$ndk_cxx_stl_base/libs/$ndk_ABI -lstlport_shared"
	      ndk_CXX_STL="-isystem $ndk_cxx_stl_base/stlport"
	      ndk_CXX_SHARED="$ndk_cxx_stl_base/libs/$ndk_ABI/libstlport_shared.so"])
           AS_IF([test -f "$ndk_CXX_SHARED"], [],
	     [ndk_CXX_STL=
	      ndk_CXX_SHARED=
	      ndk_CXX_LDFLAGS=
	      ndk_cxx_stl_base="$cxx_stl/gabi++"
	      AS_IF([test -d "$ndk_cxx_stl_base"],
	       [ndk_CXX_LDFLAGS="-L$ndk_cxx_stl_base/libs/$ndk_ABI -lgabi++_shared"
	        ndk_CXX_STL="$ndk_CXX_STL -isystem $ndk_cxx_stl_base/include"
	        ndk_CXX_SHARED="$ndk_cxx_stl_base/libs/$ndk_ABI/lgabi++_shared.so"])])
           AS_IF([test -f "$ndk_CXX_SHARED"], [],
	     [ndk_CXX_STL=
	      ndk_CXX_SHARED=
	      ndk_CXX_LDFLAGS=
	      ndk_cxx_stl_base="$cxx_stl/system"
	      AS_IF([test -d "$ndk_cxx_stl_base"],
	       [ndk_CXX_LDFLAGS="-L$ndk_cxx_stl_base/libs/$ndk_ABI -lstdc++"
                ndk_CXX_STL="-isystem $ndk_cxx_stl_base/include"
	        dnl The "system" library is distributed with Android and
	        dnl need not be present in app packages.
	        ndk_CXX_SHARED=
		dnl Done.
		])])])])
     rm -f conftest.o])])

AS_ECHO([])
AS_ECHO(["C++ compiler configuration: "])
AS_ECHO([])
AS_ECHO(["Library includes        : $ndk_CXX_STL"])
AS_ECHO(["Linker options          : $ndk_CXX_LDFLAGS"])
AS_ECHO(["Library file (if any)   : $ndk_CXX_SHARED"])
AS_ECHO([])
])

# ndk_LATE_EARLY
# --------------
# Call before ndk_LATE to establish certain variables in time for
# ndk_LATE's C++ compiler detection.

AC_DEFUN([ndk_LATE_EARLY],
[ndk_save_LDFLAGS="$LDFLAGS"
 LDFLAGS="$LDFLAGS $ndk_CXX_LDFLAGS"
 CXXFLAGS="$CXXFLAGS `ndk_subst_cflags_onto_cxx` $ndk_CXX_STL"])

# ndk_LATE
# --------
# Perform late initialization of the ndk-build system by checking for
# required C and C++ headers.

AC_DEFUN([ndk_LATE],
[dnl
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 configured, as \
the standard library headers could not be found.])])
    AC_LANG_POP([C++])])])
LDFLAGS="$ndk_save_LDFLAGS"
])

# ndk_SEARCH_MODULE(MODULE, NAME, ACTION-IF-FOUND, [ACTION-IF-NOT-FOUND])
# -----------------------------------------------------------------------
# Search for a module named MODULE in `with_ndk_path'.  Add the file
# name of the module's Android.mk file to the variable ndk_MAKEFILES.
# Set NAME_CFLAGS and NAME_LIBS to the appropriate values.  Then, call
# ACTION-IF-FOUND, or ACTION-IF-NOT-FOUND upon failure.
#
# Resolve any imports specified by MODULE, and expand AC_MSG_ERROR
# with a suitable error message if imports were not found.
AC_DEFUN([ndk_SEARCH_MODULE],
[
module_name=
ndk_module=$1
ndk_replace_pkg_config_package
AC_MSG_CHECKING([for Android.mk that builds $ndk_module])

for ndk_android_mk in $ndk_module_files; do
  # Read this Android.mk file.  Set NDK_ROOT to /tmp: the Android in
  # tree build system sets it to a meaning value, but build files just
  # use it to test whether or not the NDK is being used.
  ndk_commands=`ndk_run_test`

  eval "$ndk_commands"
  if test -n "$module_name"; then
    break;
  fi
done

if test -z "$module_name"; then
  AC_MSG_RESULT([no])
  $4
else
  if test -n "$module_cxx_deps"; then
    ndk_ANY_CXX=yes
  fi

  AS_IF([test "$module_cxx_deps" = "yes" && test -z "$ndk_CXX_STL" \
         && test -z "$ndk_CXX_LDFLAGS"],
    [AC_MSG_ERROR([The module $1 requires a C++ standard library,
but none were found.])])

  AS_IF([test "$module_cxx_deps" = "yes" && test "$ndk_working_cxx" != "yes"],
    [AC_MSG_ERROR([The module [$]1 requires the C++ standard library,
but a working C++ compiler was not found.])])

  $2[]_CFLAGS="[$]$2[]_CFLAGS $module_cflags $module_includes"
  $2[]_LIBS="[$]$2[]_LIBS $module_ldflags"
  ndk_MAKEFILES="$ndk_MAKEFILES $ndk_android_mk"
  ndk_MODULES="$ndk_MODULES $module_target"
  AC_MSG_RESULT([yes])
  $3

  # Now, resolve imports.  Make sure the imports' Makefiles comes
  # before ndk_MAKEFILES; likewise for its includes.
  ndk_import_includes=
  for ndk_module in $module_imports; do
    ndk_resolve_import_module $ndk_module
    $2[]_CFLAGS="$ndk_import_includes [$]$2[]_CFLAGS"
  done
fi
])

# ndk_CHECK_MODULES(VARIABLE-PREFIX, MODULES, [ACTION-IF-FOUND],
#   [ACTION-IF-NOT-FOUND])
# --------------------------------------------------------------
# Just like `PKG_CHECK_MODULES'.  However, it uses the ndk-build
# system instead.

AC_DEFUN([ndk_CHECK_MODULES],
[
  ndk_modules=
  ndk_parse_pkg_config_string "$2"
  ndk_found=no

  for module in $ndk_modules; do
    ndk_SEARCH_MODULE([$module], [$1], [ndk_found=yes], [ndk_found=no])
  done

  AS_IF([test "$ndk_found" = "yes"],[$3],[$4])
])

# ndk_CONFIG_FILES
# -------------------------------------------------------------
# Write out the NDK build Makefile with the appropriate variables
# set if the NDK has been initialized.

AC_DEFUN_ONCE([ndk_CONFIG_FILES],
[
  if test "$ndk_INITIALIZED" = "yes"; then
    NDK_BUILD_ANDROID_MK="$ndk_MAKEFILES"
    NDK_BUILD_ARCH=$ndk_ARCH
    NDK_BUILD_ABI=$ndk_ABI
    NDK_BUILD_SDK=$ndk_API
    NDK_BUILD_CC=$CC
    NDK_BUILD_CXX=$CXX
    NDK_BUILD_AR=$AR
    NDK_BUILD_MODULES="$ndk_MODULES"
    NDK_BUILD_CXX_SHARED="$ndk_CXX_SHARED"
    NDK_BUILD_CXX_STL="$ndk_CXX_STL"
    NDK_BUILD_CXX_LDFLAGS="$ndk_CXX_LDFLAGS"
    NDK_BUILD_ANY_CXX_MODULE=$ndk_ANY_CXX
    NDK_BUILD_CFLAGS="$ndk_BUILD_CFLAGS"

    AC_SUBST([NDK_BUILD_ANDROID_MK])
    AC_SUBST([NDK_BUILD_ARCH])
    AC_SUBST([NDK_BUILD_ABI])
    AC_SUBST([NDK_BUILD_SDK])
    AC_SUBST([NDK_BUILD_CC])
    AC_SUBST([NDK_BUILD_CXX])
    AC_SUBST([NDK_BUILD_AR])
    AC_SUBST([NDK_BUILD_NASM])
    AC_SUBST([NDK_BUILD_MODULES])
    AC_SUBST([NDK_BUILD_CXX_SHARED])
    AC_SUBST([NDK_BUILD_CXX_STL])
    AC_SUBST([NDK_BUILD_CXX_LDFLAGS])
    AC_SUBST([NDK_BUILD_ANY_CXX_MODULE])
    AC_SUBST([NDK_BUILD_CFLAGS])
    AC_SUBST([NDK_BUILD_READELF])

    AC_CONFIG_FILES([$ndk_DIR/Makefile])
    AC_CONFIG_FILES([$ndk_DIR/ndk-build.mk])
  fi
])