getsubopt: Fix compilation error in C++ mode on Android

[Bruno Haible]

In a testdir on Android, I get this compilation error:

clang++ -ferror-limit=0 -DHAVE_CONFIG_H -DEXEEXT=\"\" -DEXEEXT=\"\" -I. 
-I../../gltests -I..  -DGNULIB_STRICT_CHECKING=1 -DIN_GNULIB_TESTS=1 -I. 
-I../../gltests -I.. -I../../gltests/.. -I../gllib -I../../gltests/../gllib 
-I/data/data/com.termux/files/home/local/include -Wall  -Wno-error -g -O2 -c -o 
test-stdlib-c++.o ../../gltests/test-stdlib-c++.cc

In file included from ../../gltests/test-stdlib-c++.cc:22:
In file included from ../gllib/stdlib.h:36:
In file included from 
/data/data/com.termux/files/usr/include/c++/v1/stdlib.h:97:
In file included from /data/data/com.termux/files/usr/include/stdlib.h:276:
In file included from 
/data/data/com.termux/files/usr/include/android/legacy_stdlib_inlines.h:91:
../gllib/stdlib.h:1002:19: error: no member named 'getsubopt' in the global 
namespace; did you mean 'getopt'?
_GL_CXXALIAS_SYS (getsubopt, int,
~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
In file included from ../../gltests/test-stdlib-c++.cc:22:
In file included from ../gllib/stdlib.h:36:
In file included from 
/data/data/com.termux/files/usr/include/c++/v1/stdlib.h:97:
In file included from /data/data/com.termux/files/usr/include/stdlib.h:276:
In file included from 
/data/data/com.termux/files/usr/include/android/legacy_stdlib_inlines.h:91:
../gllib/stdlib.h:1002:1: error: cannot initialize return object of type 
'gnulib::_gl_getsubopt_wrapper::type' (aka 'int (*)(char **, char *const *, 
char **)') with an lvalue of type 'int (int, char *const *, const char *)': 
type mismatch at 1st parameter ('char **' vs 'int')
_GL_CXXALIAS_SYS (getsubopt, int,
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../../gltests/test-stdlib-c++.cc:22:
In file included from ../gllib/stdlib.h:36:
In file included from 
/data/data/com.termux/files/usr/include/c++/v1/stdlib.h:97:
In file included from /data/data/com.termux/files/usr/include/stdlib.h:276:
In file included from 
/data/data/com.termux/files/usr/include/android/legacy_stdlib_inlines.h:91:
../gllib/stdlib.h:1004:19: error: use of undeclared identifier 'getsubopt'; did 
you mean 'gnulib::getsubopt'?
_GL_CXXALIASWARN (getsubopt);
                  ^

The cause is that the function getsubopt is declared only for a later API level
of Android:
/usr/include/stdlib.h:int getsubopt(char** __option, char* const* __tokens, 
char** __value_ptr) __INTRODUCED_IN(26);

This patch fixes the error.


2023-01-09  Bruno Haible  <bruno@clisp.org>

        getsubopt: Fix compilation error in C++ mode on Android.
        * m4/getsubopt.m4 (gl_FUNC_GETSUBOPT): Use gl_CHECK_FUNCS_ANDROID
        instead of AC_CHECK_FUNCS_ONCE.

diff --git a/m4/getsubopt.m4 b/m4/getsubopt.m4
index 0753b1f64c..a528ec7143 100644
--- a/m4/getsubopt.m4
+++ b/m4/getsubopt.m4
@@ -1,4 +1,4 @@
-# getsubopt.m4 serial 5
+# getsubopt.m4 serial 6
 dnl Copyright (C) 2004, 2007, 2009-2023 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -10,7 +10,10 @@ AC_DEFUN([gl_FUNC_GETSUBOPT],
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
   AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
-  AC_CHECK_FUNCS_ONCE([getsubopt])
+  gl_CHECK_FUNCS_ANDROID([getsubopt],
+    [[#include <stdlib.h>
+      #include <unistd.h>
+    ]])
   if test $ac_cv_func_getsubopt = no; then
     HAVE_GETSUBOPT=0
   fi