Added some checks to hopefully better compile with Android NDK

README.md

@@ -40,15 +40,18 @@ evolved with C++11 and the following standards. Keep on the good work!
 It should work on any of these with a C++11-capable compiler. I currently
 don't have a BSD derivate besides macOS, so the preprocessor checks will
 cry out if you try to use it there, but if there is demand, I can try to
-help. Still, it shouldn't replace `std::filesystem` where full C++17 is
-available, it doesn't try to be a "better" `std::filesystem`, just a drop-in
-if you can't use it.
+help. Also there are some checks to hopefully better work on Android, but
+as I currently don't test with the Android NDK, I wouldn't call it a
+supported platform yet. All in all, I don't see it replacing `std::filesystem`
+where full C++17 is available, it doesn't try to be a "better"
+`std::filesystem`, just a drop-in if you can't use it (with the exception
+of the UTF-8 preference on Windows).
 
 Tests are currently run with:
 
 * macOS 10.12: XCode 9.2 (clang-900.0.39.2), GCC 8.1.0, Clang 7.0.0
 * Windows 10: Visual Studio 2017 15.8.5, MingW GCC 5.3
-* Linux: Ubuntu 18.04LTS GCC 7.3 & GCC 8.0.1
+* Linux: Ubuntu 18.04LTS GCC 7.3 & GCC 8.2.0
 
 
 ## Tests
@@ -72,11 +75,12 @@ make
 This generates `filesystem_test`, the binary that runs all tests.
 
 If the default compiler is a GCC 8 or newer, or Clang 7 or newer, it
-additionally builds a version of the test binary compiled against GCCs/Clangs
+additionally tries to build a version of the test binary compiled against GCCs/Clangs
 `std::filesystem` implementation, named `std_filesystem_test`
 as an additional test of conformance. Ideally all tests should compile and
 succeed with all filesystem implementations, but in reality, there are
-some differences in behavior and might be issues in these implementations.
+some differences in behavior, sometimes due to room for interpretation in
+in the standard, and there might be issues in these implementations too.
 
 
 ## Usage
@@ -355,6 +359,8 @@ to the expected behavior.
 
 * Bugfix for ([#9](https://github.com/gulrak/filesystem/issues/9)), added
   missing return statement to `ghc::filesystem::path::generic_string()`
+* Added checks to hopefully better compile against Android NDK. There where
+  no tests run yet, so feedback is needed to actually call this supported.
 
 ### [v1.0.8](https://github.com/gulrak/filesystem/releases/tag/v1.0.8)
 

examples/dir.cpp

@@ -21,7 +21,7 @@ std::time_t to_time_t(TP tp)
 static std::string perm_to_str(fs::perms prms)
 {
     std::string result;
-    result.reserve(6);
+    result.reserve(9);
     for(int i = 0; i < 9; ++i) {
         result = ((static_cast<int>(prms) & (1<<i)) ? "xwrxwrxwr"[i] : '-') + result;
     }

filesystem.h

@@ -79,6 +79,10 @@
 #include <sys/time.h>
 #include <sys/types.h>
 #include <unistd.h>
+#if defined(__ANDROID__)
+#define GHC_OS_ANDROID
+#include <android/api-level.h>
+#endif
 #endif
 #ifdef GHC_OS_MACOS
 #include <Availability.h>
@@ -1276,14 +1280,14 @@ inline std::string systemErrorText(ErrorNumber code = 0)
     std::string msg = toUtf8(std::wstring((LPWSTR)msgBuf));
     LocalFree(msgBuf);
     return msg;
-#elif defined(GHC_OS_LINUX)
+#elif defined(GHC_OS_MACOS) || ((_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) && !defined(_GNU_SOURCE)) || (defined(GHC_OS_ANDROID) && __ANDROID_API__<23)
+    char buffer[512];
+    int rc = strerror_r(code ? code : errno, buffer, sizeof(buffer));
+    return rc == 0 ? (const char*)buffer : "Error in strerror_r!"
+#else
     char buffer[512];
     char* msg = strerror_r(code ? code : errno, buffer, sizeof(buffer));
     return msg ? msg : buffer;
-#elif defined(GHC_OS_MACOS)
-    char buffer[512];
-    int rc = strerror_r(code ? code : errno, buffer, sizeof(buffer));
-    return rc == 0 ? (const char*)buffer : "Error in strerror_r!";
 #endif
 }
 
@@ -1679,10 +1683,14 @@ inline u8arguments::u8arguments(int& argc, char**& argv)
     _isvalid = true;
 #else
     std::setlocale(LC_ALL, "");
+#if defined(__ANDROID__) && __ANDROID_API__ < 26
+    _isvalid = true;
+#else
     if (!detail::compare_no_case(::nl_langinfo(CODESET), "UTF-8")) {
         _isvalid = true;
     }
 #endif
+#endif
 }
 
 //-----------------------------------------------------------------------------
@@ -3800,13 +3808,16 @@ inline space_info space(const path& p, std::error_code& ec) noexcept
         return {static_cast<uintmax_t>(-1), static_cast<uintmax_t>(-1), static_cast<uintmax_t>(-1)};
     }
     return {static_cast<uintmax_t>(totalNumberOfBytes.QuadPart), static_cast<uintmax_t>(totalNumberOfFreeBytes.QuadPart), static_cast<uintmax_t>(freeBytesAvailableToCaller.QuadPart)};
-#else
+#elif !defined(__ANDROID__) || __ANDROID_API__ >= 19
     struct ::statvfs sfs;
     if (::statvfs(p.c_str(), &sfs) != 0) {
         ec = std::error_code(errno, std::system_category());
         return {static_cast<uintmax_t>(-1), static_cast<uintmax_t>(-1), static_cast<uintmax_t>(-1)};
     }
     return {static_cast<uintmax_t>(sfs.f_blocks * sfs.f_frsize), static_cast<uintmax_t>(sfs.f_bfree * sfs.f_frsize), static_cast<uintmax_t>(sfs.f_bavail * sfs.f_frsize)};
+#else
+    ec = detail::make_error_code(detail::portable_error::not_supported);
+    return {static_cast<uintmax_t>(-1), static_cast<uintmax_t>(-1), static_cast<uintmax_t>(-1)};
 #endif
 }