diff --git a/libstdc++-v3/config/os/generic/error_constants.h b/libstdc++-v3/config/os/generic/error_constants.h
index 4d900414494c733f19c66d6ed6d4eba06990327c..ba2795352bcc86619759839f7385ce3ccf47f531 100644
--- a/libstdc++-v3/config/os/generic/error_constants.h
+++ b/libstdc++-v3/config/os/generic/error_constants.h
@@ -167,6 +167,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 #ifdef EOVERFLOW
       value_too_large = 			EOVERFLOW,
+#elif defined __AVR__
+      value_too_large = 			999,
 #endif
 
       wrong_protocol_type = 			EPROTOTYPE
diff --git a/libstdc++-v3/src/c++11/system_error.cc b/libstdc++-v3/src/c++11/system_error.cc
index 6e7c0ac0c26cc0be1f63711ddd8ee83ab5dc2abe..748eee941681849747cf30bbf954d3f6b0cd064b 100644
--- a/libstdc++-v3/src/c++11/system_error.cc
+++ b/libstdc++-v3/src/c++11/system_error.cc
@@ -251,6 +251,15 @@ namespace
 	X (WRITE_PROTECT,		EROFS);
 #undef X
 
+#elif defined __AVR__
+      // avr-libc only defines a few distinct error numbers. Most <errno.h>
+      // constants are not usable in #if directives and have the same value.
+      case EDOM:
+      case ERANGE:
+      case ENOSYS:
+      case EINTR:
+      case 0:
+	return std::error_condition(ev, generic_category_instance.obj);
 #else
       // List of errno macros from [cerrno.syn].
       // C11 only defines EDOM, EILSEQ and ERANGE, the rest are from POSIX.
diff --git a/libstdc++-v3/src/c++17/fs_ops.cc b/libstdc++-v3/src/c++17/fs_ops.cc
index b49bf4a6b2093407a424a75e7df3210c1c0eee98..c94d260632f68fdeebbb1ea42deca64af0ea23b5 100644
--- a/libstdc++-v3/src/c++17/fs_ops.cc
+++ b/libstdc++-v3/src/c++17/fs_ops.cc
@@ -736,7 +736,7 @@ fs::path
 fs::current_path(error_code& ec)
 {
   path p;
-#ifdef _GLIBCXX_HAVE_UNISTD_H
+#if defined _GLIBCXX_HAVE_UNISTD_H && ! defined __AVR__
 #if defined __GLIBC__ || defined _GLIBCXX_FILESYSTEM_IS_WINDOWS
   if (char_ptr cwd = char_ptr{posix::getcwd(nullptr, 0)})
     {
@@ -1302,6 +1302,7 @@ fs::remove_all(const path& p)
     }
     // Directory is empty now, will remove it below.
     break;
+#ifndef __AVR__
   case ENOENT:
     // Our work here is done.
     return 0;
@@ -1309,6 +1310,7 @@ fs::remove_all(const path& p)
   case ELOOP:
     // Not a directory, will remove below.
     break;
+#endif
   default:
     // An error occurred.
     _GLIBCXX_THROW_OR_ABORT(filesystem_error("cannot remove all", p, ec));
@@ -1339,6 +1341,7 @@ fs::remove_all(const path& p, error_code& ec)
     }
     // Directory is empty now, will remove it below.
     break;
+#ifndef __AVR__
   case ENOENT:
     // Our work here is done.
     ec.clear();
@@ -1347,6 +1350,7 @@ fs::remove_all(const path& p, error_code& ec)
   case ELOOP:
     // Not a directory, will remove below.
     break;
+#endif
   default:
     // An error occurred.
     return -1;
diff --git a/libstdc++-v3/src/filesystem/ops-common.h b/libstdc++-v3/src/filesystem/ops-common.h
index b0d49dd4d4f866e76bdebfe3cb762b52663b1859..02c75be09d2060c180b2c5414f3d77cd2999005b 100644
--- a/libstdc++-v3/src/filesystem/ops-common.h
+++ b/libstdc++-v3/src/filesystem/ops-common.h
@@ -167,7 +167,7 @@ namespace __gnu_posix
     return ret;
   }
   using char_type = wchar_t;
-#elif defined _GLIBCXX_HAVE_UNISTD_H
+#elif defined _GLIBCXX_HAVE_UNISTD_H && ! defined __AVR__
   using ::open;
   using ::close;
 # ifdef _GLIBCXX_HAVE_SYS_STAT_H