Index: libcxx/trunk/include/__config
===================================================================
--- libcxx/trunk/include/__config
+++ libcxx/trunk/include/__config
@@ -45,6 +45,8 @@
 #define _LIBCPP_OBJECT_FORMAT_MACHO 1
 #elif defined(_WIN32)
 #define _LIBCPP_OBJECT_FORMAT_COFF  1
+#elif defined(__wasm__)
+#define _LIBCPP_OBJECT_FORMAT_WASM  1
 #else
 #error Unknown object file format
 #endif
Index: libcxx/trunk/src/include/config_elast.h
===================================================================
--- libcxx/trunk/src/include/config_elast.h
+++ libcxx/trunk/src/include/config_elast.h
@@ -24,7 +24,7 @@
 #define _LIBCPP_ELAST __ELASTERROR
 #elif defined(__Fuchsia__)
 // No _LIBCPP_ELAST needed on Fuchsia
-#elif defined(__linux__)
+#elif defined(__linux__) || defined(_LIBCPP_HAS_MUSL_LIBC)
 #define _LIBCPP_ELAST 4095
 #elif defined(__APPLE__)
 // No _LIBCPP_ELAST needed on Apple