diff -ur gc-7.6.4.old/include/private/gcconfig.h gc-7.6.4.new/include/private/gcconfig.h

--- gc-7.6.4.old/include/private/gcconfig.h	2018-01-26 13:16:17.000000000 +0000

+++ gc-7.6.4.new/include/private/gcconfig.h	2018-02-27 09:33:05.840680540 +0000

@@ -602,6 +602,15 @@

 #   define I386

 #   define mach_type_known

 # endif

+# if defined(__riscv) && defined(LINUX)

+#   if __riscv_xlen == 32

+#     define RISCV32

+#     define mach_type_known

+#   elif __riscv_xlen == 64

+#     define RISCV64

+#     define mach_type_known

+#   endif

+# endif

 /* Feel free to add more clauses here */

@@ -2650,6 +2659,32 @@

 #   endif

 # endif

+# ifdef RISCV32

+#   define CPP_WORDSZ 32

+#   define MACH_TYPE "RISC-V32"

+#   define ALIGNMENT 4

+#   ifdef LINUX

+#     define OS_TYPE "LINUX"

+      extern int __data_start[];

+#     define DATASTART ((ptr_t)__data_start)

+#     define LINUX_STACKBOTTOM

+#     define DYNAMIC_LOADING

+#   endif

+# endif /* RISCV32 */

+

+# ifdef RISCV64

+#   define CPP_WORDSZ 64

+#   define MACH_TYPE "RISC-V64"

+#   define ALIGNMENT 8

+#   ifdef LINUX

+#     define OS_TYPE "LINUX"

+      extern int __data_start[];

+#     define DATASTART ((ptr_t)__data_start)

+#     define LINUX_STACKBOTTOM

+#     define DYNAMIC_LOADING

+#   endif

+# endif /* RISCV64 */

+

 #if defined(__GLIBC__) && !defined(DONT_USE_LIBC_PRIVATES)

   /* Use glibc's stack-end marker. */

 # define USE_LIBC_PRIVATES