cffi-libffi doesn't build with libffi from git due to changes in available ABIs (FFI_SYSV undefined)

[vydd]

Loading cffi on openSuse Tumbleweed results in two errors.

The first one,

(FL-ERROR "Unable to load any of the alternatives:~% ~S" ("libffi.so.6" "libffi32.so.6" "libffi.so.5" "libffi32.so.5"))

is easily solved by providing ("libffi.so") as a value to be used instead.

This is because Tumbleweed comes with libffi7, from git. As far as I can tell from
their package changelog, it's https://github.com/libffi/libffi/tree/60e4250a77eb3fde500bfd68ec40519fe34b21bd .

This leads to another problem:

grov.c: In function ‘main’:
grov.c:72:41: error: ‘FFI_SYSV’ undeclared (first use in this function)
   fprintf(output, "%"PRIiMAX, (intmax_t)FFI_SYSV);

FFI_SYSV isn't defined because ffi_abi struct in ffitarget.h resolves to

#elif defined(X86_64) || (defined (__x86_64__) && defined (X86_DARWIN))
  FFI_FIRST_ABI = 1,
  FFI_UNIX64,
  FFI_WIN64,
  FFI_EFI64 = FFI_WIN64,
  FFI_LAST_ABI,
  FFI_DEFAULT_ABI = FFI_UNIX64

leaving FFI_SYSV undefined.

As a temporary fix, I added #define FFI_SYSV 1 to grovel/common.h, and compiling worked
just fine for my case (https://github.com/vydd/sketch/issues/17#issuecomment-303260982),
but a proper patch is needed.

EDIT: Proposed patch

2 files changed, 7 insertions(+), 2 deletions(-)
libffi/libffi-types.lisp | 7 ++++++-
libffi/libffi.lisp | 2 +-

modified libffi/libffi-types.lisp
@@ -65,7 +65,12 @@
  ((:sysv "FFI_SYSV"))
  ((:stdcall "FFI_STDCALL")))

-#-(or freebsd windows)
+#+(and x86-64 (not windows))
+(cenum abi
+ ((:default-abi "FFI_DEFAULT_ABI"))
+ ((:unix64 "FFI_UNIX64")))
+
+#-(or freebsd windows x86-64)
 (cenum abi
  ((:default-abi "FFI_DEFAULT_ABI"))
  ((:sysv "FFI_SYSV"))
modified libffi/libffi.lisp
@@ -31,7 +31,7 @@
   (:darwin (:or "libffi.dylib" "libffi32.dylib" "/usr/lib/libffi.dylib"))
   (:solaris (:or "/usr/lib/amd64/libffi.so" "/usr/lib/libffi.so"))
   (:openbsd "libffi.so")
- (:unix (:or "libffi.so.6" "libffi32.so.6" "libffi.so.5" "libffi32.so.5"))
+ (:unix (:or "libffi.so.6" "libffi32.so.6" "libffi.so.5" "libffi32.so.5" "libffi.so"))
   (:windows (:or "libffi-6.dll" "libffi-5.dll" "libffi.dll"))
(t (:default "libffi")))

I don't know nearly enough about cffi internals to be sure it doesn't break other stuff. Otherwise I'd post this as a pull request.