From 866d83579e5181c9eb702ee81629563830b5c727 Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Thu, 8 Jun 2023 09:06:34 -0500
Subject: [PATCH] Address #1165 - Allow for partial ffi support without totally
 removing testing.

Query at runtime which calling conventions are supported, including
a placeholder :none.
---
 src/core/ffi.c       | 22 ++++++++++++++++++++++
 test/suite-ffi.janet |  9 +++++++--
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/src/core/ffi.c b/src/core/ffi.c
index c61cc3da..8fcf7d3c 100644
--- a/src/core/ffi.c
+++ b/src/core/ffi.c
@@ -1364,6 +1364,7 @@ JANET_CORE_FN(cfun_ffi_call,
     switch (signature->cc) {
         default:
         case JANET_FFI_CC_NONE:
+            (void) function_pointer;
             janet_panic("calling convention not supported");
 #ifdef JANET_FFI_WIN64_ENABLED
         case JANET_FFI_CC_WIN_64:
@@ -1529,6 +1530,26 @@ JANET_CORE_FN(cfun_ffi_pointer_buffer,
     return janet_wrap_buffer(janet_pointer_buffer_unsafe(offset_pointer, capacity, count));
 }
 
+JANET_CORE_FN(cfun_ffi_supported_calling_conventions,
+        "(ffi/calling-conventions)",
+        "Get an array of all supported calling conventions on the current arhcitecture. Some architectures may have some FFI "
+        "functionality (ffi/malloc, ffi/free, ffi/read, ffi/write, etc.) but not support "
+        "any calling conventions. This function can be used to get all supported calling conventions "
+        "that can be used on this architecture. All architectures support the :none calling "
+        "convention which is a placeholder that cannot be used at runtime.") {
+    janet_fixarity(argc, 0);
+    (void) argv;
+    JanetArray *array = janet_array(4);
+#ifdef JANET_FFI_WIN64_ENABLED
+    janet_array_push(array, janet_ckeywordv("win64"));
+#endif
+#ifdef JANET_FFI_SYSV64_ENABLED
+    janet_array_push(array, janet_ckeywordv("sysv64"));
+#endif
+    janet_array_push(array, janet_ckeywordv("none"));
+    return janet_wrap_array(array);
+}
+
 void janet_lib_ffi(JanetTable *env) {
     JanetRegExt ffi_cfuns[] = {
         JANET_CORE_REG("ffi/native", janet_core_raw_native),
@@ -1546,6 +1567,7 @@ void janet_lib_ffi(JanetTable *env) {
         JANET_CORE_REG("ffi/malloc", cfun_ffi_malloc),
         JANET_CORE_REG("ffi/free", cfun_ffi_free),
         JANET_CORE_REG("ffi/pointer-buffer", cfun_ffi_pointer_buffer),
+        JANET_CORE_REG("ffi/calling-conventions", cfun_ffi_supported_calling_conventions),
         JANET_REG_END
     };
     janet_core_cfuns_ext(env, NULL, ffi_cfuns);
diff --git a/test/suite-ffi.janet b/test/suite-ffi.janet
index 42fb95d4..6ad4f70c 100644
--- a/test/suite-ffi.janet
+++ b/test/suite-ffi.janet
@@ -22,7 +22,12 @@
 (start-suite)
 
 # We should get ARM support...
-(def has-ffi (and (dyn 'ffi/native) (= (os/arch) :x64)))
+(def has-ffi (dyn 'ffi/native))
+(def has-full-ffi
+  (and has-ffi
+       (when-let [entry (dyn 'ffi/calling-conventions)]
+         (def fficc (entry :value))
+         (> (length (fficc)) 1)))) # all arches support :none
 
 # FFI check
 # d80356158
@@ -31,7 +36,7 @@
 
 (compwhen has-ffi
   (ffi/defbind memcpy :ptr [dest :ptr src :ptr n :size]))
-(compwhen has-ffi
+(compwhen has-full-ffi
   (def buffer1 @"aaaa")
   (def buffer2 @"bbbb")
   (memcpy buffer1 buffer2 4)