FEAT: added simple test extension + handling RXR_BAD_ARGS value from extension command call

resolves: Oldes/Rebol-issues#1867

Author: Oldes

make/rebol3.nest

@@ -886,4 +886,20 @@ eggs: [
 			shared:   %lib-rebol3-core-x64-osx
 		]
 	]
+	"Test extension 32bit" [
+		name:  %test-x86.rebx
+		files: only %tests/extension/test.c
+		:arch-x86
+		compiler: gcc
+		flags: [-O2 shared]
+		#if Linux? [ flag: -fPIC ]
+	]
+	"Test extension 64bit" [
+		name:  %test-x64.rebx
+		files: only %tests/extension/test.c
+		:arch-x64
+		compiler: gcc
+		flags: [-O2 shared]
+		#if Linux? [ flag: -fPIC ]
+	]
 ]

src/core/f-extension.c

@@ -449,6 +449,8 @@ x*/	int Do_Callback(REBSER *obj, u32 name, RXIARG *args, RXIARG *result)
 	REBCNT n;
 	RXIFRM frm;	// args stored here
 
+	CLEARS(&frm);
+
 	// All of these were checked above on definition:
 	val = BLK_HEAD(VAL_FUNC_BODY(value));
 	cmd = (int)VAL_INT64(val+1);
@@ -485,6 +487,7 @@ x*/	int Do_Callback(REBSER *obj, u32 name, RXIARG *args, RXIARG *result)
 	case RXR_FALSE:
 		SET_FALSE(val);
 		break;
+	case RXR_BAD_ARGS:
 	case RXR_ERROR:
 		{
 			const char* errmsg = frm.args[1].series;

src/tests/extension/test.c

@@ -0,0 +1,47 @@
+#include "reb-host.h"
+#include "host-lib.h"
+//#include <stdio.h> 
+
+RL_LIB *RL; // Link back to reb-lib from embedded extensions
+
+const char *init_block =
+    "REBOL [\n"
+        "Title: {Add two integers}\n"
+        "Type: module\n"
+        "Exports: [addi ]\n" // exporting just the first command!
+    "]\n"
+    "addi:  command [i1 [integer!] i2 [integer!]]\n"
+    "addi2: command [i1 [integer!] i2 [integer!]]\n" // this one is not exported
+    "bad-args: command [{generic error}]\n"
+    "error: command [{throws an error with text}]\n"
+;
+
+RXIEXT const char *RX_Init(int opts, RL_LIB *lib) {
+    RL = lib;
+    //printf("RXinit %llu %llu\n", sizeof(REBREQ) , sizeof(REBEVT));
+    if (!CHECK_STRUCT_ALIGN) return 0;
+    return init_block;
+}
+
+RXIEXT int RX_Quit(int opts) {
+    return 0;
+}
+
+RXIEXT int RX_Call(int cmd, RXIFRM *frm, void *ctx) {
+    //printf("RX_Call cmd: %i\n", cmd);
+    switch(cmd) {
+        case 0: 
+            RXA_INT64(frm,1) = RXA_INT64(frm, 1) + RXA_INT64(frm, 2);
+            break;
+        case 1:
+            RXA_INT64(frm,1) = 2 * (RXA_INT64(frm, 1) + RXA_INT64(frm, 2));
+            break;
+        case 2:
+            return RXR_BAD_ARGS; //https://github.com/Oldes/Rebol-issues/issues/1867
+        case 3:
+            RXA_SERIES(frm,1) = "test error!";
+            return RXR_ERROR;
+
+    }
+    return RXR_VALUE;
+}