Exports symbols to be shared with external GDB/JIT debugging interfac… (

#3373)

* Exports symbols to be shared with external GDB/JIT debugging interface tools.
Windows O/S specific requirement.

* Moved comments into platform specific compiler directive sections.

crates/runtime/src/helpers.c

@@ -61,14 +61,16 @@ void wasmtime_longjmp(void *JmpBuf) {
   platform_longjmp(*buf, 1);
 }
 
-// Just in case cross-language LTO is enabled we set the `noinline` attribute
-// and also try to have some sort of side effect in this function with a dummy
-// `asm` statement.
-//
-// Note the `weak` linkage here, though, which is intended to let other code
-// override this symbol if it's defined elsewhere, since this definition doesn't
-// matter.
-#ifndef CFG_TARGET_OS_windows
+#ifdef CFG_TARGET_OS_windows
+  // export required for external access.
+__declspec(dllexport)
+#else
+  // Note the `weak` linkage here, though, which is intended to let other code
+  // override this symbol if it's defined elsewhere, since this definition doesn't
+  // matter.
+  // Just in case cross-language LTO is enabled we set the `noinline` attribute
+  // and also try to have some sort of side effect in this function with a dummy
+  // `asm` statement.
 __attribute__((weak, noinline))
 #endif
 void __jit_debug_register_code() {
@@ -84,14 +86,19 @@ struct JITDescriptor {
   void* first_entry_;
 };
 
-// Note the `weak` linkage here which is the same purpose as above. We want to
-// let other runtimes be able to override this since our own definition isn't
-// important.
-#ifndef CFG_TARGET_OS_windows
-__attribute__((weak))
+#ifdef CFG_TARGET_OS_windows
+  // export required for external access.
+  __declspec(dllexport) 
+#else
+  // Note the `weak` linkage here which is the same purpose as above. We want to
+  // let other runtimes be able to override this since our own definition isn't
+  // important.
+  __attribute__((weak))
 #endif
 struct JITDescriptor __jit_debug_descriptor = {1, 0, NULL, NULL};
 
+
+
 struct JITDescriptor* wasmtime_jit_debug_descriptor() {
   return &__jit_debug_descriptor;
 }