Fix Windows extension feature detection

Author: samuel-williams-shopify

.github/workflows/test.yaml

@@ -16,6 +16,7 @@ jobs:
         os:
           - ubuntu
           - macos
+          - windows
 
         ruby:
           - "3.3"

ext/extconf.rb

@@ -27,7 +27,7 @@
 	$LDFLAGS << " -fsanitize=address -fsanitize=undefined"
 end
 
-have_func("rb_tracearg_instruction_sequence", "ruby/debug.h")
+have_func("rb_tracearg_instruction_sequence((rb_trace_arg_t *)0)", "ruby/debug.h")
 
 create_header
 

ext/ruby/coverage/tracer.c

@@ -291,9 +291,6 @@ static void Ruby_Coverage_Tracer_on_line(VALUE data, const rb_trace_arg_t *trace
 
 static VALUE Ruby_Coverage_Tracer_start(VALUE self)
 {
-	struct Ruby_Coverage_Tracer *tracer;
-	TypedData_Get_Struct(self, struct Ruby_Coverage_Tracer, &Ruby_Coverage_Tracer_type, tracer);
-
 	#ifdef HAVE_RB_TRACEARG_INSTRUCTION_SEQUENCE
 	rb_add_event_hook2(
 		(rb_event_hook_func_t)Ruby_Coverage_Tracer_on_script_compiled,
@@ -302,6 +299,9 @@ static VALUE Ruby_Coverage_Tracer_start(VALUE self)
 		RUBY_EVENT_HOOK_FLAG_SAFE | RUBY_EVENT_HOOK_FLAG_RAW_ARG
 	);
 	#else
+	struct Ruby_Coverage_Tracer *tracer;
+	TypedData_Get_Struct(self, struct Ruby_Coverage_Tracer, &Ruby_Coverage_Tracer_type, tracer);
+
 	if (NIL_P(tracer->script_compiled_tracepoint)) {
 		RB_OBJ_WRITE(self, &tracer->script_compiled_tracepoint,
 			rb_tracepoint_new(Qnil, RUBY_EVENT_SCRIPT_COMPILED,

releases.md

@@ -1,5 +1,9 @@
 # Releases
 
+## Unreleased
+
+  - Fix native extension builds on Windows when `rb_tracearg_instruction_sequence` is not declared by Ruby's public headers, and avoid an unused variable compiler warning.
+
 ## v0.1.1
 
   - Fix an unused variable compiler warning in the native extension.