Expose `RB_NIL_P` and `RTEST` in libcruby

These seem to be the appropriate way to check for `nil` and truthiness
of an object using the C API. I would assume that additional changes
have to happen since this touches the runtime extension, but I'm not
sure what to do.

crates/libcruby-sys/src/lib.rs

@@ -113,6 +113,12 @@ extern "C" {
     #[link_name = "HELIX_RB_TYPE_P"]
     pub fn RB_TYPE_P(val: VALUE, rb_type: isize) -> bool;
 
+    #[link_name = "HELIX_RB_NIL_P"]
+    pub fn RB_NIL_P(val: VALUE) -> bool;
+
+    #[link_name = "HELIX_RTEST"]
+    pub fn RTEST(val: VALUE) -> bool;
+
     #[link_name = "HELIX_TYPE"]
     pub fn TYPE(val: VALUE) -> isize;
 

ruby/ext/helix_runtime/native/helix_runtime.c

@@ -44,6 +44,14 @@ bool HELIX_RB_TYPE_P(VALUE v, int type) {
   return RB_TYPE_P(v, type);
 }
 
+bool HELIX_RB_NIL_P(VALUE v) {
+  return RB_NIL_P(v);
+}
+
+bool HELIX_RTEST(VALUE v) {
+  return RTEST(v);
+}
+
 VALUE HELIX_INT2FIX(int c_int) {
   return INT2FIX(c_int);
 }

ruby/ext/helix_runtime/native/helix_runtime.h

@@ -58,7 +58,9 @@ HELIX_EXTERN const void* HELIX_RARRAY_CONST_PTR(VALUE array);
 HELIX_EXTERN long HELIX_RHASH_SIZE(VALUE hash);
 
 HELIX_EXTERN bool HELIX_RB_TYPE_P(VALUE v, int type);
+HELIX_EXTERN bool HELIX_RB_NIL_P(VALUE v);
 HELIX_EXTERN int HELIX_TYPE(VALUE v);
+HELIX_EXTERN bool HELIX_RTEST(VALUE v);
 
 HELIX_EXTERN VALUE HELIX_INT2FIX(int c_int);
 HELIX_EXTERN VALUE HELIX_FIX2INT(VALUE fix);

ruby/spec/helix_runtime_spec.rb

@@ -80,6 +80,18 @@ describe HelixRuntime do
     expect(Dummy.RHASH_SIZE({a: 1, b: 2, c: 3, d: 4, e: 5})).to equal(5)
   end
 
+  it 'exports the RB_NIL_P macro' do
+    expect(Dummy.RB_NIL_P(nil)).to eq(true)
+    expect(Dummy.RB_NIL_P(:foo)).to eq(false)
+  end
+
+  it 'exports the RTEST macro' do
+    expect(Dummy.RTEST(true)).to eq(true)
+    expect(Dummy.RTEST(:foo)).to eq(true)
+    expect(Dummy.RTEST(false)).to eq(false)
+    expect(Dummy.RTEST(nil)).to eq(false)
+  end
+
   describe 'coercions' do
     it "(INT2FIX)" do
       expect(Dummy.INT2FIX(10)).to eq(10)

ruby/spec/support/dummy/ext/dummy/dummy.c

@@ -48,6 +48,16 @@ static VALUE TEST_RB_TYPE_P(VALUE _self, VALUE val, VALUE type) {
   return result ? Qtrue : Qfalse;
 }
 
+static VALUE TEST_RB_NIL_P(VALUE _self, VALUE val) {
+  int result = HELIX_RB_NIL_P(val);
+  return result ? Qtrue : Qfalse;
+}
+
+static VALUE TEST_RTEST(VALUE _self, VALUE val) {
+  int result = HELIX_RTEST(val);
+  return result ? Qtrue : Qfalse;
+}
+
 static VALUE TEST_TYPE(VALUE _self, VALUE val) {
   return INT2FIX(HELIX_TYPE(val));
 }
@@ -192,9 +202,11 @@ void Init_dummy() {
   EXPORT_RUBY_FUNC(RARRAY_CONST_PTR, 1);
   EXPORT_FUNC(RHASH_SIZE, 1);
   EXPORT_FUNC(RB_TYPE_P, 2);
+  EXPORT_FUNC(RB_NIL_P, 1);
   EXPORT_FUNC(TYPE, 1);
   EXPORT_FUNC(INT2FIX, 1);
   EXPORT_FUNC(FIX2INT, 1);
+  EXPORT_FUNC(RTEST, 1);
 
   EXPORT_FUNC(NUM2U64, 1);
   EXPORT_FUNC(U642NUM, 1);