Introduce btf::types::Enum::is_signed() method

Add the btf::types::Enum::is_signed() method exposing the fact whether
an enum is signed or not. This is similar to other existing methods such
as btf::types::Func::linkage().

Signed-off-by: Daniel Müller <deso@posteo.net>

libbpf-cargo/src/gen/btf.rs

@@ -797,15 +797,7 @@ impl<'s> GenBtf<'s> {
         };
 
         let enum_name = self.anon_types.type_name_or_anon(&t);
-
-        let mut signed = "u";
-        for value in t.iter() {
-            if value.value < 0 {
-                signed = "i";
-                break;
-            }
-        }
-
+        let signed = if t.is_signed() { "i" } else { "u" };
         let mut first_field = None;
 
         writeln!(def, r#"#[derive(Debug, Copy, Clone, Eq, PartialEq)]"#)?;

libbpf-rs/src/btf/types.rs

@@ -634,6 +634,15 @@ gen_collection_concrete_type! {
     }
 }
 
+impl Enum<'_> {
+    /// Check whether the enum is signed or not.
+    #[inline]
+    pub fn is_signed(&self) -> bool {
+        self.kind_flag()
+    }
+}
+
+
 // Fwd
 gen_fieldless_concrete_type! {
     /// A forward declared C type.