diff --git a/rapx/src/analysis/core/alias_analysis/default/alias.rs b/rapx/src/analysis/core/alias_analysis/default/alias.rs
index 02cd3d71..b8aad0c3 100644
--- a/rapx/src/analysis/core/alias_analysis/default/alias.rs
+++ b/rapx/src/analysis/core/alias_analysis/default/alias.rs
@@ -584,8 +584,6 @@ impl<'tcx> MopGraph<'tcx> {
 }
 
 pub fn is_no_alias_intrinsic(def_id: DefId) -> bool {
-    if def_id == call_mut() || def_id == clone() || def_id == take() {
-        return true;
-    }
-    return false;
+    let v = [call_mut_opt(), clone_opt(), take_opt()];
+    contains(&v, def_id)
 }
diff --git a/rapx/src/analysis/core/alias_analysis/default/graph.rs b/rapx/src/analysis/core/alias_analysis/default/graph.rs
index f8daa2a0..2bb20c70 100644
--- a/rapx/src/analysis/core/alias_analysis/default/graph.rs
+++ b/rapx/src/analysis/core/alias_analysis/default/graph.rs
@@ -423,13 +423,7 @@ impl<'tcx> MopGraph<'tcx> {
                 } => {
                     if let Operand::Constant(c) = func {
                         if let &ty::FnDef(id, ..) = c.ty().kind() {
-                            // for no_std crates without using alloc,
-                            // dealloc will be never found, thus call dealloc_opt here
-                            if id == drop()
-                                || id == drop_in_place()
-                                || id == manually_drop()
-                                || dealloc_opt().map(|f| f == id).unwrap_or(false)
-                            {
+                            if is_drop_fn(id) {
                                 cur_bb.terminator = Term::Drop(terminator.clone());
                             } else {
                                 cur_bb.terminator = Term::Call(terminator.clone());
diff --git a/rapx/src/analysis/core/alias_analysis/default/mod.rs b/rapx/src/analysis/core/alias_analysis/default/mod.rs
index 9f29b56a..f0036cb9 100644
--- a/rapx/src/analysis/core/alias_analysis/default/mod.rs
+++ b/rapx/src/analysis/core/alias_analysis/default/mod.rs
@@ -233,14 +233,14 @@ impl<'tcx> AliasAnalyzer<'tcx> {
 
     fn handle_conor_cases(&mut self) {
         let cases = [
-            copy_from_nonoverlapping(),
-            copy_to_nonoverlapping(),
-            copy_to(),
-            copy_from(),
+            copy_from_nonoverlapping_opt(),
+            copy_to_nonoverlapping_opt(),
+            copy_to_opt(),
+            copy_from_opt(),
         ];
         let alias = MopAliasPair::new(1, true, true, 2, true, true);
         for (key, value) in self.fn_map.iter_mut() {
-            if cases.iter().any(|lock| lock == key) {
+            if contains(&cases, *key) {
                 value.alias_set.clear();
                 value.alias_set.insert(alias.clone());
             }
diff --git a/rapx/src/analysis/utils/fn_info.rs b/rapx/src/analysis/utils/fn_info.rs
index 32c0eb13..032d673a 100644
--- a/rapx/src/analysis/utils/fn_info.rs
+++ b/rapx/src/analysis/utils/fn_info.rs
@@ -1418,16 +1418,11 @@ pub fn generate_mir_cfg_dot<'tcx>(
                     is_drop_related = true;
                 }
                 TerminatorKind::Call { func, .. } => {
-                    if let Operand::Constant(c) = func {
-                        if let ty::FnDef(def_id, _) = *c.ty().kind() {
-                            if def_id == drop()
-                                || def_id == drop_in_place()
-                                || def_id == manually_drop()
-                                || dealloc_opt().map(|f| f == def_id).unwrap_or(false)
-                            {
-                                is_drop_related = true;
-                            }
-                        }
+                    if let Operand::Constant(c) = func
+                        && let ty::FnDef(def_id, _) = *c.ty().kind()
+                        && is_drop_fn(def_id)
+                    {
+                        is_drop_related = true;
                     }
                 }
                 _ => {}
diff --git a/rapx/src/def_id.rs b/rapx/src/def_id.rs
index 72a4bed9..c927c86d 100644
--- a/rapx/src/def_id.rs
+++ b/rapx/src/def_id.rs
@@ -79,12 +79,16 @@ macro_rules! intrinsics {
     ($( $id:ident : $paths:expr ,)+ ) => {
         const INTRINSICS: &[&[&str]] = &[$( $paths ,)+];
         $(
-            pub fn $id() -> DefId {
-                ${concat($id, _opt)} ().unwrap_or_else(||
-                    panic!("Failed to retrieve the DefId of {:#?}.", $paths)
-                )
-            }
+            // Retrieved the fn DefId. Panic if the fn doesn't exist.
+            // pub fn $id() -> DefId {
+            //     ${concat($id, _opt)} ().unwrap_or_else(||
+            //         panic!("Failed to retrieve the DefId of {:#?}.", $paths)
+            //     )
+            // }
 
+            // Retrieved the fn DefId. Returns None if the fn doesn't exist.
+            // This is preferred especially RAPx is used to compile nostd crates or build-std,
+            // where the fn is likely absent.
             pub fn ${concat($id, _opt)} () -> Option<DefId> {
                 let map = &INIT.get().expect("Intrinsics DefIds haven't been initialized.").map;
                 for path in $paths {
@@ -168,3 +172,20 @@ intrinsics! {
 pub fn to_internal<T: CrateDef>(val: &T, tcx: TyCtxt) -> DefId {
     rustc_internal::internal(tcx, val.def_id())
 }
+
+/// Find any drop fn. Any of these drop fns can be missing, e.g. for crates like no_std without
+/// using alloc, dealloc doesn't exist.
+pub fn is_drop_fn(target: DefId) -> bool {
+    let drop_fn = [
+        drop_opt(),
+        drop_in_place_opt(),
+        manually_drop_opt(),
+        dealloc_opt(),
+    ];
+    contains(&drop_fn, target)
+}
+
+/// Is the targe DefId in the given array.
+pub fn contains(v: &[Option<DefId>], target: DefId) -> bool {
+    v.contains(&Some(target))
+}
diff --git a/rapx/src/lib.rs b/rapx/src/lib.rs
index 01d05d1f..29c7466b 100644
--- a/rapx/src/lib.rs
+++ b/rapx/src/lib.rs
@@ -145,11 +145,18 @@ impl Callbacks for RapCallback {
 
     fn after_crate_root_parsing(
         &mut self,
-        _compiler: &interface::Compiler,
+        compiler: &interface::Compiler,
         krate: &mut ast::Crate,
     ) -> Compilation {
-        preprocess::dummy_fns::create_dummy_fns(krate);
-        preprocess::ssa_preprocess::create_ssa_struct(krate);
+        let build_std = compiler
+            .sess
+            .opts
+            .crate_name
+            .as_deref()
+            .map(|s| matches!(s, "core" | "std"))
+            .unwrap_or(false);
+        preprocess::dummy_fns::create_dummy_fns(krate, build_std);
+        preprocess::ssa_preprocess::create_ssa_struct(krate, build_std);
         Compilation::Continue
     }
     fn after_analysis<'tcx>(&mut self, _compiler: &Compiler, tcx: TyCtxt<'tcx>) -> Compilation {
diff --git a/rapx/src/preprocess/dummy_fns.rs b/rapx/src/preprocess/dummy_fns.rs
index 2a1145a0..26d04e2d 100644
--- a/rapx/src/preprocess/dummy_fns.rs
+++ b/rapx/src/preprocess/dummy_fns.rs
@@ -1,4 +1,4 @@
-use super::doc_attr;
+use super::set_attrs;
 use rustc_ast::*;
 use rustc_span::{DUMMY_SP, symbol::Ident};
 use thin_vec::ThinVec;
@@ -31,7 +31,7 @@ fn make_dummy_block() -> Block {
     }
 }
 
-fn make_dummy_fn(ident_name: &str) -> Box<Item> {
+fn make_dummy_fn(ident_name: &str, build_std: bool) -> Box<Item> {
     let ident = Ident::from_str(ident_name);
 
     let fn_ast = Fn {
@@ -45,7 +45,7 @@ fn make_dummy_fn(ident_name: &str) -> Box<Item> {
     };
 
     Box::new(Item {
-        attrs: ThinVec::from([doc_attr()]),
+        attrs: set_attrs(build_std),
         id: DUMMY_NODE_ID,
         kind: ItemKind::Fn(Box::new(fn_ast)),
         vis: Visibility {
@@ -58,8 +58,8 @@ fn make_dummy_fn(ident_name: &str) -> Box<Item> {
     })
 }
 
-pub(crate) fn create_dummy_fns(krate: &mut Crate) {
-    let raw_ptr_fn = make_dummy_fn("__raw_ptr_deref_dummy");
+pub(crate) fn create_dummy_fns(krate: &mut Crate, build_std: bool) {
+    let raw_ptr_fn = make_dummy_fn("__raw_ptr_deref_dummy", build_std);
     //let static_mut_fn = make_dummy_fn("__static_mut_deref_dummy");
 
     krate.items.push(raw_ptr_fn);
diff --git a/rapx/src/preprocess/mod.rs b/rapx/src/preprocess/mod.rs
index 00a8592b..6803b43c 100644
--- a/rapx/src/preprocess/mod.rs
+++ b/rapx/src/preprocess/mod.rs
@@ -1,12 +1,17 @@
 pub mod dummy_fns;
 pub mod ssa_preprocess;
 
-use rustc_ast::{token::CommentKind, *};
-use rustc_span::{DUMMY_SP, symbol::Symbol};
+use rustc_ast::{
+    token::{CommentKind, Delimiter, Lit, Token, TokenKind},
+    tokenstream::{DelimSpan, Spacing, TokenStream, TokenTree},
+    *,
+};
+use rustc_span::{DUMMY_SP, Ident, symbol::Symbol};
+use thin_vec::ThinVec;
 
 /// Empty `#[doc]` on the struct.
 /// cc https://github.com/Artisan-Lab/RAPx/issues/184
-pub fn doc_attr() -> Attribute {
+fn doc_attr() -> Attribute {
     Attribute {
         kind: AttrKind::DocComment(CommentKind::Line, Symbol::intern("doc")),
         id: AttrId::ZERO,
@@ -14,3 +19,46 @@ pub fn doc_attr() -> Attribute {
         span: DUMMY_SP,
     }
 }
+
+// #[stable(feature = "foo", since = "1.93")]
+fn stability_attr() -> Attribute {
+    let mut attr = NormalAttr::from_ident(Ident::from_str("stable"));
+    let tokens: Vec<_> = {
+        let feature = Token::from_ast_ident(Ident::from_str("feature"));
+        let eq = Token::new(TokenKind::Eq, DUMMY_SP);
+        let feature_val = Token::new(
+            TokenKind::Literal(Lit::new(token::LitKind::Str, Symbol::intern("foo"), None)),
+            DUMMY_SP,
+        );
+        let comma = Token::new(TokenKind::Comma, DUMMY_SP);
+        let since = Token::from_ast_ident(Ident::from_str("since"));
+        let since_val = Token::new(
+            TokenKind::Literal(Lit::new(token::LitKind::Str, Symbol::intern("1.93"), None)),
+            DUMMY_SP,
+        );
+        [feature, eq, feature_val, comma, since, eq, since_val]
+            .into_iter()
+            .map(|t| TokenTree::Token(t, Spacing::Alone))
+            .collect()
+    };
+    attr.item.args = AttrArgs::Delimited(DelimArgs {
+        dspan: DelimSpan::dummy(),
+        delim: Delimiter::Parenthesis,
+        tokens: TokenStream::new(tokens),
+    });
+    Attribute {
+        kind: AttrKind::Normal(attr.into()),
+        id: AttrId::ZERO,
+        style: AttrStyle::Outer,
+        span: DUMMY_SP,
+    }
+}
+
+fn set_attrs(build_std: bool) -> ThinVec<Attribute> {
+    let mut v = ThinVec::with_capacity(2);
+    v.push(doc_attr());
+    if build_std {
+        v.push(stability_attr());
+    }
+    v
+}
diff --git a/rapx/src/preprocess/ssa_preprocess.rs b/rapx/src/preprocess/ssa_preprocess.rs
index 76e407c8..93a88f93 100644
--- a/rapx/src/preprocess/ssa_preprocess.rs
+++ b/rapx/src/preprocess/ssa_preprocess.rs
@@ -1,4 +1,4 @@
-use super::doc_attr;
+use super::set_attrs;
 use rustc_ast::*;
 use rustc_span::{
     DUMMY_SP,
@@ -6,7 +6,7 @@ use rustc_span::{
 };
 use thin_vec::ThinVec;
 
-pub(crate) fn create_ssa_struct(_krate: &mut Crate) {
+pub(crate) fn create_ssa_struct(_krate: &mut Crate, build_std: bool) {
     rap_debug!("[CALLBACK] Injecting new structs into the AST...");
 
     let ssa_struct = create_struct(
@@ -23,6 +23,7 @@ pub(crate) fn create_ssa_struct(_krate: &mut Crate) {
             ("para9", Symbol::intern("i128")),
             ("para10", Symbol::intern("i128")),
         ],
+        build_std,
     );
 
     let essa_struct = create_struct(
@@ -32,6 +33,7 @@ pub(crate) fn create_ssa_struct(_krate: &mut Crate) {
             ("op2", Symbol::intern("i128")),
             ("cmp", Symbol::intern("i128")),
         ],
+        build_std,
     );
 
     _krate.items.push(ssa_struct);
@@ -39,11 +41,15 @@ pub(crate) fn create_ssa_struct(_krate: &mut Crate) {
 
     // println!("[CALLBACK] Injection complete. Continuing compilation...");
 }
-pub(crate) fn create_struct(name: &str, fields_def: Vec<(&str, Symbol)>) -> Box<Item> {
+pub(crate) fn create_struct(
+    name: &str,
+    fields_def: Vec<(&str, Symbol)>,
+    build_std: bool,
+) -> Box<Item> {
     let fields: ThinVec<FieldDef> = fields_def
         .into_iter()
         .map(|(fname, fty)| FieldDef {
-            attrs: ThinVec::from([doc_attr()]),
+            attrs: set_attrs(build_std),
             vis: Visibility {
                 span: DUMMY_SP,
                 kind: VisibilityKind::Public,
@@ -76,7 +82,7 @@ pub(crate) fn create_struct(name: &str, fields_def: Vec<(&str, Symbol)>) -> Box<
     let item_kind = ItemKind::Struct(ident, Generics::default(), variant_data);
 
     Box::new(Item {
-        attrs: ThinVec::from([doc_attr()]),
+        attrs: set_attrs(build_std),
         id: NodeId::from_u32(0),
         kind: item_kind,
         vis: Visibility {