From 1def48cf7604801abd87e81da8e806e070c1b060 Mon Sep 17 00:00:00 2001
From: Daniel Kolesa <daniel@octaforge.org>
Date: Tue, 30 Mar 2021 20:37:50 +0200
Subject: [PATCH] redo alias_stack for robustness (guarantee order of push/pop)

---
 include/cubescript/cubescript.hh | 10 ++----
 src/cs_ident.cc                  | 52 ++++++++------------------------
 src/lib_base.cc                  |  8 ++---
 3 files changed, 20 insertions(+), 50 deletions(-)

diff --git a/include/cubescript/cubescript.hh b/include/cubescript/cubescript.hh
index 3ea5eb6..56afcf0 100644
--- a/include/cubescript/cubescript.hh
+++ b/include/cubescript/cubescript.hh
@@ -826,19 +826,15 @@ struct LIBCUBESCRIPT_EXPORT alias_stack {
     alias_stack &operator=(alias_stack const &) = delete;
     alias_stack &operator=(alias_stack &&v) = delete;
 
-    bool set_alias(ident *id);
-    alias *get_alias() const noexcept;
-    bool has_alias() const noexcept;
+    alias *get_alias() noexcept { return p_alias; }
+    alias const *get_alias() const noexcept { return p_alias; }
 
-    bool push(any_value val);
-    bool pop();
+    bool set(any_value val);
 
     explicit operator bool() const noexcept;
 
 private:
-    state &p_state;
     alias *p_alias;
-    bool p_pushed;
 };
 
 struct LIBCUBESCRIPT_EXPORT stacked_value: any_value {
diff --git a/src/cs_ident.cc b/src/cs_ident.cc
index 411b4b2..a0cbf53 100644
--- a/src/cs_ident.cc
+++ b/src/cs_ident.cc
@@ -413,57 +413,31 @@ LIBCUBESCRIPT_EXPORT int command::get_num_args() const {
 
 /* external API for alias stack management */
 
-LIBCUBESCRIPT_EXPORT alias_stack::alias_stack(state &cs, ident *a):
-    p_state{cs}, p_pushed{false}
-{
-    set_alias(a);
+LIBCUBESCRIPT_EXPORT alias_stack::alias_stack(state &cs, ident *a) {
+    if (!a || !a->is_alias()) {
+        p_alias = nullptr;
+        return;
+    }
+    p_alias = static_cast<alias *>(a);
+    static_cast<alias_impl *>(p_alias)->push_arg(
+        cs.thread_pointer()->idstack.emplace_back(cs)
+    );
 }
 
 LIBCUBESCRIPT_EXPORT alias_stack::~alias_stack() {
-    pop();
+    static_cast<alias_impl *>(p_alias)->pop_arg();
 }
 
-LIBCUBESCRIPT_EXPORT bool alias_stack::set_alias(ident *id) {
-    if (!id || !id->is_alias()) {
-        return false;
-    }
-    p_alias = static_cast<alias *>(id);
-    return true;
-}
-
-LIBCUBESCRIPT_EXPORT alias *alias_stack::get_alias() const noexcept {
-    return p_alias;
-}
-
-LIBCUBESCRIPT_EXPORT bool alias_stack::has_alias() const noexcept {
-    return !!p_alias;
-}
-
-LIBCUBESCRIPT_EXPORT bool alias_stack::push(any_value val) {
+LIBCUBESCRIPT_EXPORT bool alias_stack::set(any_value val) {
     if (!p_alias) {
         return false;
     }
-    auto &ts = *p_state.thread_pointer();
-    auto &ap = *static_cast<alias_impl *>(p_alias);
-    if (!p_pushed) {
-        ap.push_arg(ts.idstack.emplace_back(p_state));
-        p_pushed = true;
-    }
-    ap.p_val = std::move(val);
-    return true;
-}
-
-LIBCUBESCRIPT_EXPORT bool alias_stack::pop() {
-    if (!p_pushed || !p_alias) {
-        return false;
-    }
-    static_cast<alias_impl *>(p_alias)->pop_arg();
-    p_pushed = false;
+    static_cast<alias_impl *>(p_alias)->p_val = std::move(val);
     return true;
 }
 
 LIBCUBESCRIPT_EXPORT alias_stack::operator bool() const noexcept {
-    return has_alias();
+    return !!p_alias;
 }
 
 } /* namespace cubescript */
diff --git a/src/lib_base.cc b/src/lib_base.cc
index 3b5658f..7958268 100644
--- a/src/lib_base.cc
+++ b/src/lib_base.cc
@@ -16,7 +16,7 @@ static inline void do_loop(
         any_value idv{cs};
         for (integer_type i = 0; i < n; ++i) {
             idv.set_int(offset + i * step);
-            st.push(idv);
+            st.set(idv);
             if (cond && !cs.run(cond).get_bool()) {
                 break;
             }
@@ -42,7 +42,7 @@ static inline void do_loop_conc(
         any_value idv{cs};
         for (integer_type i = 0; i < n; ++i) {
             idv.set_int(offset + i * step);
-            st.push(idv);
+            st.set(idv);
             any_value v{cs};
             switch (cs.run_loop(body, v)) {
                 case loop_state::BREAK:
@@ -163,7 +163,7 @@ void init_lib_base(state &gcs) {
                 return;
             }
             if (args[1].get_bool()) {
-                st.push(args[1]);
+                st.set(args[1]);
                 cs.run(args[2].get_code(), res);
             }
         }
@@ -306,7 +306,7 @@ end:
             if (st.get_alias()->get_flags() & IDENT_FLAG_ARG) {
                 return;
             }
-            st.push(args[1]);
+            st.set(args[1]);
             cs.run(args[2].get_code(), res);
         }
     });