make thread safety a compile-time toggle

include/cubescript/cubescript_conf.hh

@@ -23,6 +23,18 @@
 #  include <span>
 #endif
 
+#ifndef LIBCUBESCRIPT_CONF_THREAD_SAFE
+/** @brief Controls thread safety of the implementation.
+ *
+ * By default, libcubescript is thread safe. That means using locking where
+ * necessary as well as atomic variables where necessary. If you do not need
+ * that, you can disable this by overriding this macro to 0 in your user
+ * configuration. This does not make any difference in behavior when used
+ * in single-threaded scenarios, other than possibly better performance.
+ */
+#define LIBCUBESCRIPT_CONF_THREAD_SAFE 1
+#endif
+
 namespace cubescript {
 #if !defined(LIBCUBESCRIPT_CONF_USER_INTEGER)
     /** @brief The integer type used.

src/cs_ident.cc

@@ -12,14 +12,14 @@ namespace cubescript {
 
 template<typename T>
 static inline T var_load(unsigned char const *base) noexcept {
-    std::atomic<T> const *p{};
+    atomic_type<T> const *p{};
     std::memcpy(&p, &base, sizeof(void *));
     return p->load();
 }
 
 template<typename T>
 static inline void var_store(unsigned char *base, T v) noexcept {
-    std::atomic<T> *p{};
+    atomic_type<T> *p{};
     std::memcpy(&p, &base, sizeof(void *));
     p->store(v);
 }
@@ -29,24 +29,24 @@ static inline void var_store(unsigned char *base, T v) noexcept {
  */
 
 var_value::var_value(integer_type v): p_type{value_type::INTEGER} {
-    new (p_stor) std::atomic<integer_type>{v};
-    new (p_ostor) std::atomic<integer_type>{0};
+    new (p_stor) atomic_type<integer_type>{v};
+    new (p_ostor) atomic_type<integer_type>{0};
 }
 
 var_value::var_value(float_type v): p_type{value_type::FLOAT} {
     FS vs{};
     std::memcpy(&vs, &v, sizeof(v));
-    new (p_stor) std::atomic<FS>{vs};
-    new (p_ostor) std::atomic<FS>{0};
+    new (p_stor) atomic_type<FS>{vs};
+    new (p_ostor) atomic_type<FS>{0};
 }
 
 var_value::var_value(std::string_view const &v, state &cs):
     p_type{value_type::STRING}
 {
-    new (p_stor) std::atomic<char const *>{
+    new (p_stor) atomic_type<char const *>{
         state_p{cs}.ts().istate->strman->add(v)
     };
-    new (p_ostor) std::atomic<char const *>{nullptr};
+    new (p_ostor) atomic_type<char const *>{nullptr};
 }
 
 var_value::~var_value() {

src/cs_ident.hh

@@ -3,8 +3,9 @@
 
 #include <cubescript/cubescript.hh>
 
+#include "cs_lock.hh"
+
 #include <bitset>
-#include <atomic>
 #include <memory>
 
 namespace cubescript {
@@ -46,9 +47,9 @@ struct var_value {
 
 private:
     using VU = union {
-        std::atomic<integer_type> i;
-        std::atomic<FS> f;
-        std::atomic<char const *> s;
+        atomic_type<integer_type> i;
+        atomic_type<FS> f;
+        atomic_type<char const *> s;
     };
 
     /* fixed upon creation */

src/cs_lock.hh

@@ -0,0 +1,54 @@
+#ifndef LIBCUBESCRIPT_LOCK_HH
+#define LIBCUBESCRIPT_LOCK_HH
+
+#include <cubescript/cubescript.hh>
+
+#if LIBCUBESCRIPT_CONF_THREAD_SAFE
+#include <mutex>
+#include <atomic>
+#endif
+
+namespace cubescript {
+
+#if ! LIBCUBESCRIPT_CONF_THREAD_SAFE
+
+struct mutex_type {
+    void lock() {}
+    void unlock() {}
+};
+
+template<typename T>
+struct atomic_type {
+    T p_v;
+
+    T load() const {
+        return p_v;
+    }
+    void store(T v) {
+        p_v = v;
+    }
+};
+
+#else
+
+using mutex_type = std::mutex;
+template<typename T>
+using atomic_type = std::atomic<T>;
+
+#endif
+
+struct mtx_guard {
+    mtx_guard(mutex_type &m): p_m{m} {
+        m.lock();
+    }
+
+    ~mtx_guard() {
+        p_m.unlock();
+    }
+
+    mutex_type &p_m;
+};
+
+} /* namespace cubescript */
+
+#endif

src/cs_state.cc

@@ -9,6 +9,7 @@
 #include "cs_vm.hh"
 #include "cs_parser.hh"
 #include "cs_error.hh"
+#include "cs_lock.hh"
 
 namespace cubescript {
 
@@ -48,7 +49,7 @@ ident *internal_state::lookup_ident(std::size_t idx) {
     if (idx < MAX_ARGUMENTS) {
         return argmap[idx];
     }
-    std::lock_guard<std::mutex> l{ident_mtx};
+    mtx_guard l{ident_mtx};
     return identmap[idx];
 }
 
@@ -56,12 +57,12 @@ ident const *internal_state::lookup_ident(std::size_t idx) const {
     if (idx < MAX_ARGUMENTS) {
         return argmap[idx];
     }
-    std::lock_guard<std::mutex> l{ident_mtx};
+    mtx_guard l{ident_mtx};
     return identmap[idx];
 }
 
 std::size_t internal_state::get_identnum() const {
-    std::lock_guard<std::mutex> l{ident_mtx};
+    mtx_guard l{ident_mtx};
     return identmap.size();
 }
 
@@ -70,7 +71,7 @@ void internal_state::foreach_ident(void (*f)(ident *, void *), void *data) {
     for (std::size_t i = 0; i < nids; ++i) {
         ident *id;
         {
-            std::lock_guard<std::mutex> l{ident_mtx};
+            mtx_guard l{ident_mtx};
             id = identmap[i];
         }
         f(id, data);
@@ -83,7 +84,7 @@ ident *internal_state::add_ident(ident *id, ident_impl *impl) {
     }
     ident_p{*id}.impl(impl);
     {
-        std::lock_guard<std::mutex> l{ident_mtx};
+        mtx_guard l{ident_mtx};
         idents[id->name()] = id;
         impl->p_index = int(identmap.size());
         identmap.push_back(id);
@@ -108,7 +109,7 @@ ident &internal_state::new_ident(state &cs, std::string_view name, int flags) {
 }
 
 ident *internal_state::get_ident(std::string_view name) const {
-    std::lock_guard<std::mutex> l{ident_mtx};
+    mtx_guard l{ident_mtx};
     auto id = idents.find(name);
     if (id == idents.end()) {
         return nullptr;

src/cs_state.hh

@@ -7,10 +7,10 @@
 #include <string>
 #include <vector>
 #include <array>
-#include <mutex>
 
 #include "cs_bcode.hh"
 #include "cs_ident.hh"
+#include "cs_lock.hh"
 
 namespace cubescript {
 
@@ -52,7 +52,7 @@ struct internal_state {
     > idents;
     std::vector<ident *, std_allocator<ident *>> identmap;
     std::array<ident *, MAX_ARGUMENTS> argmap;
-    mutable std::mutex ident_mtx;
+    mutable mutex_type ident_mtx;
 
     string_pool *strman;
     empty_block *empty;

src/cs_strman.cc

@@ -4,6 +4,7 @@
 
 #include "cs_strman.hh"
 #include "cs_thread.hh"
+#include "cs_lock.hh"
 
 namespace cubescript {
 
@@ -21,7 +22,7 @@ inline string_ref_state *get_ref_state(char const *ptr) {
 
 char const *string_pool::add(std::string_view str) {
     {
-        std::lock_guard<std::mutex> l{p_mtx};
+        mtx_guard l{p_mtx};
         auto it = counts.find(str);
         /* already present: just increment ref */
         if (it != counts.end()) {
@@ -43,7 +44,7 @@ char const *string_pool::add(std::string_view str) {
     memcpy(strp, str.data(), ss);
     /* store it */
     {
-        std::lock_guard<std::mutex> l{p_mtx};
+        mtx_guard l{p_mtx};
         counts.emplace(std::string_view{strp, ss}, get_ref_state(strp));
     }
     return strp;
@@ -52,7 +53,7 @@ char const *string_pool::add(std::string_view str) {
 char const *string_pool::internal_ref(char const *ptr) {
     auto *ss = get_ref_state(ptr);
     {
-        std::lock_guard<std::mutex> l{p_mtx};
+        mtx_guard l{p_mtx};
         ++ss->refcount;
     }
     return ptr;
@@ -63,7 +64,7 @@ string_ref string_pool::steal(char *ptr) {
     auto sr = std::string_view{ptr, ss->length};
     string_ref_state *st = nullptr;
     {
-        std::lock_guard<std::mutex> l{p_mtx};
+        mtx_guard l{p_mtx};
         /* much like add(), but we already have memory */
         auto it = counts.find(sr);
         if (it != counts.end()) {
@@ -78,7 +79,7 @@ string_ref string_pool::steal(char *ptr) {
         std::memcpy(&rp, &st, sizeof(rp));
         return string_ref{rp};
     } else {
-        std::lock_guard<std::mutex> l{p_mtx};
+        mtx_guard l{p_mtx};
         ss->refcount = 0; /* string_ref will increment it */
         counts.emplace(sr, ss);
     }
@@ -87,7 +88,7 @@ string_ref string_pool::steal(char *ptr) {
 
 void string_pool::internal_unref(char const *ptr) {
     auto *ss = get_ref_state(ptr);
-    if (std::lock_guard<std::mutex> l{p_mtx}; !--ss->refcount) {
+    if (mtx_guard l{p_mtx}; !--ss->refcount) {
         /* refcount zero, so ditch it
          * this path is a little slow...
          */
@@ -113,7 +114,7 @@ void string_pool::internal_unref(char const *ptr) {
 char const *string_pool::find(std::string_view str) const {
     string_ref_state *sp;
     {
-        std::lock_guard<std::mutex> l{p_mtx};
+        mtx_guard l{p_mtx};
         auto it = counts.find(str);
         if (it == counts.end()) {
             return nullptr;

src/cs_strman.hh

@@ -5,10 +5,10 @@
 
 #include <unordered_map>
 #include <string_view>
-#include <mutex>
 
 #include "cs_std.hh"
 #include "cs_state.hh"
+#include "cs_lock.hh"
 
 namespace cubescript {
 
@@ -83,7 +83,7 @@ struct string_pool {
     char *alloc_buf(std::size_t len) const;
 
     internal_state *cstate;
-    mutable std::mutex p_mtx{};
+    mutable mutex_type p_mtx{};
     std::unordered_map<
         std::string_view, string_ref_state *,
         std::hash<std::string_view>,