Guard against most egregious mistakes in calling the library

LuaJIT FFI is not inherently memory safe and there is no way
to completely guard against the caller doing something that
will trample over memory, but we can get pretty close. Biggest
issue is that an empty table will stand-in for a ref struct with
a null ref. So check for that in all the calls. In the calls that
raise errors we now have a specific error for it. In the other
functions the "nil" object is handled quietly but without a nullptr
dereference and hopefully no UB.

.luarc.json

@@ -8,5 +8,6 @@
     "lua_modules/share/lua/5.1/?.lua",
     "lua_modules/share/lua/5.1/?/init.lua"
   ],
+  "workspace.library": ["${3rd}/busted/library", "${3rd}/luassert/library"],
   "workspace.checkThirdParty": false
 }

Makefile

@@ -1,22 +1,29 @@
-SRCDIR ?= .
+SRCDIR := .
-CC ?= $(CROSS)gcc
+CC := $(CROSS)gcc
-CFLAGS ?= -fPIC -O2
+CFLAGS := -fPIC -O2
 CFLAGS += -Wall -I$(SRCDIR)/kiwi
-LIBFLAG ?= -shared
+LIBFLAG := -shared
-LIB_EXT ?= so
+LIB_EXT := so
 
 ifeq ($(findstring gcc, $(CC)), gcc)
   CXX := $(subst gcc, g++, $(CC))
-  CXXFLAGS += -std=c++11
+  CXXFLAGS += -std=c++14
+  ifneq ($(SANITIZE),)
+    CFLAGS += -fsanitize=undefined -fsanitize=address
+  endif
 else
 ifeq ($(CC), clang)
   CXX := clang++
-  CXXFLAGS += -std=c++11
+  CXXFLAGS += -std=c++14
+  ifneq ($(SANITIZE),)
+    CFLAGS += -fsanitize=undefined -fsanitize=address
+  endif
 else
   CXX := $(CC)
 endif
 endif
 
+
 all: ckiwi.$(LIB_EXT)
 
 install:
@@ -26,7 +33,7 @@ install:
 clean:
 	rm -f ckiwi.$(LIB_EXT)
 
-ckiwi.$(LIB_EXT): $(SRCDIR)/ckiwi/ckiwi.cpp
+ckiwi.$(LIB_EXT): $(SRCDIR)/ckiwi/ckiwi.cpp $(SRCDIR)/ckiwi/ckiwi.h
 	$(CXX) $(CXXFLAGS) $(CFLAGS) -fPIC -Wall -I$(SRCDIR)/kiwi $(LIBFLAG) -o $@ $<
 
 .PHONY: all install clean

README.md

@@ -11,7 +11,7 @@ Cassowary constraint solving is a technique that is particularly well suited to
 
 There are a few Lua implementations or attempts. The SILE typesetting system has a pure Lua implementation of the original Cassowary code, which appears to be correct but is quite slow. There are two extant Lua ports of Kiwi, one that is based on a C rewrite of Kiwi. However testing of these was not encouraging with either segfaults or incorrect results.
 Since the C++ Kiwi library is well tested and widely used it was simpler to provide a LuaJIT FFI wrapper and use that.
-This package has no dependencies other than a C++11 toolchain to compile the included Kiwi library and a small C wrapper.
+This package has no dependencies other than a C++14 toolchain to compile the included Kiwi library and a small C wrapper.
 
 The Lua API has a pure Lua expression builder. There is of course some overhead to this, however in most cases expression building is infrequent and the underlying structures can be reused.
 

ckiwi/.clang-format

@@ -27,7 +27,7 @@ BreakBeforeTernaryOperators: true
 BreakConstructorInitializers: AfterColon
 BreakInheritanceList: AfterColon
 BreakStringLiterals: false
-ColumnLimit: 90
+ColumnLimit: 98
 CompactNamespaces: false
 ConstructorInitializerAllOnOneLineOrOnePerLine: true
 ConstructorInitializerIndentWidth: 4

ckiwi/ckiwi.cpp

@@ -2,104 +2,206 @@
 
 #include <kiwi/kiwi.h>
 
+#include <cstdlib>
 #include <cstring>
 
 using namespace kiwi;
 
 namespace {
-template<class T, class CS>
+
-class alignas(T) SharedRef {
+template<typename T, typename R, typename... Args>
+inline R to_cref(Args&&... args) {
+   static_assert(
+       sizeof(R) >= sizeof(T),  //NOLINT(bugprone-sizeof-expression)
+       "to_cref: R too small for T"
+   );
+   static_assert(alignof(R) >= alignof(T), "to_cref: R alignment too small for T");
+
+   R cref;
+   new (&cref) T(std::forward<Args>(args)...);
+   return cref;
+}
+
+template<typename... Args>
+inline decltype(auto) to_var_cref(Args&&... args) {
+   return to_cref<Variable, KiwiVarRef>(std::forward<Args>(args)...);
+}
+
+template<typename... Args>
+inline decltype(auto) to_constraint_cref(Args&&... args) {
+   return to_cref<Constraint, KiwiConstraintRef>(std::forward<Args>(args)...);
+}
+
+template<class T, class R>
+class SharedRef {
  private:
-   CS ref_;
+   R& cref_;
 
  public:
-   T* operator&() {
+   explicit SharedRef<T, R>(R& cref) : cref_(cref) {}
-      return reinterpret_cast<T*>(&ref_);
+
+   static_assert(
+       sizeof(R) >= sizeof(T),  //NOLINT(bugprone-sizeof-expression)
+       "SharedRef<T,CS> CS too small for T"
+   );
+
+   void destroy() {
+      if (cref_) {
+         ptr()->~T();
+         cref_ = nullptr;
+      }
+   }
+
+   T* ptr() {
+      T* p;
+      void* s = &cref_;
+      std::memcpy(&p, &s, sizeof p);  //NOLINT(bugprone-sizeof-expression)
+      return p;
+   }
+
+   const T* const_ptr() const {
+      const T* p;
+      const void* s = &cref_;
+      std::memcpy(&p, &s, sizeof p);  //NOLINT(bugprone-sizeof-expression)
+      return p;
+   }
+
+   const T& cref() const {
+      return *const_ptr();
+   }
+
+   T* operator&() const {
+      return ptr();
    }
 
    T* operator->() {
-      return reinterpret_cast<T*>(&ref_);
+      return ptr();
    }
 
-   operator T&() {
+   const T* operator->() const {
-      return *reinterpret_cast<T*>(&ref_);
+      return const_ptr();
    }
 
-   operator CS() const {
+   operator const T&() const {
-      return ref_;
+      return cref();
    }
 
-   T& instance() {
+   explicit operator bool() const {
-      return *reinterpret_cast<T*>(&ref_);
+      return cref_;
    }
-
-   void destroy() {
-      instance().~T();
-      ref_ = {0};
-   }
-
-   SharedRef<T, CS>(CS ref) : ref_(ref) {}
-
-   template<typename... Args>
-   SharedRef<T, CS>(Args&&... args) {
-      new (&ref_) T(std::forward<Args>(args)...);
-   }
-
-   static_assert(sizeof(CS) >= sizeof(T), "SharedRef cannot wrap T (size)");
 };
 
 using ConstraintRef = SharedRef<Constraint, KiwiConstraintRef>;
 using VariableRef = SharedRef<Variable, KiwiVarRef>;
+using ConstVariableRef = const SharedRef<const Variable, const KiwiVarRef>;
 
-KiwiErr make_error(KiwiErrKind kind, const std::exception& ex) {
+KiwiErrPtr new_error(KiwiErrPtr base, const std::exception& ex) {
-   constexpr auto max_n = sizeof(KiwiErr::message) - 1;
+   if (!std::strcmp(ex.what(), base->message))
-   const auto n = std::min(std::strlen(ex.what()), max_n);
+      return base;
 
-   KiwiErr err {kind};
+   const auto msg_n = std::strlen(ex.what()) + 1;
 
-   std::memcpy(err.message, ex.what(), n);
+   auto* mem = static_cast<char*>(std::malloc(sizeof(KiwiErr) + msg_n));
-   if (n == max_n)
+   if (!mem) {
-      err.message[max_n] = 0;
+      return base;
+   }
+
+   const auto* err = new (mem) KiwiErr {base->kind, mem + sizeof(KiwiErr), true};
+   std::memcpy(const_cast<char*>(err->message), ex.what(), msg_n);
    return err;
 }
 
-KiwiErr make_error(KiwiErrKind kind) {
+static const constexpr KiwiErr kKiwiErrUnhandledCxxException {
-   return KiwiErr {kind, {0}};
+    KiwiErrUnknown,
-}
+    "An unhandled C++ exception occurred."};
+
+static const constexpr KiwiErr kKiwiErrNullObjectArg0 {
+    KiwiErrNullObject,
+    "null object passed as argument #0 (self)"};
+
+static const constexpr KiwiErr kKiwiErrNullObjectArg1 {
+    KiwiErrNullObject,
+    "null object passed as argument #1"};
 
 template<typename F>
-inline KiwiErr wrap_err(F&& f) {
+inline KiwiErrPtr wrap_err(F&& f) {
    try {
       f();
-   } catch (const UnsatisfiableConstraint& err) {
+   } catch (const UnsatisfiableConstraint& ex) {
-      return make_error(KiwiErrUnsatisfiableConstraint, err);
+      static const constexpr KiwiErr err {
-   } catch (const UnknownConstraint& err) {
+          KiwiErrUnsatisfiableConstraint,
-      return make_error(KiwiErrUnknownConstraint, err);
+          "The constraint cannot be satisfied."};
-   } catch (const DuplicateConstraint& err) {
+      return &err;
-      return make_error(KiwiErrDuplicateConstraint, err);
+   } catch (const UnknownConstraint& ex) {
-   } catch (const UnknownEditVariable& err) {
+      static const constexpr KiwiErr err {
-      return make_error(KiwiErrUnknownEditVariable, err);
+          KiwiErrUnknownConstraint,
-   } catch (const DuplicateEditVariable& err) {
+          "The constraint has not been added to the solver."};
-      return make_error(KiwiErrDuplicateEditVariable, err);
+      return &err;
-   } catch (const BadRequiredStrength& err) {
+
-      return make_error(KiwiErrBadRequiredStrength, err);
+   } catch (const DuplicateConstraint& ex) {
-   } catch (const InternalSolverError& err) {
+      static const constexpr KiwiErr err {
-      return make_error(KiwiErrInternalSolverError, err);
+          KiwiErrDuplicateConstraint,
+          "The constraint has already been added to the solver."};
+      return &err;
+
+   } catch (const UnknownEditVariable& ex) {
+      static const constexpr KiwiErr err {
+          KiwiErrUnknownEditVariable,
+          "The edit variable has not been added to the solver."};
+      return &err;
+
+   } catch (const DuplicateEditVariable& ex) {
+      static const constexpr KiwiErr err {
+          KiwiErrDuplicateEditVariable,
+          "The edit variable has already been added to the solver."};
+      return &err;
+
+   } catch (const BadRequiredStrength& ex) {
+      static const constexpr KiwiErr err {
+          KiwiErrBadRequiredStrength,
+          "A required strength cannot be used in this context."};
+      return &err;
+
+   } catch (const InternalSolverError& ex) {
+      static const constexpr KiwiErr base {
+          KiwiErrInternalSolverError,
+          "An internal solver error occurred."};
+      return new_error(&base, ex);
    } catch (std::bad_alloc&) {
-      return make_error(KiwiErrAlloc);
+      static const constexpr KiwiErr err {KiwiErrAlloc, "A memory allocation failed."};
-   } catch (const std::exception& err) {
+      return &err;
-      return make_error(KiwiErrUnknown, err);
+   } catch (const std::exception& ex) {
+      return new_error(&kKiwiErrUnhandledCxxException, ex);
    } catch (...) {
-      return make_error(KiwiErrUnknown);
+      return &kKiwiErrUnhandledCxxException;
    }
-   return make_error(KiwiErrNone);
+   return nullptr;
 }
+
+template<typename P, typename R, typename F>
+inline KiwiErrPtr wrap_err(P ptr, F&& f) {
+   if (!ptr) {
+      return &kKiwiErrNullObjectArg0;
+   }
+   return wrap_err([&]() { f(ptr); });
+}
+
+template<typename P, typename R, typename F>
+inline KiwiErrPtr wrap_err(P ptr, R ref, F&& f) {
+   if (!ptr) {
+      return &kKiwiErrNullObjectArg0;
+   } else if (!ref) {
+      return &kKiwiErrNullObjectArg1;
+   }
+   return wrap_err([&]() { f(ptr, ref); });
+}
+
 }  // namespace
 
 extern "C" {
 
 KiwiVarRef kiwi_var_new(const char* name) {
-   return VariableRef(name);
+   return to_var_cref(name ? name : "");
 }
 
 void kiwi_var_del(KiwiVarRef var) {
@@ -107,42 +209,50 @@ void kiwi_var_del(KiwiVarRef var) {
 }
 
 const char* kiwi_var_name(KiwiVarRef var) {
-   return VariableRef(var)->name().c_str();
+   const VariableRef self(var);
+   return self ? self->name().c_str() : "(<null>)";
 }
 
 void kiwi_var_set_name(KiwiVarRef var, const char* name) {
-   VariableRef(var)->setName(name);
+   VariableRef self(var);
+   if (self)
+      self->setName(name);
 }
 
 double kiwi_var_value(KiwiVarRef var) {
-   return VariableRef(var)->value();
+   const VariableRef self(var);
+   return self ? self->value() : std::numeric_limits<double>::quiet_NaN();
 }
 
 void kiwi_var_set_value(KiwiVarRef var, double value) {
-   VariableRef(var)->setValue(value);
+   VariableRef self(var);
+   if (self)
+      self->setValue(value);
 }
 
 int kiwi_var_eq(KiwiVarRef var, KiwiVarRef other) {
-   return VariableRef(var)->equals(VariableRef(other));
+   VariableRef self(var);  // const defect in upstream
+   const VariableRef other_ref(other);
+
+   return self && other_ref && self->equals(other_ref);
 }
 
-KiwiConstraintRef kiwi_constraint_new(
+KiwiConstraintRef
-    const KiwiExpression* expression,
+kiwi_constraint_new(KiwiExpressionConstPtr expression, enum KiwiRelOp op, double strength) {
-    enum KiwiRelOp op,
-    double strength
-) {
    if (strength < 0.0) {
       strength = kiwi::strength::required;
    }
    std::vector<Term> terms;
-   terms.reserve(expression->term_count);
+   if (expression) {
+      terms.reserve(expression->term_count);
 
-   for (auto* t = expression->terms; t != expression->terms + expression->term_count;
+      for (auto* t = expression->terms; t != expression->terms + expression->term_count; ++t) {
-        ++t) {
+         ConstVariableRef var(t->var);
-      terms.emplace_back(VariableRef(t->var), t->coefficient);
+         if (var)
+            terms.emplace_back(var.cref(), t->coefficient);
+      }
    }
-
+   return to_constraint_cref(
-   return ConstraintRef(
        Expression(std::move(terms), expression->constant),
        static_cast<RelationalOperator>(op),
        strength
@@ -154,23 +264,25 @@ void kiwi_constraint_del(KiwiConstraintRef constraint) {
 }
 
 double kiwi_constraint_strength(KiwiConstraintRef constraint) {
-   return ConstraintRef(constraint)->strength();
+   const ConstraintRef self(constraint);
+   return self ? self->strength() : std::numeric_limits<double>::quiet_NaN();
 }
 
 enum KiwiRelOp kiwi_constraint_op(KiwiConstraintRef constraint) {
-   return static_cast<KiwiRelOp>(ConstraintRef(constraint)->op());
+   const ConstraintRef self(constraint);
+   return self ? static_cast<KiwiRelOp>(self->op()) : KiwiRelOp::KIWI_OP_EQ;
 }
 
-int kiwi_constraint_violated(KiwiConstraintRef constraint) {
+bool kiwi_constraint_violated(KiwiConstraintRef constraint) {
-   return ConstraintRef(constraint)->violated();
+   const ConstraintRef self(constraint);
+   return self ? self->violated() : 0;
 }
 
-int kiwi_constraint_expression(
+int kiwi_constraint_expression(KiwiConstraintRef constraint, KiwiExpression* out, int out_size) {
-    KiwiConstraintRef constraint,
+   const ConstraintRef self(constraint);
-    KiwiExpression* out,
+   if (!self)
-    int out_size
+      return 0;
-) {
+   const auto& expr = self->expression();
-   const auto& expr = ConstraintRef(constraint).instance().expression();
    const auto& terms = expr.terms();
    const int n_terms = terms.size();
    if (!out || out_size < n_terms)
@@ -178,7 +290,7 @@ int kiwi_constraint_expression(
 
    auto* p = out->terms;
    for (const auto& t : terms) {
-      *p = KiwiTerm {VariableRef(t.variable()), t.coefficient()};
+      *p = KiwiTerm {to_var_cref(t.variable()), t.coefficient()};
       ++p;
    }
    out->term_count = p - out->terms;
@@ -187,71 +299,100 @@ int kiwi_constraint_expression(
    return n_terms;
 }
 
-KiwiSolverRef kiwi_solver_new() {
+KiwiSolverPtr kiwi_solver_new() {
-   return KiwiSolverRef {new (std::nothrow) Solver()};
+   return reinterpret_cast<KiwiSolverPtr>(new (std::nothrow) Solver());
 }
 
-void kiwi_solver_del(KiwiSolverRef s) {
+void kiwi_solver_del(KiwiSolverPtr sp) {
-   delete reinterpret_cast<Solver*>(s.impl_);
+   auto* solver = reinterpret_cast<Solver*>(sp);
+   if (solver)
+      delete solver;
 }
 
-KiwiErr kiwi_solver_add_constraint(KiwiSolverRef s, KiwiConstraintRef constraint) {
+KiwiErrPtr kiwi_solver_add_constraint(KiwiSolverPtr s, KiwiConstraintRef constraint) {
-   return wrap_err([=]() {
+   return wrap_err(
-      reinterpret_cast<Solver*>(s.impl_)->addConstraint(ConstraintRef(constraint));
+       reinterpret_cast<Solver*>(s),
+       ConstraintRef(constraint),
+       [](auto solver, const auto c) { solver->addConstraint(c); }
+   );
+}
+
+KiwiErrPtr kiwi_solver_remove_constraint(KiwiSolverPtr s, KiwiConstraintRef constraint) {
+   return wrap_err(
+       reinterpret_cast<Solver*>(s),
+       ConstraintRef(constraint),
+       [](auto solver, const auto c) { solver->removeConstraint(c); }
+   );
+}
+
+bool kiwi_solver_has_constraint(KiwiSolverPtr s, KiwiConstraintRef constraint) {
+   const auto* solver = reinterpret_cast<Solver*>(s);
+   ConstraintRef c(constraint);
+   if (!solver || !c)
+      return 0;
+   return solver->hasConstraint(c);
+}
+
+KiwiErrPtr kiwi_solver_add_edit_var(KiwiSolverPtr s, KiwiVarRef var, double strength) {
+   return wrap_err(
+       reinterpret_cast<Solver*>(s),
+       VariableRef(var),
+       [strength](auto solver, const auto v) { solver->addEditVariable(v, strength); }
+   );
+}
+
+KiwiErrPtr kiwi_solver_remove_edit_var(KiwiSolverPtr s, KiwiVarRef var) {
+   return wrap_err(reinterpret_cast<Solver*>(s), VariableRef(var), [](auto solver, const auto v) {
+      solver->removeEditVariable(v);
    });
 }
 
-KiwiErr kiwi_solver_remove_constraint(KiwiSolverRef s, KiwiConstraintRef constraint) {
+bool kiwi_solver_has_edit_var(KiwiSolverPtr s, KiwiVarRef var) {
-   return wrap_err([=]() {
+   const auto* solver = reinterpret_cast<Solver*>(s);
-      reinterpret_cast<Solver*>(s.impl_)->removeConstraint(ConstraintRef(constraint));
+   VariableRef v(var);
-   });
+   if (!solver || !v)
+      return 0;
+   return solver->hasEditVariable(v);
 }
 
-int kiwi_solver_has_constraint(KiwiSolverRef s, KiwiConstraintRef constraint) {
+KiwiErrPtr kiwi_solver_suggest_value(KiwiSolverPtr s, KiwiVarRef var, double value) {
-   return reinterpret_cast<Solver*>(s.impl_)->hasConstraint(ConstraintRef(constraint));
+   return wrap_err(
+       reinterpret_cast<Solver*>(s),
+       VariableRef(var),
+
+       [value](auto solver, const auto v) { solver->suggestValue(v, value); }
+   );
 }
 
-KiwiErr kiwi_solver_add_edit_var(KiwiSolverRef s, KiwiVarRef var, double strength) {
+void kiwi_solver_update_vars(KiwiSolverPtr s) {
-   return wrap_err([=]() {
+   auto* solver = reinterpret_cast<Solver*>(s);
-      reinterpret_cast<Solver*>(s.impl_)->addEditVariable(VariableRef(var), strength);
+   if (solver)
-   });
+      solver->updateVariables();
 }
 
-KiwiErr kiwi_solver_remove_edit_var(KiwiSolverRef s, KiwiVarRef var) {
+void kiwi_solver_reset(KiwiSolverPtr s) {
-   return wrap_err([=]() {
+   auto* solver = reinterpret_cast<Solver*>(s);
-      reinterpret_cast<Solver*>(s.impl_)->removeEditVariable(VariableRef(var));
+   if (solver)
-   });
+      solver->reset();
 }
 
-int kiwi_solver_has_edit_var(KiwiSolverRef s, KiwiVarRef var) {
+void kiwi_solver_dump(KiwiSolverPtr s) {
-   return reinterpret_cast<Solver*>(s.impl_)->hasEditVariable(VariableRef(var));
+   auto* solver = reinterpret_cast<Solver*>(s);
+   if (solver)
+      solver->dump();
 }
 
-KiwiErr kiwi_solver_suggest_value(KiwiSolverRef s, KiwiVarRef var, double value) {
+char* kiwi_solver_dumps(KiwiSolverPtr s) {
-   return wrap_err([=]() {
+   auto* solver = reinterpret_cast<Solver*>(s);
-      reinterpret_cast<Solver*>(s.impl_)->suggestValue(VariableRef(var), value);
+   if (!solver)
-   });
+      return nullptr;
-}
 
-void kiwi_solver_update_vars(KiwiSolverRef s) {
+   const auto str = solver->dumps();
-   reinterpret_cast<Solver*>(s.impl_)->updateVariables();
+   const auto buf_size = str.size() + 1;
-}
+   auto* buf = static_cast<char*>(std::malloc(buf_size));
-
-void kiwi_solver_reset(KiwiSolverRef s) {
-   reinterpret_cast<Solver*>(s.impl_)->reset();
-}
-
-void kiwi_solver_dump(KiwiSolverRef s) {
-   reinterpret_cast<Solver*>(s.impl_)->dump();
-}
-
-char* kiwi_solver_dumps(KiwiSolverRef s, void* (*alloc)(size_t)) {
-   const auto val = reinterpret_cast<Solver*>(s.impl_)->dumps();
-   const auto buf_size = val.size() + 1;
-   auto* buf = static_cast<char*>(alloc ? alloc(buf_size) : malloc(buf_size));
    if (!buf)
       return nullptr;
-   std::memcpy(buf, val.c_str(), val.size() + 1);
+   std::memcpy(buf, str.c_str(), str.size() + 1);
    return buf;
 }
 

ckiwi/ckiwi.h

@@ -20,38 +20,39 @@ enum KiwiErrKind {
    KiwiErrBadRequiredStrength,
    KiwiErrInternalSolverError,
    KiwiErrAlloc,
+   KiwiErrNullObject,
    KiwiErrUnknown,
 };
 
 enum KiwiRelOp { KIWI_OP_LE, KIWI_OP_GE, KIWI_OP_EQ };
 
-typedef struct {
+struct KiwiVarRefType;
-   void* private_;
+struct KiwiConstraintRefType;
-} KiwiVarRef;
 
-typedef struct {
+typedef struct KiwiVarRefType* KiwiVarRef;
+typedef struct KiwiConstraintRefType* KiwiConstraintRef;
+
+struct KiwiTerm {
    KiwiVarRef var;
    double coefficient;
-} KiwiTerm;
+};
 
-typedef struct {
+typedef struct KiwiExpression {
    double constant;
    int term_count;
-   KiwiTerm terms[1];
+   struct KiwiTerm terms[1];  // LuaJIT: struct KiwiTerm terms_[?];
-} KiwiExpression;
+}* KiwiExpressionPtr;
 
-typedef struct {
+typedef const struct KiwiExpression* KiwiExpressionConstPtr;
-   void* private_;
-} KiwiConstraintRef;
 
-typedef struct {
+typedef struct KiwiErr {
    enum KiwiErrKind kind;
-   char message[64];
+   const char* message;
-} KiwiErr;
+   bool must_free;
+} const* KiwiErrPtr;
 
-typedef struct {
+struct KiwiSolver;
-   void* impl_;
+typedef struct KiwiSolver* KiwiSolverPtr;
-} KiwiSolverRef;
 
 KiwiVarRef kiwi_var_new(const char* name);
 void kiwi_var_del(KiwiVarRef var);
@@ -67,45 +68,30 @@ void kiwi_var_set_value(KiwiVarRef var, double value);
 int kiwi_var_eq(KiwiVarRef var, KiwiVarRef other);
 
 KiwiConstraintRef
-kiwi_constraint_new(const KiwiExpression* expression, enum KiwiRelOp op, double strength);
+kiwi_constraint_new(KiwiExpressionConstPtr expression, enum KiwiRelOp op, double strength);
 void kiwi_constraint_del(KiwiConstraintRef constraint);
 
 double kiwi_constraint_strength(KiwiConstraintRef constraint);
 
 enum KiwiRelOp kiwi_constraint_op(KiwiConstraintRef constraint);
 
-int kiwi_constraint_violated(KiwiConstraintRef constraint);
+bool kiwi_constraint_violated(KiwiConstraintRef constraint);
+int kiwi_constraint_expression(KiwiConstraintRef constraint, KiwiExpressionPtr out, int out_size);
 
-int kiwi_constraint_expression(
+KiwiErrPtr kiwi_solver_add_constraint(KiwiSolverPtr sp, KiwiConstraintRef constraint);
-    KiwiConstraintRef constraint,
+KiwiErrPtr kiwi_solver_remove_constraint(KiwiSolverPtr sp, KiwiConstraintRef constraint);
-    KiwiExpression* out,
+bool kiwi_solver_has_constraint(KiwiSolverPtr sp, KiwiConstraintRef constraint);
-    int out_size
+KiwiErrPtr kiwi_solver_add_edit_var(KiwiSolverPtr sp, KiwiVarRef var, double strength);
-);
+KiwiErrPtr kiwi_solver_remove_edit_var(KiwiSolverPtr sp, KiwiVarRef var);
+bool kiwi_solver_has_edit_var(KiwiSolverPtr sp, KiwiVarRef var);
+KiwiErrPtr kiwi_solver_suggest_value(KiwiSolverPtr sp, KiwiVarRef var, double value);
+void kiwi_solver_update_vars(KiwiSolverPtr sp);
+void kiwi_solver_reset(KiwiSolverPtr sp);
+void kiwi_solver_dump(KiwiSolverPtr sp);
+char* kiwi_solver_dumps(KiwiSolverPtr sp);
 
-KiwiErr kiwi_solver_add_constraint(KiwiSolverRef s, KiwiConstraintRef constraint);
+KiwiSolverPtr kiwi_solver_new();
-
+void kiwi_solver_del(KiwiSolverPtr sp);
-KiwiErr kiwi_solver_remove_constraint(KiwiSolverRef s, KiwiConstraintRef constraint);
-
-int kiwi_solver_has_constraint(KiwiSolverRef s, KiwiConstraintRef constraint);
-
-KiwiErr kiwi_solver_add_edit_var(KiwiSolverRef s, KiwiVarRef var, double strength);
-
-KiwiErr kiwi_solver_remove_edit_var(KiwiSolverRef s, KiwiVarRef var);
-
-int kiwi_solver_has_edit_var(KiwiSolverRef s, KiwiVarRef var);
-
-KiwiErr kiwi_solver_suggest_value(KiwiSolverRef s, KiwiVarRef var, double value);
-
-void kiwi_solver_update_vars(KiwiSolverRef s);
-
-void kiwi_solver_reset(KiwiSolverRef s);
-
-void kiwi_solver_dump(KiwiSolverRef s);
-
-char* kiwi_solver_dumps(KiwiSolverRef s, void* (*alloc)(size_t));
-
-KiwiSolverRef kiwi_solver_new();
-void kiwi_solver_del(KiwiSolverRef s);
 // LuaJIT end
 
 #ifdef __cplusplus

kiwi.lua

@@ -22,86 +22,85 @@ enum KiwiErrKind {
    KiwiErrBadRequiredStrength,
    KiwiErrInternalSolverError,
    KiwiErrAlloc,
+   KiwiErrNullObject,
    KiwiErrUnknown,
 };
 
 enum KiwiRelOp { LE, GE, EQ };
 
-typedef struct {
+struct KiwiVarRefType;
-   void* private_;
+struct KiwiConstraintRefType;
-} KiwiVarRef;
 
-typedef struct {
+typedef struct KiwiVarRefType* KiwiVarRef;
+typedef struct KiwiConstraintRefType* KiwiConstraintRef;
+
+struct KiwiTerm {
    KiwiVarRef var;
    double coefficient;
-} KiwiTerm;
+};
 
-typedef struct {
+typedef struct KiwiExpression {
    double constant;
    int term_count;
-   KiwiTerm terms_[?];
+   struct KiwiTerm terms_[?];
-} KiwiExpression;
+}* KiwiExpressionPtr;
 
-typedef struct {
+typedef const struct KiwiExpression* KiwiExpressionConstPtr;
-   void* private_;
-} KiwiConstraintRef;
 
-typedef struct {
+typedef struct KiwiErr {
    enum KiwiErrKind kind;
-   char message[64];
+   const char* message;
-} KiwiErr;
+   bool must_free;
+} const* KiwiErrPtr;
 
-typedef struct {
+struct KiwiSolver;
-   void* impl_;
+typedef struct KiwiSolver* KiwiSolverPtr;
-} KiwiSolverRef;
 
 KiwiVarRef kiwi_var_new(const char* name);
 void kiwi_var_del(KiwiVarRef var);
 
 const char* kiwi_var_name(KiwiVarRef var);
+
 void kiwi_var_set_name(KiwiVarRef var, const char* name);
+
 double kiwi_var_value(KiwiVarRef var);
+
 void kiwi_var_set_value(KiwiVarRef var, double value);
+
 int kiwi_var_eq(KiwiVarRef var, KiwiVarRef other);
 
 KiwiConstraintRef
-kiwi_constraint_new(const KiwiExpression* expression, enum KiwiRelOp op, double strength);
+kiwi_constraint_new(KiwiExpressionConstPtr expression, enum KiwiRelOp op, double strength);
 void kiwi_constraint_del(KiwiConstraintRef constraint);
 
 double kiwi_constraint_strength(KiwiConstraintRef constraint);
 
 enum KiwiRelOp kiwi_constraint_op(KiwiConstraintRef constraint);
 
-int kiwi_constraint_violated(KiwiConstraintRef constraint);
+bool kiwi_constraint_violated(KiwiConstraintRef constraint);
+int kiwi_constraint_expression(KiwiConstraintRef constraint, KiwiExpressionPtr out, int out_size);
 
-int kiwi_constraint_expression(
+KiwiErrPtr kiwi_solver_add_constraint(KiwiSolverPtr sp, KiwiConstraintRef constraint);
-    KiwiConstraintRef constraint,
+KiwiErrPtr kiwi_solver_remove_constraint(KiwiSolverPtr sp, KiwiConstraintRef constraint);
-    KiwiExpression* out,
+bool kiwi_solver_has_constraint(KiwiSolverPtr sp, KiwiConstraintRef constraint);
-    int out_size
+KiwiErrPtr kiwi_solver_add_edit_var(KiwiSolverPtr sp, KiwiVarRef var, double strength);
-);
+KiwiErrPtr kiwi_solver_remove_edit_var(KiwiSolverPtr sp, KiwiVarRef var);
+bool kiwi_solver_has_edit_var(KiwiSolverPtr sp, KiwiVarRef var);
+KiwiErrPtr kiwi_solver_suggest_value(KiwiSolverPtr sp, KiwiVarRef var, double value);
+void kiwi_solver_update_vars(KiwiSolverPtr sp);
+void kiwi_solver_reset(KiwiSolverPtr sp);
+void kiwi_solver_dump(KiwiSolverPtr sp);
+char* kiwi_solver_dumps(KiwiSolverPtr sp);
 
-KiwiErr kiwi_solver_add_constraint(KiwiSolverRef s, KiwiConstraintRef constraint);
+KiwiSolverPtr kiwi_solver_new();
-KiwiErr kiwi_solver_remove_constraint(KiwiSolverRef s, KiwiConstraintRef constraint);
+void kiwi_solver_del(KiwiSolverPtr sp);
-int kiwi_solver_has_constraint(KiwiSolverRef s, KiwiConstraintRef constraint);
-KiwiErr kiwi_solver_add_edit_var(KiwiSolverRef s, KiwiVarRef var, double strength);
-KiwiErr kiwi_solver_remove_edit_var(KiwiSolverRef s, KiwiVarRef var);
-int kiwi_solver_has_edit_var(KiwiSolverRef s, KiwiVarRef var);
-KiwiErr kiwi_solver_suggest_value(KiwiSolverRef s, KiwiVarRef var, double value);
-void kiwi_solver_update_vars(KiwiSolverRef s);
-void kiwi_solver_reset(KiwiSolverRef s);
-void kiwi_solver_dump(KiwiSolverRef s);
-
-char* kiwi_solver_dumps(KiwiSolverRef s, void* (*alloc)(size_t));
-
-KiwiSolverRef kiwi_solver_new();
-void kiwi_solver_del(KiwiSolverRef s);
 
 void free(void *);
 ]])
 
 local strformat = string.format
-local ffi_cast, ffi_copy, ffi_istype, ffi_new, ffi_sizeof, ffi_string =
+local ffi_cast, ffi_copy, ffi_gc, ffi_istype, ffi_new, ffi_string =
-   ffi.cast, ffi.copy, ffi.istype, ffi.new, ffi.sizeof, ffi.string
+   ffi.cast, ffi.copy, ffi.gc, ffi.istype, ffi.new, ffi.string
 
 local concat = table.concat
 local has_table_new, new_tab = pcall(require, "table.new")
@@ -121,13 +120,10 @@ end
 ---| '"KiwiErrBadRequiredStrength"' # The given strength is >= required.
 ---| '"KiwiErrInternalSolverError"' # An internal solver error occurred.
 ---| '"KiwiErrAlloc"' # A memory allocation error occurred.
+---| '"KiwiErrNullObject"' # A method was invoked on a null or empty object.
 ---| '"KiwiErrUnknown"' # An unknown error occurred.
 kiwi.ErrKind = ffi.typeof("enum KiwiErrKind") --[[@as kiwi.ErrKind]]
 
----@class kiwi.KiwiErr: ffi.ctype*
----@field package kind kiwi.ErrKind
----@field package message ffi.cdata*
-
 ---@alias kiwi.RelOp
 ---| '"LE"' # <= (less than or equal)
 ---| '"GE"' # >= (greater than or equal)
@@ -156,18 +152,21 @@ function kiwi.Strength.create(a, b, c, w)
    return clamp(a * w) * 1000000.0 + clamp(b * w) * 1000.0 + clamp(c * w)
 end
 
-local Var = ffi.typeof("KiwiVarRef") --[[@as kiwi.Var]]
+local Var = ffi.typeof("struct KiwiVarRefType") --[[@as kiwi.Var]]
 kiwi.Var = Var
 
-local Term = ffi.typeof("KiwiTerm") --[[@as kiwi.Term]]
+local Term = ffi.typeof("struct KiwiTerm") --[[@as kiwi.Term]]
 kiwi.Term = Term
 
-local Expression = ffi.typeof("KiwiExpression") --[[@as kiwi.Expression]]
+local Expression = ffi.typeof("struct KiwiExpression") --[[@as kiwi.Expression]]
 kiwi.Expression = Expression
 
-local Constraint = ffi.typeof("KiwiConstraintRef") --[[@as kiwi.Constraint]]
+local Constraint = ffi.typeof("struct KiwiConstraintRefType") --[[@as kiwi.Constraint]]
 kiwi.Constraint = Constraint
 
+-- JIT compiler NYI: bad argument type if ffi.sizeof is used with a structure member
+local SIZEOF_TERM = ffi.sizeof(Term)
+
 --- Define a constraint with expressions as `a <= b`.
 ---@param a kiwi.Expression|kiwi.Term|kiwi.Var|number
 ---@param b kiwi.Expression|kiwi.Term|kiwi.Var|number
@@ -199,8 +198,10 @@ end
 ---@param term kiwi.Term
 ---@nodiscard
 local function add_expr_term(expr, term)
-   local ret = ffi_new(Expression, expr.term_count + 1, expr.constant, expr.term_count + 1) --[[@as kiwi.Expression]]
+   local ret = ffi_new(Expression, expr.term_count + 1) --[[@as kiwi.Expression]]
-   ffi_copy(ret.terms_, expr.terms_, ffi_sizeof(expr.terms_, expr.term_count)) ---@diagnostic disable-line: param-type-mismatch
+   ret.constant = expr.constant
+   ret.term_count = expr.term_count + 1
+   ffi_copy(ret.terms_, expr.terms_, SIZEOF_TERM * expr.term_count) ---@diagnostic disable-line: param-type-mismatch
    ret.terms_[expr.term_count] = term
    return ret
 end
@@ -209,7 +210,9 @@ end
 ---@param term kiwi.Term
 ---@nodiscard
 local function new_expr_one(constant, term)
-   local ret = ffi_new(Expression, 1, constant, 1) --[[@as kiwi.Expression]]
+   local ret = ffi_new(Expression, 1) --[[@as kiwi.Expression]]
+   ret.constant = constant
+   ret.term_count = 1
    ret.terms_[0] = term
    return ret
 end
@@ -219,7 +222,9 @@ end
 ---@param term2 kiwi.Term
 ---@nodiscard
 local function new_expr_pair(constant, term1, term2)
-   local ret = ffi_new(Expression, 2, constant, 2) --[[@as kiwi.Expression]]
+   local ret = ffi_new(Expression, 2) --[[@as kiwi.Expression]]
+   ret.constant = constant
+   ret.term_count = 2
    ret.terms_[0] = term1
    ret.terms_[1] = term2
    return ret
@@ -266,10 +271,9 @@ end
 
 ffi.metatype(Var, {
    __index = Var_cls,
-   __gc = ckiwi.kiwi_var_del,
 
    __new = function(_, name)
-      return ckiwi.kiwi_var_new(name)
+      return ffi_gc(ckiwi.kiwi_var_new(name), ckiwi.kiwi_var_del)
    end,
 
    __mul = function(a, b)
@@ -393,7 +397,8 @@ ffi.metatype(Term, {
    end,
 
    __tostring = function(term)
-      return tostring(term.coefficient) .. " " .. term.var:name()
+      return tostring(term.var:name())
+      --return tostring(term.coefficient) .. " " .. term.var:name()
    end,
 })
 
@@ -419,8 +424,8 @@ do
          a.constant + b.constant,
          a.term_count + b.term_count
       ) --[[@as kiwi.Expression]]
-      ffi_copy(ret.terms_, a.terms_, ffi_sizeof(a.terms_, a.term_count)) ---@diagnostic disable-line: param-type-mismatch
+      ffi_copy(ret.terms_, a.terms_, SIZEOF_TERM * a.term_count) ---@diagnostic disable-line: param-type-mismatch
-      ffi_copy(ret.terms_[a.term_count], b.terms_, ffi_sizeof(b.terms_, b.term_count)) ---@diagnostic disable-line: param-type-mismatch
+      ffi_copy(ret.terms_[a.term_count], b.terms_, SIZEOF_TERM * b.term_count) ---@diagnostic disable-line: param-type-mismatch
       return ret
    end
 
@@ -428,8 +433,11 @@ do
    ---@param constant number
    ---@nodiscard
    local function new_expr_constant(expr, constant)
-      local ret = ffi_new(Expression, expr.term_count, constant, expr.term_count) --[[@as kiwi.Expression]]
+      local ret = ffi_new(Expression, expr.term_count) --[[@as kiwi.Expression]]
-      ffi_copy(ret.terms_, expr.terms_, ffi_sizeof(expr.terms_, expr.term_count)) ---@diagnostic disable-line: param-type-mismatch
+      ret.constant = constant
+      ret.term_count = expr.term_count
+
+      ffi_copy(ret.terms_, expr.terms_, SIZEOF_TERM * expr.term_count) ---@diagnostic disable-line: param-type-mismatch
       return ret
    end
 
@@ -577,6 +585,7 @@ end
 ---@return kiwi.Constraint
 ---@nodiscard
 function kiwi.new_pair_ratio_constraint(left, coeff, right, constant, op, strength)
+   assert(ffi_istype(Var, left) and ffi_istype(Var, right))
    return Constraint(
       new_expr_pair(-(constant or 0.0), Term(left), Term(right, -coeff)),
       op,
@@ -594,6 +603,7 @@ end
 ---@return kiwi.Constraint
 ---@nodiscard
 function kiwi.new_pair_constraint(left, right, constant, op, strength)
+   assert(ffi_istype(Var, left) and ffi_istype(Var, right))
    return Constraint(
       new_expr_pair(-(constant or 0.0), Term(left), Term(right, -1.0)),
       op,
@@ -610,6 +620,7 @@ end
 ---@return kiwi.Constraint
 ---@nodiscard
 function kiwi.new_single_constraint(var, constant, op, strength)
+   assert(ffi_istype(Var, var))
    return Constraint(new_expr_one(-(constant or 0.0), Term(var)), op, strength)
 end
 
@@ -618,10 +629,12 @@ local REQUIRED = Strength.REQUIRED
 
 ffi.metatype(Constraint, {
    __index = Constraint_cls,
-   __gc = ckiwi.kiwi_constraint_del,
 
    __new = function(_, expr, op, strength)
-      return ckiwi.kiwi_constraint_new(expr, op or "EQ", strength or REQUIRED)
+      return ffi_gc(
+         ckiwi.kiwi_constraint_new(expr, op or "EQ", strength or REQUIRED),
+         ckiwi.kiwi_constraint_del
+      )
    end,
 
    __tostring = function(self)
@@ -670,19 +683,42 @@ local function new_error(kind, message, solver, item)
    }, Error_mt)
 end
 
----@param f fun(solver: kiwi.Solver, item: any, ...): kiwi.KiwiErr
+local C = ffi.C
+
+---@class kiwi.KiwiErr: ffi.ctype*
+---@field package kind kiwi.ErrKind
+---@field package message ffi.cdata*
+---@field package must_free boolean
+---@overload fun(): kiwi.KiwiErr
+local KiwiErr = ffi.typeof("struct KiwiErr") --[[@as kiwi.KiwiErr]]
+--
+---@param f fun(solver: kiwi.Solver, item: any, ...): kiwi.KiwiErr?
 ---@param solver kiwi.Solver
 ---@param item any
 local function try_solver(f, solver, item, ...)
    local err = f(solver, item, ...)
-   if err.kind ~= 0 then
+   if err ~= nil then
-      error(new_error(err.kind, ffi_string(err.message), solver, item))
+      local kind = err.kind
+      local message = err.message ~= nil and ffi_string(err.message) or ""
+      if err.must_free then
+         print("FEEE")
+         C.free(err)
+      end
+      error(new_error(kind, message, solver, item))
    end
 end
 
 ---@class kiwi.Solver: ffi.ctype*
 ---@overload fun(): kiwi.Solver
 local Solver_cls = {
+   --- Test whether a constraint is in the solver.
+   ---@type fun(self: kiwi.Solver, constraint: kiwi.Constraint): boolean
+   has_constraint = ckiwi.kiwi_solver_has_constraint,
+
+   --- Test whether an edit variable has been added to the solver.
+   ---@type fun(self: kiwi.Solver, var: kiwi.Var): boolean
+   has_edit_var = ckiwi.kiwi_solver_has_edit_var,
+
    --- Update the values of the external solver variables.
    ---@type fun(self: kiwi.Solver)
    update_vars = ckiwi.kiwi_solver_update_vars,
@@ -719,14 +755,6 @@ function Solver_cls:remove_constraint(constraint)
    try_solver(ckiwi.kiwi_solver_remove_constraint, self, constraint)
 end
 
---- Test whether a constraint is in the solver.
----@param constraint kiwi.Constraint
----@return boolean
----@nodiscard
-function Solver_cls:has_constraint(constraint)
-   return ckiwi.kiwi_solver_has_constraint(self, constraint) ~= 0
-end
-
 --- Adds an edit variable to the solver.
 ---
 --- This method should be called before the `suggestValue` method is
@@ -748,14 +776,6 @@ function Solver_cls:remove_edit_var(var)
    try_solver(ckiwi.kiwi_solver_remove_edit_var, self, var)
 end
 
---- Test whether an edit variable has been added to the solver.
----@param var kiwi.Var the edit variable to check
----@return boolean
----@nodiscard
-function Solver_cls:has_edit_var(var)
-   return ckiwi.kiwi_solver_has_edit_var(self, var) ~= 0
-end
-
 --- Suggest a value for the given edit variable.
 --- This method should be used after an edit variable has been added to the solver in order
 --- to suggest the value for that variable. After all suggestions have been made,
@@ -772,18 +792,17 @@ end
 ---@return string
 ---@nodiscard
 function Solver_cls:dumps()
-   local cs = ckiwi.kiwi_solver_dumps(self, nil)
+   local cs = ckiwi.kiwi_solver_dumps(self)
    local s = ffi_string(cs)
-   ffi.C.free(cs)
+   C.free(cs)
    return s
 end
 
-kiwi.Solver = ffi.metatype("KiwiSolverRef", {
+kiwi.Solver = ffi.metatype("struct KiwiSolver", {
    __index = Solver_cls,
    __new = function(_)
-      return ckiwi.kiwi_solver_new()
+      return ffi_gc(ckiwi.kiwi_solver_new(), ckiwi.kiwi_solver_del)
    end,
-   __gc = ckiwi.kiwi_solver_del,
 
    __tostring = function(self)
       return strformat("kiwi.Solver(0x%X)", ffi_cast("intptr_t", ffi_cast("void*", self)))

ljkiwi-scm-1.rockspec

@@ -29,5 +29,6 @@ build = {
    install_variables = {
       INST_LIBDIR = "$(LIBDIR)",
       INST_LUADIR = "$(LUADIR)",
+      LIB_EXT = "$(LIB_EXTENSION)",
    },
 }