Use lazy initialization for statics

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -532,7 +532,10 @@ bool Converter::ConvertVarDeclSkipInit(clang::VarDecl *decl) {
   if (is_parm_with_default_value) {
     StrCat("Option<");
   }
-  Convert(qual_type);
+  {
+    PushLazyType lazy(*this, IsGlobalVar(decl) && LazyStaticInit());
+    Convert(qual_type);
+  }
   if (is_parm_with_default_value) {
     StrCat('>');
   }
@@ -597,8 +600,9 @@ void Converter::ConvertGlobalVarDecl(clang::VarDecl *decl) {
   PushConstInitializer static_init(*this, decl->isFileVarDecl() ||
                                               decl->isStaticLocal());
   StrCat(token::kAssign);
-  StrCat(keyword_unsafe_);
   {
+    PushLazyInit lazy(*this, LazyStaticInit());
+    StrCat(keyword_unsafe_);
     PushBrace push(*this);
     ConvertVarDeclInitializer(decl);
   }
@@ -2860,7 +2864,11 @@ std::string Converter::ConvertDeclRefExpr(clang::DeclRefExpr *expr) {
   }
 
   if (IsGlobalVar(expr)) {
-    return GetNamedDeclAsString(expr->getDecl());
+    if (LazyStaticInit()) {
+      return std::format("(*std::cell::LazyCell::force_mut(&mut *&raw mut {}))",
+                         GetNamedDeclAsString(decl));
+    }
+    return GetNamedDeclAsString(decl);
   }
 
   return GetNamedDeclAsString(decl);

cpp2rust/converter/converter.h

@@ -98,6 +98,7 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
   virtual bool VisitFunctionTemplateDecl(clang::FunctionTemplateDecl *decl);
 
   virtual bool VisitVarDecl(clang::VarDecl *decl);
+  virtual bool LazyStaticInit() const { return true; }
 
   void ConvertVarDecl(clang::VarDecl *decl);
 
@@ -464,7 +465,7 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
     std::string str() && { return std::move(partial_code); }
   };
 
-  template <char kOpen, char kClose> class PushDelim {
+  template <auto kOpen, auto kClose> class PushDelim {
     Converter &c;
     bool enabled;
 
@@ -489,6 +490,8 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
       PushDelim<token::kOpenCurlyBracket, token::kCloseCurlyBracket>;
   using PushParen = PushDelim<token::kOpenParen, token::kCloseParen>;
   using PushBracket = PushDelim<token::kOpenBracket, token::kCloseBracket>;
+  using PushLazyType = PushDelim<token::kLazyCellType, token::kGt>;
+  using PushLazyInit = PushDelim<token::kLazyCellNew, token::kCloseParen>;
 
   template <typename T>
   inline std::string

cpp2rust/converter/lex.h

@@ -30,6 +30,8 @@ inline constexpr char kDiv = '/';
 inline constexpr char kLt = '<';
 inline constexpr char kGt = '>';
 inline constexpr char kNewLine = '\n';
+inline constexpr const char kLazyCellType[] = "std::cell::LazyCell<";
+inline constexpr const char kLazyCellNew[] = "std::cell::LazyCell::new(||";
 } // namespace token
 
 namespace keyword {

cpp2rust/converter/models/converter_refcount.h

@@ -79,6 +79,7 @@ class ConverterRefCount final : public Converter {
   void EmitFunctionPreamble(clang::FunctionDecl *decl) override;
 
   bool VisitVarDecl(clang::VarDecl *decl) override;
+  bool LazyStaticInit() const override { return false; }
 
   void ConvertGlobalVarDecl(clang::VarDecl *decl) override;