Track current break target using a stack (#29)

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -990,6 +990,7 @@ bool Converter::VisitIfStmt(clang::IfStmt *stmt) {
 }
 
 bool Converter::VisitWhileStmt(clang::WhileStmt *stmt) {
+  PushBreakTarget push(break_target_, BreakTarget::Loop);
   StrCat("'loop_:");
   StrCat(keyword::kWhile);
   ConvertCondition(stmt->getCond());
@@ -1002,6 +1003,7 @@ bool Converter::VisitWhileStmt(clang::WhileStmt *stmt) {
 }
 
 bool Converter::VisitDoStmt(clang::DoStmt *stmt) {
+  PushBreakTarget push(break_target_, BreakTarget::Loop);
   StrCat("'loop_:");
   StrCat(keyword::kLoop, token::kOpenCurlyBracket);
   curr_for_inc_.emplace(nullptr);
@@ -1016,6 +1018,7 @@ bool Converter::VisitDoStmt(clang::DoStmt *stmt) {
 }
 
 bool Converter::VisitForStmt(clang::ForStmt *stmt) {
+  PushBreakTarget push(break_target_, BreakTarget::Loop);
   Convert(stmt->getInit());
   StrCat("'loop_:");
   StrCat(keyword::kWhile);
@@ -1055,6 +1058,7 @@ void Converter::ConvertLoopVariable(clang::VarDecl *decl,
 
 void Converter::ConvertForRangeBody(clang::CXXForRangeStmt *stmt,
                                     const clang::VarDecl *map_iter_decl) {
+  PushBreakTarget push(break_target_, BreakTarget::Loop);
   std::optional<ScopedMapIterDecl> skip;
   if (map_iter_decl)
     skip.emplace(*this, map_iter_decl);
@@ -1137,7 +1141,7 @@ bool Converter::VisitCXXForRangeStmtIndexBased(clang::CXXForRangeStmt *stmt,
 
 bool Converter::VisitBreakStmt([[maybe_unused]] clang::BreakStmt *stmt) {
   StrCat(keyword::kBreak);
-  if (break_with_explicit_label_) {
+  if (isSwitchBreak()) {
     StrCat("'switch");
   }
   return false;
@@ -2644,6 +2648,7 @@ bool Converter::VisitSwitchCase(clang::SwitchCase *stmt) {
 }
 
 bool Converter::VisitSwitchStmt(clang::SwitchStmt *stmt) {
+  PushBreakTarget push(break_target_, BreakTarget::Switch);
   StrCat("'switch: {");
   StrCat(std::format("let __match_cond = {};", ToString(stmt->getCond())));
   StrCat("match __match_cond");
@@ -2653,7 +2658,6 @@ bool Converter::VisitSwitchStmt(clang::SwitchStmt *stmt) {
   auto body = llvm::cast<clang::CompoundStmt>(stmt->getBody());
   assert(body);
 
-  break_with_explicit_label_ = true;
   for (auto it = body->body_begin(), end = body->body_end(); it != end;) {
     if (auto switch_case = clang::dyn_cast<clang::SwitchCase>(*it)) {
       if (clang::isa<clang::CaseStmt>(switch_case)) {
@@ -2676,7 +2680,6 @@ bool Converter::VisitSwitchStmt(clang::SwitchStmt *stmt) {
   if (!has_default_case) {
     StrCat(R"( _ => {})");
   }
-  break_with_explicit_label_ = false;
 
   StrCat("}");
   StrCat("}");

cpp2rust/converter/converter.h

@@ -463,10 +463,30 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
   clang::ASTContext &ctx_;
   clang::FunctionDecl *curr_function_ = nullptr;
   bool in_function_formals_ = false;
-  bool break_with_explicit_label_ = false;
   std::stack<clang::Expr *> curr_for_inc_;
   std::stack<clang::QualType> curr_init_type_;
 
+  enum class BreakTarget { Loop, Switch };
+  std::stack<BreakTarget> break_target_;
+
+  bool isSwitchBreak() const {
+    return !break_target_.empty() && break_target_.top() == BreakTarget::Switch;
+  }
+
+  class PushBreakTarget {
+  public:
+    PushBreakTarget(std::stack<BreakTarget> &stack, BreakTarget target)
+        : stack_(stack) {
+      stack_.push(target);
+    }
+    ~PushBreakTarget() { stack_.pop(); }
+    PushBreakTarget(const PushBreakTarget &) = delete;
+    PushBreakTarget &operator=(const PushBreakTarget &) = delete;
+
+  private:
+    std::stack<BreakTarget> &stack_;
+  };
+
   std::unordered_set<const clang::VarDecl *> map_iter_decls_;
 
   struct ScopedMapIterDecl {

tests/lit/lit/formats/Cpp2RustTest.py

@@ -115,6 +115,9 @@ def fail(str, code = fail_code):
         return lit.Test.XFAIL, ''
       return fail('cpp2rust failed\n' + err)
 
+    if should_not_translate:
+      return fail('expected translation-fail but cpp2rust succeeded')
+
     expected_file = self.getExpectedFile(filepath, model, fname)
     if not os.path.exists(expected_file) and not replace_expected:
       return fail('no expected file')

tests/unit/out/refcount/switch_for_in_switch_break.rs

@@ -16,7 +16,7 @@ pub fn for_in_switch_break_0(n: i32) -> i32 {
                 let i: Value<i32> = Rc::new(RefCell::new(0));
                 'loop_: while ((*i.borrow()) < 10) {
                     if ((*i.borrow()) == 3) {
-                        break 'switch;
+                        break;
                     }
                     (*r.borrow_mut()) += (*i.borrow());
                     (*i.borrow_mut()).prefix_inc();

tests/unit/out/refcount/switch_for_switch_for_break.rs

@@ -18,7 +18,7 @@ pub fn for_switch_for_break_0(n: i32) -> i32 {
                     let j: Value<i32> = Rc::new(RefCell::new(0));
                     'loop_: while ((*j.borrow()) < 10) {
                         if ((*j.borrow()) == 2) {
-                            break 'switch;
+                            break;
                         }
                         (*r.borrow_mut()) += 1;
                         (*j.borrow_mut()).prefix_inc();

tests/unit/out/refcount/switch_nested.rs

@@ -32,15 +32,15 @@ pub fn nested_0(a: i32, b: i32) -> i32 {
                     }
                 };
                 (*r.borrow_mut()) += 1;
-                break;
+                break 'switch;
             }
             v if v == 2 => {
                 (*r.borrow_mut()) = 2;
-                break;
+                break 'switch;
             }
             _ => {
                 (*r.borrow_mut()) = -1_i32;
-                break;
+                break 'switch;
             }
         }
     };

tests/unit/out/refcount/switch_while_in_switch_break.rs

@@ -16,7 +16,7 @@ pub fn while_in_switch_break_0(n: i32) -> i32 {
                 let i: Value<i32> = Rc::new(RefCell::new(0));
                 'loop_: while ((*i.borrow()) < 10) {
                     if ((*i.borrow()) == 4) {
-                        break 'switch;
+                        break;
                     }
                     (*r.borrow_mut()) += (*i.borrow());
                     (*i.borrow_mut()).prefix_inc();

tests/unit/out/unsafe/switch_for_in_switch_break.rs

@@ -15,7 +15,7 @@ pub unsafe fn for_in_switch_break_0(mut n: i32) -> i32 {
                 let mut i: i32 = 0;
                 'loop_: while ((i) < (10)) {
                     if ((i) == (3)) {
-                        break 'switch;
+                        break;
                     }
                     r += i;
                     i.prefix_inc();

tests/unit/out/unsafe/switch_for_switch_for_break.rs

@@ -17,7 +17,7 @@ pub unsafe fn for_switch_for_break_0(mut n: i32) -> i32 {
                     let mut j: i32 = 0;
                     'loop_: while ((j) < (10)) {
                         if ((j) == (2)) {
-                            break 'switch;
+                            break;
                         }
                         r += 1;
                         j.prefix_inc();

tests/unit/out/unsafe/switch_nested.rs

@@ -30,15 +30,15 @@ pub unsafe fn nested_0(mut a: i32, mut b: i32) -> i32 {
                     }
                 };
                 r += 1;
-                break;
+                break 'switch;
             }
             v if v == 2 => {
                 r = 2;
-                break;
+                break 'switch;
             }
             _ => {
                 r = -1_i32;
-                break;
+                break 'switch;
             }
         }
     };