String literals are mutable in C

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -1703,6 +1703,10 @@ std::string Converter::GetEscapedStringLiteral(clang::Expr *expr,
 
 bool Converter::VisitStringLiteral(clang::StringLiteral *expr) {
   StrCat(std::format("b{}.as_ptr()", GetEscapedStringLiteral(expr, true)));
+  // In C, string literals are char[], in C++ they are const char[]
+  if (!expr->getType().isConstQualified()) {
+    StrCat(".cast_mut()");
+  }
   return false;
 }
 
@@ -1722,27 +1726,27 @@ bool Converter::VisitImplicitCastExpr(clang::ImplicitCastExpr *expr) {
     SetValueFreshness(type);
     break;
   }
-  case clang::CastKind::CK_ArrayToPointerDecay:
-    if (clang::isa<clang::StringLiteral>(sub_expr) ||
-        clang::isa<clang::PredefinedExpr>(sub_expr)) {
-      Convert(sub_expr);
-      if (IsConversionFromStringLiteralToCharPtr(expr)) {
-        StrCat(".cast_mut()");
-      }
-      return false;
-    }
+  case clang::CastKind::CK_ArrayToPointerDecay: {
     // __va_list_tag [1] decays to __va_list_tag *. Just pass through by value
     if (IsVaListType(sub_expr->getType())) {
       Convert(sub_expr);
       break;
     }
     Convert(sub_expr);
-    if (sub_expr->getType().isConstQualified()) {
-      StrCat(keyword_ptr_decay_const_);
-    } else {
-      StrCat(keyword_ptr_decay_);
+    switch (GetConstCastType(
+        expr->getType()->getPointeeType(),
+        sub_expr->getType()->getAsArrayTypeUnsafe()->getElementType())) {
+    case ConstCastType::MutableToConst:
+      StrCat(".cast_const()");
+      break;
+    case ConstCastType::ConstToMutable:
+      StrCat(".cast_mut()");
+      break;
+    default:
+      break;
     }
     break;
+  }
   case clang::CastKind::CK_BitCast: {
     PushParen paren(*this);
     Convert(sub_expr);
@@ -1756,8 +1760,19 @@ bool Converter::VisitImplicitCastExpr(clang::ImplicitCastExpr *expr) {
   }
   case clang::CastKind::CK_NoOp: {
     Convert(sub_expr);
-    if (IsConversionFromStringLiteralToCharPtr(expr)) {
-      StrCat(".cast_mut()");
+    if (expr->getType()->isPointerType() &&
+        sub_expr->getType()->isPointerType()) {
+      switch (GetConstCastType(expr->getType()->getPointeeType(),
+                               sub_expr->getType()->getPointeeType())) {
+      case ConstCastType::MutableToConst:
+        StrCat(".cast_const()");
+        break;
+      case ConstCastType::ConstToMutable:
+        StrCat(".cast_mut()");
+        break;
+      default:
+        break;
+      }
     }
     break;
   }

cpp2rust/converter/converter_lib.cpp

@@ -763,13 +763,16 @@ void Unwrap(std::string &s, std::string_view prefix, std::string_view suffix) {
   }
 }
 
-bool IsConversionFromStringLiteralToCharPtr(clang::Expr *expr) {
-  if (clang::isa<clang::StringLiteral>(expr->IgnoreImplicit()) &&
-      expr->getType()->isPointerType()) {
-    auto pointee = expr->getType()->getPointeeType();
-    return pointee->isCharType() && !pointee.isConstQualified();
+ConstCastType GetConstCastType(clang::QualType to, clang::QualType from) {
+  if (to.isConstQualified() && from.isConstQualified()) {
+    return ConstCastType::ConstToConst;
+  } else if (!to.isConstQualified() && from.isConstQualified()) {
+    return ConstCastType::ConstToMutable;
+  } else if (to.isConstQualified() && !from.isConstQualified()) {
+    return ConstCastType::MutableToConst;
+  } else {
+    return ConstCastType::MutableToMutable;
   }
-  return false;
 }
 
 } // namespace cpp2rust

cpp2rust/converter/converter_lib.h

@@ -167,6 +167,13 @@ std::vector<clang::Stmt *> GetSwitchCaseBody(clang::CompoundStmt *body,
 
 void Unwrap(std::string &s, std::string_view prefix, std::string_view suffix);
 
-bool IsConversionFromStringLiteralToCharPtr(clang::Expr *expr);
+enum class ConstCastType {
+  ConstToConst,
+  ConstToMutable,
+  MutableToConst,
+  MutableToMutable,
+};
+
+ConstCastType GetConstCastType(clang::QualType to, clang::QualType from);
 
 } // namespace cpp2rust