Made it easier to support 0-size structs in the future.

src/cc65/compile.c

@@ -218,14 +218,16 @@ static void Parse (void)
                     ** void types in ISO modes.
                     */
                     if (Size == 0) {
-                        if (!IsTypeVoid (Decl.Type)) {
+                        if (!IsEmptiableObjectType (Decl.Type)) {
                             if (!IsTypeArray (Decl.Type)) {
                                 /* Size is unknown and not an array */
-                                Error ("Variable '%s' has unknown size", Decl.Ident);
+                                Error ("Cannot initialize variable '%s' of unknown size", Decl.Ident);
                             }
                         } else if (IS_Get (&Standard) != STD_CC65) {
                             /* We cannot declare variables of type void */
-                            Error ("Illegal type for variable '%s'", Decl.Ident);
+                            Error ("Illegal type '%s' for variable '%s'",
+                                   GetFullTypeName (Decl.Type),
+                                   Decl.Ident);
                         }
                     }
 
@@ -253,7 +255,7 @@ static void Parse (void)
                         /* We cannot declare variables of type void */
                         Error ("Illegal type for variable '%s'", Decl.Ident);
                         Entry->Flags &= ~(SC_STORAGE | SC_DEF);
-                    } else if (Size == 0 && SymIsDef (Entry)) {
+                    } else if (Size == 0 && SymIsDef (Entry) && !IsEmptiableObjectType (Decl.Type)) {
                         /* Size is unknown. Is it an array? */
                         if (!IsTypeArray (Decl.Type)) {
                             Error ("Variable '%s' has unknown size", Decl.Ident);

src/cc65/datatype.c

@@ -805,7 +805,11 @@ unsigned CheckedSizeOf (const Type* T)
 {
     unsigned Size = SizeOf (T);
     if (Size == 0) {
+        if (HasUnknownSize (T + 1)) {
             Error ("Size of type '%s' is unknown", GetFullTypeName (T));
+        } else {
+            Error ("Size of type '%s' is 0", GetFullTypeName (T));
+        }
         Size = SIZEOF_CHAR;     /* Don't return zero */
     }
     return Size;
@@ -821,7 +825,11 @@ unsigned CheckedPSizeOf (const Type* T)
 {
     unsigned Size = PSizeOf (T);
     if (Size == 0) {
-        Error ("Size of type '%s' is unknown", GetFullTypeName (T + 1));
+        if (HasUnknownSize (T + 1)) {
+            Error ("Pointer to type '%s' of unknown size", GetFullTypeName (T + 1));
+        } else {
+            Error ("Pointer to type '%s' of 0 size", GetFullTypeName (T + 1));
+        }
         Size = SIZEOF_CHAR;     /* Don't return zero */
     }
     return Size;

src/cc65/locals.c

@@ -174,8 +174,8 @@ static void ParseRegisterDecl (Declaration* Decl, int Reg)
         Sym->Flags |= SC_REF;
     }
 
-    /* Cannot allocate a variable of zero size */
+    /* Cannot allocate a variable of unknown size */
-    if (Size == 0) {
+    if (HasUnknownSize (Sym->Type)) {
         if (IsTypeArray (Decl->Type)) {
             Error ("Array '%s' has unknown size", Decl->Ident);
         } else {
@@ -370,8 +370,8 @@ static void ParseAutoDecl (Declaration* Decl)
         }
     }
 
-    /* Cannot allocate a variable of zero size */
+    /* Cannot allocate an incomplete variable */
-    if (Size == 0) {
+    if (HasUnknownSize (Sym->Type)) {
         if (IsTypeArray (Decl->Type)) {
             Error ("Array '%s' has unknown size", Decl->Ident);
         } else {
@@ -428,8 +428,8 @@ static void ParseStaticDecl (Declaration* Decl)
 
     }
 
-    /* Cannot allocate a variable of zero size */
+    /* Cannot allocate an incomplete variable */
-    if (Size == 0) {
+    if (HasUnknownSize (Sym->Type)) {
         if (IsTypeArray (Decl->Type)) {
             Error ("Array '%s' has unknown size", Decl->Ident);
         } else {