sizeof(*(void*)) is sizeof(char)

Author: tautschnig

regression/ansi-c/sizeof5/main.c

@@ -0,0 +1,15 @@
+#define STATIC_ASSERT(condition) \
+  int some_array##__LINE__[(condition) ? 1 : -1];
+
+struct S
+{
+  int x;
+};
+
+int main()
+{
+  struct S s;
+  __typeof__(*((void *)&s.x)) *_s=&s.x;
+  STATIC_ASSERT(sizeof(*_s)==1);
+  return 0;
+}

regression/ansi-c/sizeof5/test.desc

@@ -0,0 +1,8 @@
+CORE
+main.c
+
+^EXIT=0$
+^SIGNAL=0$
+--
+^warning: ignoring
+^CONVERSION ERROR$

src/ansi-c/c_typecheck_expr.cpp

@@ -948,6 +948,12 @@ void c_typecheck_baset::typecheck_expr_sizeof(exprt &expr)
     throw 0;
   }
 
+  if(type.id()==ID_empty &&
+     expr.operands().size()==1 &&
+     expr.op0().id()==ID_dereference &&
+     expr.op0().op0().type()==pointer_type(void_type()))
+    type=char_type();
+
   exprt new_expr=size_of_expr(type, *this);
 
   if(new_expr.is_nil())