Visual Studio ignores #pragma pack on unions

Author: kroening

appveyor.yml

@@ -70,7 +70,6 @@ test_script:
     rmdir /s /q ansi-c\arch_flags_mthumb_good
     rmdir /s /q ansi-c\Forward_Declaration2
     rmdir /s /q ansi-c\Incomplete_Type1
-    rmdir /s /q ansi-c\Union_Padding1
     rmdir /s /q ansi-c\Universal_characters1
     rmdir /s /q ansi-c\function_return1
     rmdir /s /q ansi-c\gcc_attributes7

buildspec-windows.yml

@@ -34,7 +34,6 @@ phases:
         Remove-Item ansi-c\arch_flags_mthumb_good -Force -Recurse
         Remove-Item ansi-c\Forward_Declaration2 -Force -Recurse
         Remove-Item ansi-c\Incomplete_Type1 -Force -Recurse
-        Remove-Item ansi-c\Union_Padding1 -Force -Recurse
         Remove-Item ansi-c\Universal_characters1 -Force -Recurse
         Remove-Item ansi-c\function_return1 -Force -Recurse
         Remove-Item ansi-c\gcc_attributes7 -Force -Recurse

src/ansi-c/c_typecheck_type.cpp

@@ -927,7 +927,13 @@ void c_typecheck_baset::typecheck_compound_body(
   if(type.id()==ID_struct)
     add_padding(to_struct_type(type), *this);
   else if(type.id()==ID_union)
+  {
+    // Visual Studio ignores padding on unions
+    if(config.ansi_c.mode == configt::ansi_ct::flavourt::VISUAL_STUDIO)
+      type.remove(ID_C_packed);
+
     add_padding(to_union_type(type), *this);
+  }
 
   // Now remove zero-width bit-fields, these are just
   // for adjusting alignment.