Re: Packing of union fields and bool_bf

[Paul Eggert <eggert@cs.ucla.edu>]

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On 10/13/2018 10:58 AM, Tom Tromey wrote:
> From https://docs.microsoft.com/en-us/cpp/c-language/padding-and-alignment-of-structure-members?view=vs-2017:
>
>     Adjacent bit fields are packed into the same 1-, 2-, or 4-byte
>     allocation unit if the integral types are the same size


It's silly to require the integral types to be the same size, since the
actual size is given by the number of bits in the bitfield. But if it's
the Microsoft API we can't change it. Does the attached patch work
around the problem?


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diff --git a/src/conf_post.h b/src/conf_post.h
index 683a96f936..dbe5befcf9 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -54,10 +54,10 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
     ((v) < __GNUC__ + ((w) < __GNUC_MINOR__ + ((x) <= __GNUC_PATCHLEVEL__)))
 #endif
 
-/* The type of bool bitfields.  Needed to compile Objective-C with
-   standard GCC.  It was also needed to port to pre-C99 compilers,
-   although we don't care about that any more.  */
-#if NS_IMPL_GNUSTEP
+/* The type of bool bitfields.  Preferably bool for better debugging,
+   bu unsigned int on MS-Windows to avoid struct bloat, and unsigned
+   int for Objective-C with standard GCC.  */
+#if defined DOS_NT || NS_IMPL_GNUSTEP
 typedef unsigned int bool_bf;
 #else
 typedef bool bool_bf;