On 6/14/23 09:31, Alex Coplan wrote:
Hi,
This is a v2 patch addressing feedback for:
https://gcc.gnu.org/pipermail/gcc-patches/2023-June/621050.html
macOS SDK headers using the CF_ENUM macro can expand to invalid C++ code
of the form:
typedef enum T : BaseType T;
i.e. an elaborated-type-specifier with an additional enum-base.
Upstream LLVM can be made to accept the above construct with
-Wno-error=elaborated-enum-base.
This patch adds the -Welaborated-enum-base warning to GCC and adjusts
the C++ parser to emit this warning instead of rejecting this code
outright.
The macro expansion in the macOS headers occurs in the case that the
compiler declares support for enums with underlying type using
__has_feature, see
https://gcc.gnu.org/pipermail/gcc-patches/2023-May/618450.html
GCC rejecting this construct outright means that GCC fails to bootstrap
on Darwin in the case that it (correctly) implements __has_feature and
declares support for C++ enums with underlying type.
With this patch, GCC can bootstrap on Darwin in combination with the
(WIP) __has_feature patch posted at:
https://gcc.gnu.org/pipermail/gcc-patches/2023-May/617878.html
Bootstrapped/regtested on aarch64-linux-gnu and x86_64-apple-darwin.
OK for trunk?
Thanks,
Alex
gcc/c-family/ChangeLog:
* c.opt (Welaborated-enum-base): New.
+Welaborated-enum-base
+C++ ObjC++ Var(warn_elaborated_enum_base) Warning Init(1)
+Warn if an additional enum-base is used in an elaborated-type-specifier.
+That is, if an enum with given underlying type and no enumerator list
+is used in a declaration other than just a standalone declaration of the
+enum.
Just the first line of description here; the rest should go in
doc/invoke.texi.
Jason
