On Sun 24 Oct 2021, Paul Eggert wrote: > On 10/24/21 9:58 AM, Eli Zaretskii wrote: >> We could try all that, but not on the release branch. There, I'd like >> a simple and safe fix. Is such a thing possible? > > Andy suggested a simple fix that I quoted here: > > https://lists.gnu.org/r/emacs-devel/2021-10/msg01698.html > > We could apply that patch just to ntlib.c and just in emacs-28 (do not merge > to master) as Andy says that works for him;
Yes, that minimal fix bootstraps on emacs-28 and master with 64bit mingw64. > and we could then apply the more-systematic patch of > <https://lists.gnu.org/r/emacs-devel/2021-10/msg01697.html> to master. Andy's > patch is definitely safe for GNU and POSIXish hosts. I don't know whether it > suffices for all MS-Windows platforms and Emacs builds. The patch still needs some work: a) The symbol in conf_post.h is DEFER_MS_W32_H (not DEFER_MS_W3_H), so needs fixing in the patch. b) BASE_CFLAGS in nt/Makefile.in needs changes to match the include switches in lib-src/Makefile.in (so that config.h, conf_post.h and attribute.h etc can be found). After fixing those minor issues, emacs-28 bootstraps with only one additional warning due to the patch: C:/emacs/git/emacs/emacs-28/lib-src/ntlib.c:294: warning: "IS_DIRECTORY_SEP" redefined 294 | #define IS_DIRECTORY_SEP(x) ((x) == '/' || (x) == '\\') | In file included from C:/emacs/git/emacs/emacs-28/lib-src/ntlib.c:24: ../src/config.h:1563: note: this is the location of the previous definition 1563 | #define IS_DIRECTORY_SEP(_c_) ((_c_) == '/' || (_c_) == '\\') | (There are a few other new warnings in the build with either approach, probably due to additional checks that have appeared after upgrading from gcc 10.3 to gcc 11.2.) I understand Eli's desire to avoid using this patch on emacs-28 as the changes are potentially destabilising this late in the release cycle. >> Can you explain why config.h is needed there, and why only for GCC 11? > config.h is needed because it defines macros used by lib/string.h and other > lib/*.h files that come from Gnulib. I don't know why the problem occurs only > for GCC 11 on MS-Windows platforms, as I would think it'd also occur with > earlier GCC versions. Older GCC versions don't do the static checking I > mentioned, so the macros do not help checking with older GCC. The macros can > safely be #defined to empty as Andy's patch suggested, so long as config.h > isn't included (as it would define them differently). The downsides of Andy's > approach (as compared to the more-systematic patch) is that you lose out some > static checking with recent GCC, and I worry (without really knowing) that > similar problems may lurk in other MS-Windows-specific .c files on some other > MS-Windows platforms. My suggestion to define the macros was a minimal workaround to get emacs building again for me until proper fix could be developed. I suspect the issue has been in the gnulib header for some time, but has only been triggered in the build after upgrading to gcc >=11 as otherwise the relevant code is not built (it is guarded with a gcc version check). AndyM
