Hello,
after this patch on the emacs-26 branch I can't build it no more:
CCLD temacs
/bin/mkdir -p ../etc
make -C ../lisp update-subdirs
make[2]: Entering directory '/home/drot/build/emacs/lisp'
make[2]: Leaving directory '/home/drot/build/emacs/lisp'
./temacs --batch --load loadup bootstrap
Loading loadup.el (source)...
Using load-path (/home/drot/build/emacs/lisp /home/drot/build/emacs/lisp/emacs-lisp /home/drot/build/emacs/lisp/progmodes /home/drot/build/emacs/lisp/language
/home/drot/build/emacs/lisp/international /home/drot/build/emacs/lisp/textmodes /home/drot/build/emacs/lisp/vc)
Loading emacs-lisp/byte-run (source)...
Loading emacs-lisp/backquote (source)...
Loading subr (source)...
Fatal error 6: Aborted
Backtrace:
./temacs[0x81624a5]
./temacs[0x81431ea]
./temacs[0x816255f]
./temacs[0x81acea1]
./temacs[0x81acb91]
./temacs[0x81ad4f9]
./temacs[0x81cd0c9]
./temacs[0x81cd98e]
./temacs[0x81cf682]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81ce1ff]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81cde01]
./temacs[0x81cdfa6]
./temacs[0x81cd2bc]
./temacs[0x81ce38e]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81cea3a]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81cf682]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81ce1ff]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81cde01]
./temacs[0x81cdfa6]
./temacs[0x81cd2bc]
./temacs[0x81ce38e]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81cea3a]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81cf682]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81ce1ff]
./temacs[0x81cd673]
./temacs[0x81cd98e]
./temacs[0x81cde01]
./temacs[0x81cdfa6]
./temacs[0x81cd2bc]
./temacs[0x81cd461]
./temacs[0x81cd98e]
./temacs[0x81cde01]
./temacs[0x81ca9f6]
./temacs[0x81cce33]
./temacs[0x81ccfa3]
./temacs[0x81cd359]
./temacs[0x81cd98e]
./temacs[0x81cde01]
...
Makefile:737: recipe for target 'bootstrap-emacs' failed
make[1]: *** [bootstrap-emacs] Aborted
make[1]: Leaving directory '/home/drot/build/emacs/src'
Makefile:416: recipe for target 'src' failed
make: *** [src] Error 2
This is with the following GCC version: