https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66655
--- Comment #17 from Roger Orr <rogero at howzatt dot demon.co.uk> --- As you say, there seems to be another, unrelated, problem with the current trunk and cygwin. However, I have now successfully built gcc version 232300 under cygwin with this patch. Unfortunately, if I try to compile and execute the test program: $ g++ -O2 -fno-inline pr66655.C pr66655_1.cc $ ./a.exe it produces a segmentation fault, just as reported with the mingw build. So it does seem that cygwin needs the problem fixed, just like mingw, but that the orginal fix has other, unfortunate, consequences.
