Hi there,

I've been having trouble compiling the unit tests for wxWidgets3.1-3.1.5 
on Cygwin. The same tests build just fine on my Linux Mint 20.3 install, 
however that is using GCC 9.3.0 instead of Cygwin's 11.2.0.

Attached is the full build log, but I will also point out my ideas about 
particular issues here.

Note: -Werror=format-security is used in the Makefile. I couldn't find 
exactly what this does, but I'm probably looking in the wrong place - 
the manpage. Perhaps the following could also be explained by 
differences from GCC 9 to 11?

The first is:

In file included from /usr/include/unistd.h:4,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/filefn.h:23,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/utils.h:20,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/cursor.h:75,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/event.h:22,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/evtloop.h:14,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/tests/testprec.h:5,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/tests/allheaders.cpp:433:
/usr/include/sys/unistd.h:23:9: error: redundant redeclaration of ‘int 
chmod(const char*, mode_t)’ in same scope [-Werror=redundant-decls]
    23 | int     chmod (const char *__path, mode_t __mode);
       |         ^~~~~
In file included from /usr/include/sys/_default_fcntl.h:211,
                  from /usr/include/sys/fcntl.h:3,
                  from /usr/include/fcntl.h:12,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/tests/allheaders.cpp:83:
/usr/include/sys/stat.h:137:9: note: previous declaration of ‘int 
chmod(const char*, mode_t)’
   137 | int     chmod (const char *__path, mode_t __mode );
       |         ^~~~~

This doesn't happen on my Linux Mint 20.3 (Ubuntu 20.04) host, so I'm 
assuming this is something to do with the standard library?

Next is:

In file included from /usr/include/unistd.h:4,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/filefn.h:23,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/utils.h:20,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/cursor.h:75,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/event.h:22,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/include/wx/evtloop.h:14,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/tests/testprec.h:5,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/tests/allheaders.cpp:433:
/usr/include/sys/unistd.h:179:9: error: redundant redeclaration of ‘int 
pthread_atfork(void (*)(), void (*)(), void (*)())’ in same scope 
[-Werror=redundant-decls]
   179 | int     pthread_atfork (void (*)(void), void (*)(void), void 
(*)(void));
       |         ^~~~~~~~~~~~~~
In file included from 
/usr/lib/gcc/x86_64-pc-cygwin/11/include/c++/x86_64-pc-cygwin/bits/gthr-default.h:35,
                  from 
/usr/lib/gcc/x86_64-pc-cygwin/11/include/c++/x86_64-pc-cygwin/bits/gthr.h:148,
                  from 
/usr/lib/gcc/x86_64-pc-cygwin/11/include/c++/ext/atomicity.h:35,
                  from 
/usr/lib/gcc/x86_64-pc-cygwin/11/include/c++/bits/ios_base.h:39,
                  from 
/usr/lib/gcc/x86_64-pc-cygwin/11/include/c++/iomanip:40,
                  from 
/home/Hamis/wxwidgets3.1/wxWidgets3.1-3.1.5-1.x86_64/src/wxWidgets-3.1.5/tests/allheaders.cpp:63:
/usr/include/pthread.h:65:5: note: previous declaration of ‘int 
pthread_atfork(void (*)(), void (*)(), void (*)())’
    65 | int pthread_atfork (void (*)(void), void (*)(void), void 
(*)(void));
       |     ^~~~~~~~~~~~~~

Ditto.

Then there are some wxwidgets-specific ones, but I'll make a separate 
thread for those because I have an idea about what might be causing 
them. I'll probably need to ask the wxWidgets people.

Hopefully someone here with more experience can help.

Also of note, is that Cygwin is several times slower at compiling pretty 
much everything for me. Does anyone know if this is GCC 9 vs 11 speed, 
or running Cygwin in Windows 11 in KVM, or something else? I am running 
on AMD Ryzen 3000, if that has anything to do with it.

Hamish