Building a x86_64-pc-cygwin cross compiler for x86_64-pc-linux-gnu

[Brian Inglis]

On 2024-12-13 08:13, Johannes Khoshnazar-Thoma via Cygwin wrote:
> Hi list,
> 
> At the moment I am stuck building a cygwin gcc compiler that runs on
> Linux and creates cygwin executables.
> 
> Here's what I did:
> 
> Downloaded and installed binutils:
> 
> git clone --depth 1 -b master https://sourceware.org/git/binutils-gdb.git binutils
> cd binutils
> ./configure --prefix=/home/johannes/cygwin-build-gcc/sysroot/ --disable-shared 
> --enable-static --with-sysroot=/home/johannes/cygwin-build-gcc/sysroot/ -- 
> target=x86_64-pc-cygwin --disable-multilib --disable-nls --enable-lto --disable-gdb
> make -j 10
> make install
> 
> which went fine.
> 
> Now after trying to compile gcc it (later) complains about missing windows.h 
> header.
> So I downloaded and installed the MinGW-w64 package, configured and installed it
> (also to this sysroot but in the x86_64-pc-cygwin directory:
> 
> git clone --depth 1 -b master https://git.code.sf.net/p/mingw-w64/mingw-w64 
> mingw-w64
> cd mingw-w64
> ./configure --build=x86_64-pc-linux-gnu --host=x86_64-w64-mingw32 \
> --prefix=/home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin --without-crt
> make install
> 
> (I also tried with --host=x86_64-pc-cygwin)
> 
> Question: As far as I understood it, installing the MinGW headers is a prerequisite
> to building a x86_64-pc-cygwin cross compiler (because libgcc will need certain
> windows headers). Is that correct?
> 
> Then I tried various gcc configure options:
> 
> git clone --depth 1 -b releases/gcc-14 https://gcc.gnu.org/git/gcc.git gcc
> cd gcc
> ./contrib/download_prerequisites
> ../configure --target=x86_64-pc-cygwin --host=x86_64-pc-linux --disable-shared \
> --enable-static --disable-multilib --prefix=/home/johannes/cygwin-build-gcc/ 
> sysroot/ \
> --enable-languages=c,c++ --disable-nls --enable-threads=posix \
> --with-newlib=/home/johannes/cygwin-build-gcc/newlib-cygwin \
> --with-cygwin=/home/johannes/cygwin-build-gcc/newlib-cygwin --with-system-libunwind
> make -j 8
> 
> Building gcc (xgcc) works fine but when the stage1 compiler tries to compile
> libgcc I get lots of errors complaining about certain types not found:
> 
> Compiler command line is:
> 
> /home/johannes/cygwin-build-gcc/gcc/build/./gcc/xgcc \
> -B/home/johannes/cygwin-build-gcc/gcc/build/./gcc/ \
> -B/home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/bin/ \
> -B/home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/lib/ \
> -isystem /home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/include \
> -isystem /home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/sys-include    \
> -g -O2 -O2 -I../../../libgcc/../winsup/w32api/include -I../../../libgcc/../ 
> winsup/include \
> -I../../../libgcc/../winsup/cygwin/include -g -O2 -DIN_GCC - 
> DCROSS_DIRECTORY_STRUCTURE  \
> -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wstrict-prototypes - 
> Wmissing-prototypes \
> -Wold-style-definition  -isystem ./include   -g -DIN_LIBGCC2 -fbuilding-libgcc \
> -fno-stack-protector -Dinhibit_libc  -I. -I. -I../.././gcc -I../../../libgcc \
> -I../../../libgcc/. -I../../../libgcc/../gcc -I../../../libgcc/../include \
> -I../../../libgcc/config/libbid -DENABLE_DECIMAL_BID_FORMAT -DHAVE_CC_TLS - 
> DUSE_EMUTLS  \
> -o unwind-seh.o -MT unwind-seh.o -MD -MP -MF unwind-seh.dep -fexceptions -c \
> ../../../libgcc/unwind-seh.c
> 
> First few error outputs are:
> 
> In file included from /home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/ 
> include/winnt.h:16,
>                   from /home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/ 
> include/minwindef.h:163,
>                   from /home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/ 
> include/windef.h:9,
>                   from /home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/ 
> include/windows.h:69,
>                   from ./unwind.h:34,
>                   from ../../../libgcc/unwind-seh.c:29:
> /home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/include/ 
> ctype.h:43:17:error: unknown type name 'wctype_t'
>     43 |   _CRTIMP const wctype_t * __cdecl __pwctype_func(void);
>        |                 ^~~~~~~~
> /home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/include/ctype.h:123:24 
> error: unknown type name 'wint_t'
>    123 |   int __cdecl iswalpha(wint_t _C);
>        |                        ^~~~~~
> /home/johannes/cygwin-build-gcc/sysroot/x86_64-pc-cygwin/include/ctype.h:124:24 
> error: unknown type name 'wint_t'
>    124 |   int __cdecl iswupper(wint_t _C);
>        |                        ^~~~~~
> 
> followed by many others.
> 
> Researching a bit showed that there is a _cygwin.h header that #defines 
> _INTPTR_T_DEFINED
> to prevent corecrt.h to typedef intptr_t. But in my case the cygwin headers are not
> included.
> 
> I also tried to symlink winsup to the gcc root directory: same result plus
> a non-existent header:
> 
> ../../../libgcc/../winsup/cygwin/include/features.h:13:10: fatal error: sys/ 
> features.h: No such file or directory
>     13 | #include <sys/features.h>
> 
> Is there a web resource that explains how to create a cygwin cross compiler
> for Linux? Or even better a shell script that does it? What should I do to
> fix the intptr_t issue?

Read the instructions:

	https://x.cygwin.com/docs/cg/cross.html

Recipe for Fedora:

	https://cygwin.com/pipermail/cygwin-cvs/2020q3/014567.html

Fedora copr:

	https://copr.fedorainfracloud.org/coprs/yselkowitz/cygwin/

Posts:

	https://inbox.sourceware.org/cygwin/?q=s:cross

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer     but when there is no more to cut
                                 -- Antoine de Saint-Exupéry