How to cross compile from linux to windows

[autoantwort]

I try to build libbacktrace for mingw from linux, I am using the mxe environment. I have created the triplet file:

# from https://stackoverflow.com/questions/58777810/how-to-integrate-vcpkg-in-linux-with-cross-build-toolchain-as-well-as-sysroot

set(VCPKG_TARGET_ARCHITECTURE x64)
set(VCPKG_CRT_LINKAGE dynamic)
set(VCPKG_LIBRARY_LINKAGE static)

set(VCPKG_CMAKE_SYSTEM_NAME MinGW)

set(VCPKG_CHAINLOAD_TOOLCHAIN_FILE /usr/src/mxe/usr/x86_64-w64-mingw32.shared.posix/share/cmake/mxe-conf.cmake)

with

mxe-conf.cmake

[root:/usr/src/mxe] # cat usr/x86_64-w64-mingw32.shared.posix/share/cmake/mxe-conf.cmake
# This file is part of MXE. See LICENSE.md for licensing information.

# https://cmake.org/cmake/help/latest

# Can't set `cmake_minimum_required` or `cmake_policy` in toolchain
# since toolchain is read before CMakeLists.txt
# See `target-cmake.in` for CMAKE_POLICY_DEFAULT_CMPNNNN

# Check if we are using mxe supplied version
#   - toolchain is included multiple times so set a guard in
#     environment to suppress duplicate messages
if(NOT ${CMAKE_COMMAND} STREQUAL /usr/src/mxe/usr/x86_64-pc-linux-gnu/bin/cmake AND NOT DEFINED ENV{_MXE_CMAKE_TOOLCHAIN_INCLUDED})
    message(WARNING "
** Warning: direct use of toolchain file is deprecated
** Please use prefixed wrapper script instead:
     x86_64-w64-mingw32.shared.posix-cmake [options] 
       - uses mxe supplied cmake version 3.19.2
       - loads toolchain
       - loads common run results
       - sets various policy defaults
    ")
    set(ENV{_MXE_CMAKE_TOOLCHAIN_INCLUDED} TRUE)
endif()

# Use CACHE variables to allow user setting with `-D`
# Use CACHE FORCE in rare cases of misconfigured CMakeLists.txt
#   - e.g include(FindPkgConfig)
#     https://github.com/mxe/mxe/issues/1023
#   - projects may still set these in which case FORCE doesn't have
#     any advantage, just causes inconvenience
#     https://github.com/mxe/mxe/pull/1621#discussion_r106937505
# Use normal variables expected to be set by toolchain/system
#   - projects should test for these values and not try to override

## General configuration
set(CMAKE_SYSTEM_NAME Windows)
set(CMAKE_SYSTEM_PROCESSOR x86_64 CACHE STRING "System Processor")
set(MSYS 1)
set(CMAKE_EXPORT_NO_PACKAGE_REGISTRY ON)
# Workaround for https://www.cmake.org/Bug/view.php?id=14075
set(CMAKE_CROSS_COMPILING ON)


## Library config
set(BUILD_SHARED_LIBS ON CACHE BOOL "BUILD_SHARED_LIBS")
set(BUILD_STATIC_LIBS OFF CACHE BOOL "BUILD_STATIC_LIBS")
set(BUILD_SHARED ON CACHE BOOL "BUILD_SHARED")
set(BUILD_STATIC OFF CACHE BOOL "BUILD_STATIC")
set(LIBTYPE SHARED)


## Paths etc.
# These MODEs shouldn't be changed by users, we only want headers/libs
# from cross-build and "never" want binaries. We do, however, want
# `*-config` scripts but there's no way to instruct cmake to do that.
#
# The best solution may be to whitelist utilities
#   https://github.com/mxe/mxe/issues/1667
# and symlink them to an additional root path, changing PROGRAM to ONLY

set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)

# Allow user to specify list of locations to search
set(CMAKE_FIND_ROOT_PATH /usr/src/mxe/usr/x86_64-w64-mingw32.shared.posix CACHE PATH "List of root paths to search on the filesystem")
set(CMAKE_PREFIX_PATH /usr/src/mxe/usr/x86_64-w64-mingw32.shared.posix CACHE PATH "List of directories specifying installation prefixes to be searched")
set(CMAKE_INSTALL_PREFIX /usr/src/mxe/usr/x86_64-w64-mingw32.shared.posix CACHE PATH "Installation Prefix")
# For custom mxe FindPackage scripts
set(CMAKE_MODULE_PATH "/usr/src/mxe/usr/share/cmake/modules" ${CMAKE_MODULE_PATH})

# projects (mis)use `-isystem` to silence warnings from 3rd-party
# source (among other things). gcc6 introduces changes to search
# order which breaks this usage.
#   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70129
#   https://gitlab.kitware.com/cmake/cmake/issues/16291
#   https://gitlab.kitware.com/cmake/cmake/issues/16919
set(CMAKE_C_IMPLICIT_INCLUDE_DIRECTORIES /usr/src/mxe/usr/x86_64-w64-mingw32.shared.posix/include)
set(CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES /usr/src/mxe/usr/x86_64-w64-mingw32.shared.posix/include)


## Programs
set(CMAKE_C_COMPILER /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-gcc)
set(CMAKE_CXX_COMPILER /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-g++)
set(CMAKE_Fortran_COMPILER /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-gfortran)
set(CMAKE_RC_COMPILER /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-windres)
# CMAKE_RC_COMPILE_OBJECT is defined in:
#     /share/cmake-X.Y/Modules/Platform/Windows-windres.cmake
set(CPACK_NSIS_EXECUTABLE x86_64-w64-mingw32.shared.posix-makensis)

## Individual package configuration
file(GLOB mxe_cmake_files
    "/usr/src/mxe/usr/x86_64-w64-mingw32.shared.posix/share/cmake/mxe-conf.d/*.cmake"
)
foreach(mxe_cmake_file ${mxe_cmake_files})
    include(${mxe_cmake_file})
endforeach()
set(CMAKE_CROSSCOMPILING_EMULATOR "/usr/bin/wine")

and set(VCPKG_MAKE_BUILD_TRIPLET --host=mingw32) added to libbacktrace/portfile.cmake:11.
But the output is:
config-x64-linux-windows-static-dbg-out.log:

checking build system type... x86_64-pc-linux-gnu
checking host system type... i686-pc-mingw32
checking target system type... i686-pc-mingw32
checking for mingw32-gcc... /usr/bin/gcc
checking whether the C compiler works... no

config-x64-linux-windows-static-dbg-err.log:

configure: error: in `/builds/leander.schulten/Lichtsteuerung/vcpkg/buildtrees/libbacktrace/x64-linux-windows-static-dbg':
configure: error: C compiler cannot create executables
See `config.log' for more details

with

config.log

This file contains any messages produced by compilers while
running configure, to aid debugging if configure makes a mistake.

It was created by package-unused configure version-unused, which was
generated by GNU Autoconf 2.69.  Invocation command line was

  $ ./../src/876b545088-bf2d416700.clean/configure --host=mingw32 --disable-silent-rules --verbose --disable-shared --enable-static --prefix=/builds/leander.schulten/Lichtsteuerung/vcpkg_installed/x64-linux-windows-static/debug --bindir=${prefix}/../tools/libbacktrace/debug/bin --sbindir=${prefix}/../tools/libbacktrace/debug/sbin --includedir=${prefix}/../include --datarootdir=${prefix}/share/libbacktrace

## --------- ##
## Platform. ##
## --------- ##

hostname = runner-cdb9c124-project-10017-concurrent-0
uname -m = x86_64
uname -r = 4.4.0-203-generic
uname -s = Linux
uname -v = #235-Ubuntu SMP Tue Feb 2 02:49:08 UTC 2021

/usr/bin/uname -p = unknown
/bin/uname -X     = unknown

/bin/arch              = unknown
/usr/bin/arch -k       = unknown
/usr/convex/getsysinfo = unknown
/usr/bin/hostinfo      = unknown
/bin/machine           = unknown
/usr/bin/oslevel       = unknown
/bin/universe          = unknown

PATH: /usr/local/sbin
PATH: /usr/local/bin
PATH: /usr/sbin
PATH: /usr/bin
PATH: /sbin
PATH: /bin
PATH: /usr/src/mxe/usr/bin
PATH: /builds/leander.schulten/Lichtsteuerung/vcpkg/downloads/tools/ninja-1.10.1-linux


## ----------- ##
## Core tests. ##
## ----------- ##

configure:2379: checking build system type
configure:2393: result: x86_64-pc-linux-gnu
configure:2413: checking host system type
configure:2426: result: i686-pc-mingw32
configure:2446: checking target system type
configure:2459: result: i686-pc-mingw32
configure:2499: checking for mingw32-gcc
configure:2526: result: /usr/bin/gcc
configure:2795: checking for C compiler version
configure:2804: /usr/bin/gcc --version >&5
gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

configure:2815: $? = 0
configure:2804: /usr/bin/gcc -v >&5
Using built-in specs.
COLLECT_GCC=/usr/bin/gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/6/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 6.3.0-18+deb9u1' --with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-6 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --with-target-system-zlib --enable-objc-gc=auto --enable-multiarch --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1) 
configure:2815: $? = 0
configure:2804: /usr/bin/gcc -V >&5
gcc: error: unrecognized command line option '-V'
gcc: fatal error: no input files
compilation terminated.
configure:2815: $? = 1
configure:2804: /usr/bin/gcc -qversion >&5
gcc: error: unrecognized command line option '-qversion'; did you mean '--version'?
gcc: fatal error: no input files
compilation terminated.
configure:2815: $? = 1
configure:2835: checking whether the C compiler works
configure:2857: /usr/bin/gcc -g  -L/builds/leander.schulten/Lichtsteuerung/vcpkg_installed/x64-linux-windows-static/debug/lib  conftest.c -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 >&5
/usr/bin/ld: cannot find -lkernel32
/usr/bin/ld: cannot find -luser32
/usr/bin/ld: cannot find -lgdi32
/usr/bin/ld: cannot find -lwinspool
/usr/bin/ld: cannot find -lshell32
/usr/bin/ld: cannot find -lole32
/usr/bin/ld: cannot find -loleaut32
/usr/bin/ld: cannot find -luuid
/usr/bin/ld: cannot find -lcomdlg32
/usr/bin/ld: cannot find -ladvapi32
collect2: error: ld returned 1 exit status
configure:2861: $? = 1
configure:2899: result: no
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME "package-unused"
| #define PACKAGE_TARNAME "libbacktrace"
| #define PACKAGE_VERSION "version-unused"
| #define PACKAGE_STRING "package-unused version-unused"
| #define PACKAGE_BUGREPORT ""
| #define PACKAGE_URL ""
| /* end confdefs.h.  */
| 
| int
| main ()
| {
| 
|   ;
|   return 0;
| }
configure:2904: error: in `/builds/leander.schulten/Lichtsteuerung/vcpkg/buildtrees/libbacktrace/x64-linux-windows-static-dbg':
configure:2906: error: C compiler cannot create executables
See `config.log' for more details

## ---------------- ##
## Cache variables. ##
## ---------------- ##

ac_cv_build=x86_64-pc-linux-gnu
ac_cv_env_CC_set=set
ac_cv_env_CC_value=/usr/bin/gcc
ac_cv_env_CFLAGS_set=set
ac_cv_env_CFLAGS_value=-g
ac_cv_env_CPPFLAGS_set=
ac_cv_env_CPPFLAGS_value=
ac_cv_env_CPP_set=set
ac_cv_env_CPP_value=/usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-cpp
ac_cv_env_DSYMUTIL_set=
ac_cv_env_DSYMUTIL_value=
ac_cv_env_LDFLAGS_set=set
ac_cv_env_LDFLAGS_value='-L/builds/leander.schulten/Lichtsteuerung/vcpkg_installed/x64-linux-windows-static/debug/lib '
ac_cv_env_LIBS_set=set
ac_cv_env_LIBS_value='-lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32'
ac_cv_env_NM_set=
ac_cv_env_NM_value=
ac_cv_env_OBJCOPY_set=
ac_cv_env_OBJCOPY_value=
ac_cv_env_build_alias_set=
ac_cv_env_build_alias_value=
ac_cv_env_host_alias_set=set
ac_cv_env_host_alias_value=mingw32
ac_cv_env_target_alias_set=
ac_cv_env_target_alias_value=
ac_cv_host=i686-pc-mingw32
ac_cv_prog_CC=/usr/bin/gcc
ac_cv_target=i686-pc-mingw32

## ----------------- ##
## Output variables. ##
## ----------------- ##

ACLOCAL=''
ALLOC_FILE=''
AMTAR=''
AM_BACKSLASH=''
AM_DEFAULT_V=''
AM_DEFAULT_VERBOSITY=''
AM_V=''
AR='/usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-ar'
AUTOCONF=''
AUTOHEADER=''
AUTOMAKE=''
AWK=''
BACKTRACE_FILE=''
BACKTRACE_SUPPORTED=''
BACKTRACE_SUPPORTS_DATA=''
BACKTRACE_SUPPORTS_THREADS=''
BACKTRACE_USES_MALLOC=''
CC='/usr/bin/gcc'
CFLAGS='-g'
CLOCK_GETTIME_LINK=''
COMM=''
CPP='/usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-cpp'
CPPFLAGS=''
CYGPATH_W=''
DEFS=''
DSYMUTIL=''
DUMPBIN=''
DWZ=''
ECHO_C=''
ECHO_N='-n'
ECHO_T=''
EGREP=''
EXEEXT=''
EXTRA_FLAGS=''
FGREP=''
FORMAT_FILE=''
GREP=''
HAVE_COMM_FALSE=''
HAVE_COMM_TRUE=''
HAVE_COMPRESSED_DEBUG_FALSE=''
HAVE_COMPRESSED_DEBUG_TRUE=''
HAVE_DWARF5_FALSE=''
HAVE_DWARF5_TRUE=''
HAVE_DWZ_FALSE=''
HAVE_DWZ_TRUE=''
HAVE_ELF_FALSE=''
HAVE_ELF_TRUE=''
HAVE_LIBLZMA_FALSE=''
HAVE_LIBLZMA_TRUE=''
HAVE_MINIDEBUG_FALSE=''
HAVE_MINIDEBUG_TRUE=''
HAVE_OBJCOPY_DEBUGLINK_FALSE=''
HAVE_OBJCOPY_DEBUGLINK_TRUE=''
HAVE_PTHREAD_FALSE=''
HAVE_PTHREAD_TRUE=''
HAVE_XZ_FALSE=''
HAVE_XZ_TRUE=''
HAVE_ZLIB_FALSE=''
HAVE_ZLIB_TRUE=''
INSTALL_DATA=''
INSTALL_PROGRAM=''
INSTALL_SCRIPT=''
INSTALL_STRIP_PROGRAM=''
LD='/usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-ld'
LDFLAGS='-L/builds/leander.schulten/Lichtsteuerung/vcpkg_installed/x64-linux-windows-static/debug/lib '
LIBOBJS=''
LIBS='-lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32'
LIBTOOL=''
LIPO=''
LN_S=''
LTLIBOBJS=''
MAINT=''
MAINTAINER_MODE_FALSE=''
MAINTAINER_MODE_TRUE=''
MAKEINFO=''
MKDIR_P=''
NATIVE_FALSE=''
NATIVE_TRUE=''
NM=''
NMEDIT=''
OBJCOPY=''
OBJDUMP=''
OBJEXT=''
OTOOL64=''
OTOOL=''
PACKAGE=''
PACKAGE_BUGREPORT=''
PACKAGE_NAME='package-unused'
PACKAGE_STRING='package-unused version-unused'
PACKAGE_TARNAME='libbacktrace'
PACKAGE_URL=''
PACKAGE_VERSION='version-unused'
PATH_SEPARATOR=':'
PIC_FLAG=''
PTHREAD_CFLAGS=''
RANLIB=''
READELF=''
SED=''
SET_MAKE=''
SHELL='/bin/sh'
STRIP=''
USE_DSYMUTIL_FALSE=''
USE_DSYMUTIL_TRUE=''
VERSION=''
VIEW_FILE=''
WARN_FLAGS=''
XZ=''
ac_ct_CC=''
ac_ct_DUMPBIN=''
am__EXEEXT_FALSE=''
am__EXEEXT_TRUE=''
am__isrc=''
am__leading_dot=''
am__tar=''
am__untar=''
bindir='${prefix}/../tools/libbacktrace/debug/bin'
build='x86_64-pc-linux-gnu'
build_alias=''
build_cpu='x86_64'
build_os='linux-gnu'
build_vendor='pc'
datadir='${datarootdir}'
datarootdir='${prefix}/share/libbacktrace'
docdir='${datarootdir}/doc/${PACKAGE_TARNAME}'
dvidir='${docdir}'
exec_prefix='NONE'
host='i686-pc-mingw32'
host_alias='mingw32'
host_cpu='i686'
host_os='mingw32'
host_vendor='pc'
htmldir='${docdir}'
includedir='${prefix}/../include'
infodir='${datarootdir}/info'
install_sh=''
libdir='${exec_prefix}/lib'
libexecdir='${exec_prefix}/libexec'
libtool_VERSION=''
localedir='${datarootdir}/locale'
localstatedir='${prefix}/var'
mandir='${datarootdir}/man'
mkdir_p=''
multi_basedir=''
oldincludedir='/usr/include'
pdfdir='${docdir}'
prefix='/builds/leander.schulten/Lichtsteuerung/vcpkg_installed/x64-linux-windows-static/debug'
program_transform_name='s,x,x,'
psdir='${docdir}'
sbindir='${prefix}/../tools/libbacktrace/debug/sbin'
sharedstatedir='${prefix}/com'
sysconfdir='${prefix}/etc'
target='i686-pc-mingw32'
target_alias='mingw32'
target_cpu='i686'
target_os='mingw32'
target_vendor='pc'

## ----------- ##
## confdefs.h. ##
## ----------- ##

/* confdefs.h */
#define PACKAGE_NAME "package-unused"
#define PACKAGE_TARNAME "libbacktrace"
#define PACKAGE_VERSION "version-unused"
#define PACKAGE_STRING "package-unused version-unused"
#define PACKAGE_BUGREPORT ""
#define PACKAGE_URL ""

configure: exit 77

and $PATH = /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/src/mxe/usr/bin

The only thing that worked is adding

set(VCPKG_MAKE_BUILD_TRIPLET --host=mingw32)
set(ENV{CC} /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-gcc)
set(ENV{CXX} /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-g++)

to ports/libbacktrace/portfile.cmake but this can not be the right solution.

And when I add

message(STATUS "CMAKE_C_COMPILER: ${CMAKE_C_COMPILER}")
message(STATUS "CMAKE_CXX_COMPILER: ${CMAKE_CXX_COMPILER}")

to ports/libbacktrace/portfile.cmake the output shows that the variables are empty. But shouldn't there be any values when I set VCPKG_CHAINLOAD_TOOLCHAIN_FILE?

[Neumann-A]

the toolchain settings are not available in the portfile.cmake. vcpkg_configure_make should access them via vcpkg_get_cmake_vars. there is also a log for the exported variables

[Neumann-A]

according to the config.log

/usr/bin/ld: cannot find -lkernel32
/usr/bin/ld: cannot find -luser32
/usr/bin/ld: cannot find -lgdi32
/usr/bin/ld: cannot find -lwinspool
/usr/bin/ld: cannot find -lshell32
/usr/bin/ld: cannot find -lole32
/usr/bin/ld: cannot find -loleaut32
/usr/bin/ld: cannot find -luuid
/usr/bin/ld: cannot find -lcomdlg32
/usr/bin/ld: cannot find -ladvapi32

You are probably missing an -L flag

[autoantwort]

Ok that is not the only error in config.log

gcc: error: unrecognized command line option '-V'
gcc: fatal error: no input files
compilation terminated.
configure:2815: $? = 1
configure:2804: /usr/bin/gcc -qversion >&5
gcc: error: unrecognized command line option '-qversion'; did you mean '--version'?
gcc: fatal error: no input files

[autoantwort]

But I think the error happens before that: config-x64-linux-windows-static-dbg-out.log:

checking for mingw32-gcc... /usr/bin/gcc
checking whether the C compiler works... no

So it selects the wrong compiler and then tests it, of cause the default linux gcc compiler does not know -lkernel32, ... .
And therefore

set(ENV{CC} /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-gcc)
set(ENV{CXX} /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-g++) 

helped because then the right compiler is selected.

Maybe we need something like

set(ENV{CC} "${VCPKG_DETECTED_CMAKE_C_COMPILER}")
set(ENV{CXX} "${VCPKG_DETECTED_CMAKE_CXX_COMPILER}")

in vcpkg_configure_make.cmake

[autoantwort]

Ok, here: https://github.com/microsoft/vcpkg/blob/master/scripts/cmake/vcpkg_configure_make.cmake#L341
and in the following lines something like that is already done, but only if CMAKE_HOST_WIN32, that must be VCPKG_TARGET_IS_WINDOWS? But then you have to add ifs around the msys things because I don't think they are needed on linux

[autoantwort]

Would be fixed by #17073

[dg0yt]

I try to build libbacktrace for mingw from linux, I am using the mxe environment

Does the title need an edit?

How to cross compile from windows to linux

[autoantwort]

Why?

[dg0yt]

It looks to me like compiling from linux to windows.

[autoantwort]

Yes thats right

[autoantwort]

Oh lol, now I realized that the title is windows to linux :D Yes that is wrong

[dg0yt]

set(ENV{CC} /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-gcc)
set(ENV{CXX} /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-g++)

Does vcpkg detect these compilers at all? AFAIU, it looks for a very restricted set of names:

vcpkg/scripts/toolchains/mingw.cmake

Lines 24 to 25 in a267ab1

	find_program(CMAKE_C_COMPILER "${CMAKE_SYSTEM_PROCESSOR}-w64-mingw32-gcc")
	find_program(CMAKE_CXX_COMPILER "${CMAKE_SYSTEM_PROCESSOR}-w64-mingw32-g++")

So does it work when you symlink /usr/src/mxe/usr/bin/x86_64-w64-mingw32-g++ to /usr/src/mxe/usr/bin/x86_64-w64-mingw32.shared.posix-g++ (same for gcc, windres)?
I mentioned MXE in the mingw docs PR, so it would be good to know that it actually works, or what is needed to make it work.

[autoantwort]

Does vcpkg detect these compilers at all?

I use a toolchain file to set the compilers.

I mentioned MXE in the mingw docs PR, so it would be good to know that it actually works, or what is needed to make it work.

It should work after #17073 gets merged. But there are Problems like #17163

[JackBoosY]

Since #17073 was merged, I think this duscission can be closed.

[autoantwort]

Yes, and there is now documentation how to use vcpkg with mingw