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Recent libslirp commit broke Qemu network stack: qemu and libslirp teams should settle on SOCKET handler type
Description of problem:
https://gitlab.freedesktop.org/slirp/libslirp/-/commit/72f85005a2307fd0961543e3cea861ad7a4d201e introduced regression causing QEMU compilation for Windows to error out due to missing 64-bit SOCKET handler pointer type.
```
x86_64-w64-mingw32-gcc -m64 ... -MD -MQ libcommon.a.p/net_slirp.c.obj -MF libcommon.a.p/net_slirp.c.obj.d -o libcommon.a.p/net_slirp.c.obj -c ../net/slirp.c
../net/slirp.c:289:25: error: initialization of 'void (*)(slirp_os_socket, void *)' {aka 'void (*)(long long unsigned int, void *)'} from incompatible pointer type 'void (*)(int, void *)' [-Wincompatible-pointer-types]
289 | .register_poll_fd = net_slirp_register_poll_fd,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~
../net/slirp.c:289:25: note: (near initialization for 'slirp_cb.register_poll_fd')
../net/slirp.c:290:27: error: initialization of 'void (*)(slirp_os_socket, void *)' {aka 'void (*)(long long unsigned int, void *)'} from incompatible pointer type 'void (*)(int, void *)' [-Wincompatible-pointer-types]
290 | .unregister_poll_fd = net_slirp_unregister_poll_fd,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
../net/slirp.c:290:27: note: (near initialization for 'slirp_cb.unregister_poll_fd')
../net/slirp.c: In function 'net_slirp_poll_notify':
../net/slirp.c:367:28: error: passing argument 3 of 'slirp_pollfds_fill' from incompatible pointer type [-Wincompatible-pointer-types]
367 | net_slirp_add_poll, poll->pollfds);
| ^~~~~~~~~~~~~~~~~~
| |
| int (*)(int, int, void *)
In file included from ../net/slirp.c:41:
/home/cross-qemu-deps/include/slirp/libslirp.h:255:40: note: expected 'SlirpAddPollCb' {aka 'int (*)(long long unsigned int, int, void *)'} but argument is of type 'int (*)(int, int, void *)'
255 | SlirpAddPollCb add_poll, void *opaque);
| ~~~~~~~~~~~~~~~^~~~~~~~
```
Possible solution relying on cross-platform MACRO: https://handsonnetworkprogramming.com/articles/socket-function-return-value-windows-linux-macos/
Steps to reproduce:
1. Prepare cross-compilation build of qemu 9.1.0 using following steps (It's not necessary to set up a virtual machine if your main OS has good mingw repository, like Fedora, Arch linux, Manjaro. But if you're on Debian or Ubuntu, it's required):
2. Download official Fedora workstation 40 x86_64 ISO and install it to a virtual disk and boot that disk.
3. On Fedora, do:\
`wget https://download.qemu.org/qemu-9.1.0.tar.xz`\
` tar xvJf qemu-9.1.0.tar.xz`\
` cd qemu-9.1.0`
4. `sudo yum install git meson ninja-build python3-sphinx python3-sphinx_rtd_theme gcc mingw64-gcc mingw64-pkg-config mingw64-glib2`
5. `git clone https://gitlab.freedesktop.org/slirp/libslirp.git`
6. create file x86_64-w64-mingw32.txt in qemu-9.1.0 directory with the content as follows:
```
[binaries]
c = '/usr/bin/x86_64-w64-mingw32-gcc'
cpp = '/usr/bin/x86_64-w64-mingw32-g++'
ar = '/usr/bin/x86_64-w64-mingw32-ar'
strip = '/usr/bin/x86_64-w64-mingw32-strip'
pkg-config = '/usr/bin/x86_64-w64-mingw32-pkg-config'
exe_wrapper = 'wine'
[host_machine]
system = 'windows'
cpu_family = 'x86_64'
cpu = 'i686'
endian = 'little'
```
7. Run 2 commands:
`export CROSS_QEMU_DEPS="/home/cross-qemu-deps"`\
` sudo mkdir -p $CROSS_QEMU_DEPS`
8. Install libslirp so that future qemu binaries can have internet access via \`-netdev user\`\
\
`cd libslirp`\
\
` meson setup --cross-file ../x86_64-w64-mingw32.txt --prefix "$CROSS_QEMU_DEPS" build-mingw/`\
` meson compile -C build-mingw`\
` cd build-mingw`\
` ninja install`
9. Set environment variables for cross-compilation\
\
` sudo find / -type f -name '*.pc'` and make sure all mingw \*.pc files live in /usr/x86_64-w64-mingw32/sys-root/mingw/lib/pkgconfig/. Correct this path in PKG_CONFIG_PATH if you see it was altered by mingw or package contributors.\
\
` export PKG_CONFIG_PATH="/usr/x86_64-w64-mingw32/sys-root/mingw/lib/pkgconfig/:$PKG_CONFIG_PATH"`\
` export PKG_CONFIG_LIBDIR="${CROSS_QEMU_DEPS}/lib/pkgconfig/:$PKG_CONFIG_LIBDIR"`\
` export PKG_CONFIG_SYSROOT_DIR=""`
10. Configure Qemu makefile:\
\
`cd ../../`\
`./configure --cross-prefix=x86_64-w64-mingw32- --enable-slirp`\
\
and make sure you see this in the output of configure:\
`Compilation`\
`host CPU : x86_64`\
`host endianness : little`\
`C compiler : x86_64-w64-mingw32-gcc -m64`\
`Host C compiler : cc`
11. Cross-compile qemu: `` make -j`nproc` ``
12. Get the error `initialization of 'void (*)(slirp_os_socket, void *)' {aka 'void (*)(long long unsigned int, void *)'} from incompatible pointer type 'void (*)(int, void *)'` as above.
Additional information:
After having seen this bug, do these steps (revert to the commit right before the buggy one).
` cd libslirp`\
` git reset --hard 5e97a93b`
` meson setup --cross-file ../x86_64-w64-mingw32.txt --prefix "$CROSS_QEMU_DEPS" build-mingw/ --reconfigure`\
` meson compile -C build-mingw`\
` cd build-mingw`\
` ninja install`
`` cd ../../ ``\
`` ./configure --cross-prefix=x86_64-w64-mingw32- --enable-slirp ``\
`` make -j`nproc` ``
=\> Cross-compilation comes to an end just fine, building all compilation targets without any errors.
|