Re: [PATCH] configure: Move preadv check to meson.build

[Paolo Bonzini <pbonzini@redhat.com>]

On 26/01/21 16:58, Peter Maydell wrote:
> Move the preadv availability check to meson.build.  This is what we
> want to be doing for host-OS-feature-checks anyway, but it also fixes
> a problem with building for macOS with the most recent XCode SDK on a
> Catalina host.
> 
> On that configuration, 'preadv()' is provided as a weak symbol, so
> that programs can be built with optional support for it and make a
> runtime availability check to see whether the preadv() they have is a
> working one or one which they must not call because it will
> runtime-assert.  QEMU's configure test passes (unless you're building
> with --enable-werror) because the test program using preadv()
> compiles, but then QEMU crashes at runtime when preadv() is called,
> with errors like:
> 
>    dyld: lazy symbol binding failed: Symbol not found: _preadv
>      Referenced from: /Users/pm215/src/qemu/./build/x86/tests/test-replication
>      Expected in: /usr/lib/libSystem.B.dylib
> 
>    dyld: Symbol not found: _preadv
>      Referenced from: /Users/pm215/src/qemu/./build/x86/tests/test-replication
>      Expected in: /usr/lib/libSystem.B.dylib
> 
> Meson's own function availability check has a special case for macOS
> which adds '-Wl,-no_weak_imports' to the compiler flags, which forces
> the test to require the real function, not the macOS-version-too-old
> stub.
> 
> So this commit fixes the bug where macOS builds on Catalina currently
> require --disable-werror.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   configure   | 16 ----------------
>   meson.build |  4 +++-
>   2 files changed, 3 insertions(+), 17 deletions(-)
> 
> diff --git a/configure b/configure
> index dcc5ea7d630..0e672c3e291 100755
> --- a/configure
> +++ b/configure
> @@ -3525,19 +3525,6 @@ if compile_prog "" "" ; then
>     iovec=yes
>   fi
>   
> -##########################################
> -# preadv probe
> -cat > $TMPC <<EOF
> -#include <sys/types.h>
> -#include <sys/uio.h>
> -#include <unistd.h>
> -int main(void) { return preadv(0, 0, 0, 0); }
> -EOF
> -preadv=no
> -if compile_prog "" "" ; then
> -  preadv=yes
> -fi
> -
>   ##########################################
>   # fdt probe
>   
> @@ -5742,9 +5729,6 @@ fi
>   if test "$iovec" = "yes" ; then
>     echo "CONFIG_IOVEC=y" >> $config_host_mak
>   fi
> -if test "$preadv" = "yes" ; then
> -  echo "CONFIG_PREADV=y" >> $config_host_mak
> -fi
>   if test "$membarrier" = "yes" ; then
>     echo "CONFIG_MEMBARRIER=y" >> $config_host_mak
>   fi
> diff --git a/meson.build b/meson.build
> index 35a9eddf5cf..c4a66d87793 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1128,6 +1128,8 @@ config_host_data.set('HAVE_PTY_H', cc.has_header('pty.h'))
>   config_host_data.set('HAVE_SYS_IOCCOM_H', cc.has_header('sys/ioccom.h'))
>   config_host_data.set('HAVE_SYS_KCOV_H', cc.has_header('sys/kcov.h'))
>   
> +config_host_data.set('CONFIG_PREADV', cc.has_function('preadv', prefix: '#include <sys/uio.h>'))
> +
>   ignored = ['CONFIG_QEMU_INTERP_PREFIX'] # actually per-target
>   arrays = ['CONFIG_AUDIO_DRIVERS', 'CONFIG_BDRV_RW_WHITELIST', 'CONFIG_BDRV_RO_WHITELIST']
>   strings = ['HOST_DSOSUF', 'CONFIG_IASL']
> @@ -2411,7 +2413,7 @@ summary_info += {'PIE':               get_option('b_pie')}
>   summary_info += {'static build':      config_host.has_key('CONFIG_STATIC')}
>   summary_info += {'malloc trim support': has_malloc_trim}
>   summary_info += {'membarrier':        config_host.has_key('CONFIG_MEMBARRIER')}
> -summary_info += {'preadv support':    config_host.has_key('CONFIG_PREADV')}
> +summary_info += {'preadv support':    config_host_data.get('CONFIG_PREADV')}
>   summary_info += {'fdatasync':         config_host.has_key('CONFIG_FDATASYNC')}
>   summary_info += {'madvise':           config_host.has_key('CONFIG_MADVISE')}
>   summary_info += {'posix_madvise':     config_host.has_key('CONFIG_POSIX_MADVISE')}
> 

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Thanks,

Paolo