Re: [PATCH v8 09/11] block: check availablity for preadv/pwritev on mac
Sorry to rephrase this, we would like a single binary to work on both macOS 10.15 and macOS 11 as well as on both iOS 13 and iOS 14 while ALSO supporting preadv/pwritev when running on the newer OS. -j On Sat, Jan 23, 2021 at 12:00 PM Joelle van Dyne wrote: > > The problem here is that we would like to compile on macOS 11 and be > able to run the built binaries on macOS 10.15 or lower. Without the > runtime checks, you'll have a crash when calling preadv/pwritev. > > -j > > On Sat, Jan 23, 2021 at 5:53 AM Peter Maydell > wrote: > > > > On Sat, 23 Jan 2021 at 05:03, Joelle van Dyne wrote: > > > > > > macOS 11/iOS 14 added preadv/pwritev APIs. Due to weak linking, configure > > > will succeed with CONFIG_PREADV even when targeting a lower OS version. > > > We therefore need to check at run time if we can actually use these APIs. > > > > If you make the preadv check be a meson.build has_function() > > test, I think (but have not tested) that it ought to correctly > > fail the link in the targeting-lower-OS-version case, because > > meson.build's has_function() implementation for clang > > https://github.com/mesonbuild/meson/blob/bad0e95caec4cf49165572df3cf2edc4832280fa/mesonbuild/compilers/mixins/clang.py#L89 > > adds -Wl,-no-weak-imports when it's building the test-case > > exactly to force that linker visibility obeys the minimum > > version targets for OSX. > > > > If that works I think it would be neater than delaying the > > check to runtime (and it would also mean another test moved > > out of configure and into meson.build, which is the direction > > we're heading anyway). > > > > thanks > > -- PMM
Re: [PATCH v8 09/11] block: check availablity for preadv/pwritev on mac
The problem here is that we would like to compile on macOS 11 and be able to run the built binaries on macOS 10.15 or lower. Without the runtime checks, you'll have a crash when calling preadv/pwritev. -j On Sat, Jan 23, 2021 at 5:53 AM Peter Maydell wrote: > > On Sat, 23 Jan 2021 at 05:03, Joelle van Dyne wrote: > > > > macOS 11/iOS 14 added preadv/pwritev APIs. Due to weak linking, configure > > will succeed with CONFIG_PREADV even when targeting a lower OS version. > > We therefore need to check at run time if we can actually use these APIs. > > If you make the preadv check be a meson.build has_function() > test, I think (but have not tested) that it ought to correctly > fail the link in the targeting-lower-OS-version case, because > meson.build's has_function() implementation for clang > https://github.com/mesonbuild/meson/blob/bad0e95caec4cf49165572df3cf2edc4832280fa/mesonbuild/compilers/mixins/clang.py#L89 > adds -Wl,-no-weak-imports when it's building the test-case > exactly to force that linker visibility obeys the minimum > version targets for OSX. > > If that works I think it would be neater than delaying the > check to runtime (and it would also mean another test moved > out of configure and into meson.build, which is the direction > we're heading anyway). > > thanks > -- PMM
Re: [PATCH v8 09/11] block: check availablity for preadv/pwritev on mac
On Sat, 23 Jan 2021 at 05:03, Joelle van Dyne wrote: > > macOS 11/iOS 14 added preadv/pwritev APIs. Due to weak linking, configure > will succeed with CONFIG_PREADV even when targeting a lower OS version. > We therefore need to check at run time if we can actually use these APIs. If you make the preadv check be a meson.build has_function() test, I think (but have not tested) that it ought to correctly fail the link in the targeting-lower-OS-version case, because meson.build's has_function() implementation for clang https://github.com/mesonbuild/meson/blob/bad0e95caec4cf49165572df3cf2edc4832280fa/mesonbuild/compilers/mixins/clang.py#L89 adds -Wl,-no-weak-imports when it's building the test-case exactly to force that linker visibility obeys the minimum version targets for OSX. If that works I think it would be neater than delaying the check to runtime (and it would also mean another test moved out of configure and into meson.build, which is the direction we're heading anyway). thanks -- PMM
[PATCH v8 09/11] block: check availablity for preadv/pwritev on mac
macOS 11/iOS 14 added preadv/pwritev APIs. Due to weak linking, configure
will succeed with CONFIG_PREADV even when targeting a lower OS version.
We therefore need to check at run time if we can actually use these APIs.
Signed-off-by: Joelle van Dyne
---
block/file-posix.c | 33 +
1 file changed, 33 insertions(+)
diff --git a/block/file-posix.c b/block/file-posix.c
index 666d3e7504..6473f84db8 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1386,17 +1386,50 @@ static int handle_aiocb_flush(void *opaque)
#ifdef CONFIG_PREADV
static bool preadv_present = true;
+static bool preadv_checked;
static ssize_t
qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)
{
+#ifdef CONFIG_DARWIN /* preadv introduced in macOS 11 */
+if (unlikely(!preadv_checked)) {
+if (__builtin_available(macOS 11, iOS 14, watchOS 7, tvOS 14, *)) {
+preadv_checked = true;
+} else {
+preadv_present = false;
+return -ENOSYS;
+}
+}
+/* Now we suppress the availability warning since we use the cached check
*/
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunguarded-availability-new"
+return preadv(fd, iov, nr_iov, offset);
+#pragma clang diagnostic pop
+#else /* CONFIG_DARWIN */
return preadv(fd, iov, nr_iov, offset);
+#endif
}
static ssize_t
qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)
{
+#ifdef CONFIG_DARWIN /* preadv introduced in macOS 11 */
+if (unlikely(!preadv_checked)) {
+if (__builtin_available(macOS 11, iOS 14, watchOS 7, tvOS 14, *)) {
+preadv_checked = true;
+} else {
+preadv_present = false;
+return -ENOSYS;
+}
+}
+/* Now we suppress the availability warning since we use the cached check
*/
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunguarded-availability-new"
+return pwritev(fd, iov, nr_iov, offset);
+#pragma clang diagnostic pop
+#else /* CONFIG_DARWIN */
return pwritev(fd, iov, nr_iov, offset);
+#endif
}
#else
--
2.28.0
