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std: Add compatibility with android-9

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The Gecko folks currently use Android API level 9 for their builds, so they're
requesting that we move back our minimum supported API level from 18 to 9. Turns
out, ABI-wise at least, there's not that many changes we need to take care of.
The `ftruncate64` API appeared in android-12 and the `log2` and `log2f` APIs
appeared in android-18. We can have a simple shim for `ftruncate64` which falls
back on `ftruncate` and the `log2` function can be approximated with just
`ln(f) / ln(2)`.

This should at least get the standard library building on API level 9, although
the tests aren't quite happening there just yet. As we seem to be growing a
number of Android compatibility shims, they're now centralized in a common
`sys::android` module.
This commit is contained in:
Alex Crichton 2016-04-25 13:39:05 -07:00
parent cfae4dea87
commit c31e2e77ed
5 changed files with 138 additions and 36 deletions
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32
src/libstd/sys/unix/mod.rs
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@ -31,6 +31,7 @@ use ops::Neg;
#[macro_use]
pub mod weak;
pub mod android;
pub mod backtrace;
pub mod condvar;
pub mod ext;
@ -91,37 +92,8 @@ pub fn init() {
unsafe fn reset_sigpipe() {}
}
// Currently the minimum supported Android version of the standard library is
// API level 18 (android-18). Back in those days [1] the `signal` function was
// just an inline wrapper around `bsd_signal`, but starting in API level
// android-20 the `signal` symbols was introduced [2]. Finally, in android-21
// the API `bsd_signal` was removed [3].
//
// Basically this means that if we want to be binary compatible with multiple
// Android releases (oldest being 18 and newest being 21) then we need to check
// for both symbols and not actually link against either.
//
// Note that if we're not on android we just link against the `android` symbol
// itself.
//
// [1]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
// /android-18/arch-arm/usr/include/signal.h
// [2]: https://chromium.googlesource.com/android_tools/+/fbd420/ndk_experimental
// /platforms/android-20/arch-arm
// /usr/include/signal.h
// [3]: https://chromium.googlesource.com/android_tools/+/20ee6d/ndk/platforms
// /android-21/arch-arm/usr/include/signal.h
#[cfg(target_os = "android")]
unsafe fn signal(signum: libc::c_int,
handler: libc::sighandler_t) -> libc::sighandler_t {
weak!(fn signal(libc::c_int, libc::sighandler_t) -> libc::sighandler_t);
weak!(fn bsd_signal(libc::c_int, libc::sighandler_t) -> libc::sighandler_t);
let f = signal.get().or_else(|| bsd_signal.get());
let f = f.expect("neither `signal` nor `bsd_signal` symbols found");
f(signum, handler)
}
pub use sys::android::signal;
#[cfg(not(target_os = "android"))]
pub use libc::signal;