The Embedded Swift concurrency library needs a way to exit the program
at the end of async main. The existing implementation calls through a
_swift_exit() function to the POSIX/C exit(). Enshrine _swift_exit()
as part of the Platform Abstraction Layer, with the same signature
(albeit in C), and implement it in the PAL-on-POSIX library as a call
through to exit().
The bridging PCH created by the driver uses a temporary directory,
which introduces nondeterminism into the results. We don't need to
precompile this tiny header, so turn off the precompiled bridging
header.
Fixes rdar://172741975
rdar://158239258
This change adds logic in the compiler to compute malloc type ids and emit them together with typed allocation calls. It also adds the new runtime function swift_allocObjectTyped, which calls typed malloc.
The new library, swiftEmbeddedPlatformPOSIX, implements all of the
_swift_XYZ functions needed to support Embedded Swift as shims on top
of a POSIX system that provides posix_memalign, free, putchar, and so
on. This offers an easier way to bridge between the prior ad hoc
requirements of Embedded Swift and the newer platform abstraction
layer.
Part of rdar://164057124
Embedded Swift depends on a number of functions from the platform,
including posix_memalign, free, and arc4random_buf. While these
dependencies are documented, they aren't documented in a manner that
makes them easy to implement. Additionally, most of these are C
library functions that may or may not be available, and can have
requirements that are more stringent than Embedded Swift actually
requires.
Try to address both problems at once by introducing a new header,
`swift/EmbeddedPlatform.h`, that provides a new set of C declarations
for functions that need to be provided by a platform. For
each function, we provide documentation on what it does, what Embedded
Swift facilities will end up using it (e.g.,
`_swift_generateRandomHashSeed` is needed for seeding the hash
functions used for `Set` and `Dictionary`, among other things), and
some guidance on how to implement it---including those cases where
directly calling an existing C standard library or POSIX function will
suffice.
There is a new CMake option, SWIFT_USE_SWIFT_EMBEDDED_PLATFORM, that
enables the use of these entrypoints in the Embedded Swift runtime. It
is currently disabled, because enabling it would break existing
clients of Embedded Swift. We're looking for a way to stage this in.
Addresses rdar://164057124.
Doug Gregor
Dario Rexin