Currently we read many small chunks from the process we're backtracing.
If it so happens that it's the local process, that isn't really a big
problem, but if it's a remote process, especially on Linux where we have
to use the memory server, it's probably a little slow.
Fix by adding a caching layer.
rdar://117681625
This adds a new binary, `swift-backtrace-static`, to the build. The runtime
will not by default use this binary as the backtracer, but if you want to
statically link your own binaries against the standard library you can copy
`swift-backtrace-static` rather than `swift-backtrace` alongside your binary,
naming it `swift-backtrace`, and the runtime should find and use it, which
will mean you don't need to have `libswiftCore.so` et al installed.
rdar://115278959
We were using a regular expression to scan `/proc/<pid>/maps`, but we
shouldn't really do that because it breaks non-bootstrapped builds.
rdar://110452324
Use the new module structure rather the old SwiftShims header. This
is much cleaner and lets us include operating system headers to get
the relevant definitions where possible.
Add code to support ELF and DWARF, including decompression using
zlib, zstd and liblzma if those turn out to be required and available.
rdar://110261712
Using `SwiftShims` is undesirable - it creates all kinds of build issues,
and means shipping the `_SwiftBacktracing.h` header in the SDK, which is
not necessary.
While we're doing this, add the necessary definitions for reading ELF
and DWARF information.
rdar://110261712
On ARM Windows, we need MARMASM to assemble the context capture code,
but CMake doesn't support MARMASM until version 3.26, which isn't yet
released.
(Confusingly it appears to have partial but non-working support in the
present versions.)
rdar://106284325
Added some extra code to AddSwiftStdlib.cmake so executable targets can
specify target SDKs the same way libraries currently can.
Updated the Backtracing targets to specify just OS X for now.
Adds a new swift_Backtracing library, with a corresponding _Backtracing
module, to the build. Also add some tests.
This is not public API at this point, but will be used by the external
backtracing program, `swift-backtrace`.
rdar://104336548
