* Reuse bytes of async function frames when non-async functions
make `noasync` calls. This prevents explosive stack growth.
* Zig now passes a stack size argument to the linker when linking ELF
binaries. Linux ignores this value, but it is available as a program
header called GNU_STACK. I prototyped some code that memory maps
extra space to the stack using this program header, but there was
still a problem when accessing stack memory very far down. Stack
probing is needed or not working or something. I also prototyped
using `@newStackCall` to call main and that does work around the
issue but it also brings its own issues. That code is commented out
for now in std/special/start.zig. I'm on a plane with no Internet,
but I plan to consult with the musl community for advice when I get a
chance.
* Added `noasync` to a bunch of function calls in std.debug. It's very
messy but it's a workaround that makes stack traces functional with
evented I/O enabled. Eventually these will be cleaned up as the root
bugs are found and fixed. Programs built in blocking mode are
unaffected.
* Lowered the default stack size of std.io.InStream (for the async
version) to 1 MiB instead of 4. Until we figure out how to get
choosing a stack size working (see 2nd bullet point above), 4 MiB
tends to cause segfaults due to stack size running out, or usage of
stack memory too far apart, or something like that.
* Default thread stack size is bumped from 8 MiB to 16 to match the
size we give for the main thread. It's planned to eventually remove
this hard coded value and have Zig able to determine this value
during semantic analysis, with call graph analysis and function
pointer annotations and extern function annotations.
The comment added by this commit is copied here:
For macOS stack traces, we want to avoid having to parse the compilation unit debug
info. As long as each debug info file has a path independent of the compilation unit
directory (DW_AT_comp_dir), then we never have to look at the compilation unit debug
info. If we provide an absolute path to LLVM here for the compilation unit debug info,
LLVM will emit DWARF info that depends on DW_AT_comp_dir. To avoid this, we pass "."
for the compilation unit directory. This forces each debug file to have a directory
rather than be relative to DW_AT_comp_dir. According to DWARF 5, debug files will
no longer reference DW_AT_comp_dir, for the purpose of being able to support the
common practice of stripping all but the line number sections from an executable.
closes#2700
When `@frameSize` is never called, and `@asyncCall` on a runtime-known
pointer is never used, no prefix data for async functions is needed.
Related: #3160
* `await @asyncCall` generates better code. See #3065
* `@asyncCall` works with a real `@Frame(func)` in addition to
a byte slice. Closes#3072
* `@asyncCall` allows passing `{}` (a void value) as the result
pointer, which uses the result location inside the frame.
Closes#3068
* support `await @asyncCall` on a non-async function. This is in
preparation for safe recursion (#1006).
