The fstype argument to the mount system call can be null. To see an
example run "strace -e trace=mount unshare -m":
```
mount("none", "/", NULL, MS_REC|MS_PRIVATE, NULL) = 0
...
```
Future improvement: make plain error notes actually render as notes
rather than errors, but keep them as errors for the case of
sub-compilation errors, e.g. when compiler-rt has compilation errors.
The previous definition depends on a non-lang-spec-compliant memory
layout for packed structs, which happens to trigger #11989 in stage2.
This commit changes the struct to be an extern struct with an
align(4) field. However, stage1 cannot handle this, so conditional
compilation logic is used to select different struct definitions
depending on stage1 vs stage2.
This works around #11989 but does not solve the underlying problem -
putting an extern union inside a packed struct will still trigger the
assert.
After this, both stage1 and stage2 std lib tests run assertion-clean
with a debug LLVM 13.
This follows LLVM14's lead on vector alignment, which computes byte
count based on the length premultiplied by bits.
This commit also disables behavior tests regressed by LLVM 14, only for
stage1. stage2 fortunately does not trip the regression.
LLVM 14 makes it so that a RHS of saturating shift left produces a
poison value if the value is greater than the number of bits of the LHS.
Zig now emits code that will check if this is the case and select a
saturated LHS value in such case, matching Zig semantics.
Notable changes:
`_i386`, `_i486`, and `_i686` are renamed to `i386`, `i486`,
and `i686` respectively. `std.zig.fmtId` is enhanced to support
formatting `i386` as `@"i386"`.
Some CPU features which are actually CPU models have been
properly flattened, such as `apple_a12`, `apple_a13`, `apple_a7`,
`cortex_a78c`, `exynos_m4`, `neoverse_e1`, `neoverse_n1`,
`neoverse_n2`, `neoverse_v1`.
Some CPU features have been added and some have been removed, following
LLVM's lead.
CSky CPU features support is added.
LLVM pointers are transitioning to no longer have types, however, inline
assembly inputs and outputs which accept pointers need to know the
element type. So, inline assembly must be upgraded to add
elementtype(<ty>) annotations.
LLVM 14 deprecated a bunch of C API functions in preparation for opaque
pointer changes. However, they did not actually implement opaque pointer
semantics, so the deprecations are largely masturbatory. I have nothing
against masturbation, I am just busy trying to get the self hosted
compiler done for 0.10.0, so we will come back to this later.
This is a prelude to a more elaborate work which will implement
`-dead_strip` flag - garbage collection of unreachable atoms. Here,
when sorting sections, we also check that the section is actually
populated with some atoms, and if not, we exclude it from the final
linked image. This can happen when we do not import any symbols
from dynamic libraries in which case we will not be populating
the stubs sections or the GOT table, implying we can skip allocating
those sections. Furthermore, we also make a check that a segment
is actually occupied too, with the exception of `__TEXT` segment
which is non-optional given that it wraps the header and load commands
and thus is required by the `dyld` to perform dynamic linking, and
`__PAGEZERO` which is generally non-optional when the linked image
is an executable. For any other segment, if its section count is
zero, we mark it as dead and skip allocating it and generating
a load command for it.
This commit also includes some minor improvements to the linker such
as refactoring of the segment allocating codepaths, skipping
`__PAGEZERO` generation for dylibs, and skipping generation of zero-sized
atoms for special symbols such as `__mh_execute_header` and `___dso_handle`.
These special symbols are only allocated local and global symbol pair
and their VM addresses is set to the start of the `__TEXT` segment,
but no `Atom` is created, as it's not necessary given that they never
carry any machine code.
Finally, we now always force-link against `libSystem` which turns out
to be required for `dyld` to properly handle `LC_MAIN` load command
on older macOS versions such as 10.15.7.
