Commit 3014a0d5f1dcbcfdcec3852ffd54f3c589fe3e83 added calling convention
validation, but left out thumb and thumbeb from the archs that can use the
ARM-specific calling conventions. This plus
a8a7f15106abef7c647d4de572a04b77ce048dd6 made compilation fail for thumb
targets.
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.
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.
The constant value lowering for unions was missing a check for whether
the payload was itself an unnamed struct. Lowerings of other types
already handle this case.
closes#11971
Zig guarantees the memory layout of f16, f32, f64, f80, and f128 which
means for generic function purposes, values of these types need to be
compared on the basis of their bits in memory. This means nan-packing
can be used with generic functions, for example.
For comptime_float, the sign is observable, whether it is nan is
observable, but not any more kinds of bit patterns are observable.
This fixes the std.fmt tests that check printing "-nan".
