* libc: implement common `abs` for various integer sizes
* libc: move imaxabs to inttypes.zig and don't use cInclude
* libc: delete `fabs` c implementations because already implemented in compiler_rt
* libc: export functions depending on the target libc
Previously all the functions that were exported were handled equally,
though some may exist and some not inside the same file. Moving the
checks inside the file allows handling different functions differently
* remove empty ifs in inttypes
Co-authored-by: Alex Rønne Petersen <alex@alexrp.com>
* remove empty ifs in stdlib
Co-authored-by: Alex Rønne Petersen <alex@alexrp.com>
* libc: use `@abs` for the absolute value calculation
---------
Co-authored-by: Alex Rønne Petersen <alex@alexrp.com>
* Introduce common `bzero` libc implementation.
* Update test name according to review
Co-authored-by: Linus Groh <mail@linusgroh.de>
* address code review
- import common implementation when musl or wasi is included
- don't use `c_builtins`, use `@memset`
* bzero calling conv to .c
* Apply review
Co-authored-by: Veikka Tuominen <git@vexu.eu>
---------
Co-authored-by: Linus Groh <mail@linusgroh.de>
Co-authored-by: Veikka Tuominen <git@vexu.eu>
This lays the groundwork for #2879. This library will be built and linked when a
static libc is going to be linked into the compilation. Currently, that means
musl, wasi-libc, and MinGW-w64. As a demonstration, this commit removes the musl
C code for a few string functions and implements them in libzigc. This means
that those libzigc functions are now load-bearing for musl and wasi-libc.
Note that if a function has an implementation in compiler-rt already, libzigc
should not implement it. Instead, as we recently did for memcpy/memmove, we
should delete the libc copy and rely on the compiler-rt implementation.
I repurposed the existing "universal libc" code to do this. That code hadn't
seen development beyond basic string functions in years, and was only usable-ish
on freestanding. I think that if we want to seriously pursue the idea of Zig
providing a freestanding libc, we should do so only after defining clear goals
(and non-goals) for it. See also #22240 for a similar case.
crti.o/crtn.o is a legacy strategy for calling constructor functions
upon object loading that has been superseded by the
init_array/fini_array mechanism.
Zig code depends on neither, since the language intentionally has no way
to initialize data at runtime, but alas the Zig linker still must
support this feature since popular languages depend on it.
Anyway, the way it works is that crti.o has the machine code prelude of
two functions called _init and _fini, each in their own section with the
respective name. crtn.o has the machine code instructions comprising the
exitlude for each function. In between, objects use the .init and .fini
link section to populate the function body.
This function is then expected to be called upon object initialization
and deinitialization.
This mechanism is depended on by libc, for example musl and glibc, but
only for older ISAs. By the time the libcs gained support for newer
ISAs, they had moved on to the init_array/fini_array mechanism instead.
For the Zig linker, we are trying to move the linker towards
order-independent objects which is incompatible with the legacy
crti/crtn mechanism.
Therefore, this commit drops support entirely for crti/crtn mechanism,
which is necessary since the other commits in this branch make it
nondeterministic in which order the libc objects and the other link
inputs are sent to the linker.
The linker is still expected to produce a deterministic output, however,
by ignoring object input order for the purposes of symbol resolution.
Whatever was in the frame pointer register prior to clone() will no longer be
valid in the child process, so zero it to protect FP-based unwinders. This is
just an extension of what was already done for i386 and x86_64. Only applied
to architectures where the _start() code also zeroes the frame pointer.
This was a bit trickier than it should be due to symbol conflicts with
zig's compiler-rt implementation. We attempt to use weak linkage in
our compiler-rt, but this does not seem to be working in all cases. I
manually disabled export of the problematic compiler-rt math functions
in order to cross compile musl's libc.so for all targets as input to
`tools/gen_stubs.zig`.
Other than that, this update went fairly smoothly. Quite a few
additional symbols were added to the blacklist in `tools/gen_stubs.zig`
due to recent reorganization of zig's compiler-rt.
GasInfinity