Always have math functions but with weak linking attribute if we can
#577
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Amjad50
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For some reason, windows building fails, and the error is confusing, it can't find some symbols that are unrelated to what have changed. |
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Can you check this @Amanieu? Thanks |
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We're currently waiting for fixes on the rustc side before work on compiler-builtins can continue: rust-lang/rust#121552 |
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Ah, thanks for the info. |
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CI should be fixed now, can you rebase? |
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Thanks, Builds now |
Amanieu
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Mar 28, 2024
Amanieu
reviewed
Mar 29, 2024
src/math.rs
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| all(target_arch = "xtensa", target_os = "none"), | ||
| all(target_vendor = "fortanix", target_env = "sgx") | ||
| ))] | ||
| #[cfg(not(target_os = "windows"))] |
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Suggested change
| #[cfg(not(target_os = "windows"))] | |
| #[cfg_attr(all(not(windows), not(target_vendor = "apple")), weak)] |
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We do have this already inside no_mangle, so probably just remove the cfg completely is a better choice
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No, we shouldn't provide the math intrinsics at all on windows/apple targets since weak linkage doesn't work properly. On those target we should always be getting these symbols from libc. The only exception is lgamma_r and lgammaf_r which are missing on MSVC targets.
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then you probably mean to use cfg and not cfg_attr? The suggested change is to use cfg_attr(weak) for non windows/apple
This is a replacement for rust-lang/libm#290 This fixes crashes during compilations for targets that don't have math symbols by default. So, we will provide them libm symbols, but mark it as `weak` (if its supported), so that the linker will choose the system builtin functions, since those are sometimes more optimized. If the linker couldn't find those, it will go with `libm` implementation.
taiki-e
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Apr 17, 2024
```
error[E0658]: use of unstable library feature 'proc_macro_byte_character'
--> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2-1.0.80/src/wrapper.rs:871:21
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871 | proc_macro::Literal::byte_character(byte)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: see issue #115268 <rust-lang/rust#115268> for more information
= help: add `#![feature(proc_macro_byte_character)]` to the crate attributes to enable
= note: this compiler was built on 2024-03-21; consider upgrading it if it is out of date
error[E0658]: use of unstable library feature 'proc_macro_c_str_literals'
--> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2-1.0.80/src/wrapper.rs:898:21
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898 | proc_macro::Literal::c_string(string)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: see issue #119750 <rust-lang/rust#119750> for more information
= help: add `#![feature(proc_macro_c_str_literals)]` to the crate attributes to enable
= note: this compiler was built on 2024-03-21; consider upgrading it if it is out of date
```
Also, the latest nightly cannot be used due to rust-lang/compiler-builtins#577.
```
= note: /usr/lib/gcc/avr/5.4.0/../../../avr/lib/avr6/libm.a(addsf3.o): In function `__addsf3':
(.text.avr-libc.fplib+0x2): multiple definition of `__addsf3'
/home/runner/work/portable-atomic/portable-atomic/target/no-std-test/avr-unknown-gnu-atmega2560/debug/deps/libcompiler_builtins-81c93cbf49042e5b.rlib(compiler_builtins-81c93cbf49042e5b.compiler_builtins.3808c58458fddf11-cgu.07.rcgu.o):/home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/compiler_builtins-0.1.109/src/macros.rs:500: first defined here
```
taiki-e
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Apr 17, 2024
rust-lang/compiler-builtins#577 caused regression on no-std hexagon: ``` error: symbol 'fma' is already defined error: symbol 'fmax' is already defined ```
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This is a replacement for rust-lang/libm#290
This fixes crashes during compilations for targets that don't have math symbols by default.
So, we will provide them libm symbols, but mark it as
weak(if its supported), so that the linker will choose the system builtin functions, since those are sometimes more optimized.If the linker couldn't find those, it will go with
libmimplementation.