motiejus/hermetic_cc_toolchain
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update README re. UBSAN

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Also reorder the code snippets. I wasn't able to fix the relnotes
script to take the reordering into account.
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Motiejus Jakštys 2022-01-26 06:15:42 +02:00
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README.md
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@ -11,13 +11,7 @@ from Bazel.
# Usage # Usage
Add this to `.bazelrc`: Add this to your `WORKSPACE`:
```
build --incompatible_enable_cc_toolchain_resolution
```
And this to your `WORKSPACE`:
``` ```
BAZEL_ZIG_CC_VERSION = "v0.4.0" BAZEL_ZIG_CC_VERSION = "v0.4.0"
@ -37,6 +31,12 @@ zig_register_toolchains(register = [
]) ])
``` ```
And this to `.bazelrc`:
```
build --incompatible_enable_cc_toolchain_resolution
```
The snippet above will download the zig toolchain and register it for the The snippet above will download the zig toolchain and register it for the
following platforms: following platforms:
@ -60,6 +60,19 @@ used, run:
$ bazel query @zig_sdk//... | sed -En '/.*_toolchain$/ s/.*:(.*)_toolchain$/\1/p' $ bazel query @zig_sdk//... | sed -En '/.*_toolchain$/ s/.*:(.*)_toolchain$/\1/p'
``` ```
## UBSAN and "SIGILL: Illegal Instruction"
`zig cc` differs from "mainstream" compilers by [enabling UBSAN by
default][ubsan1]. Which means your program may compile successfully and crash
with:
```
SIGILL: illegal instruction
```
This is by design: it encourages program authors to fix the undefined behavior.
There are [many ways][ubsan2] to find the undefined behavior.
# Known Issues In bazel-zig-cc # Known Issues In bazel-zig-cc
These are the things you may stumble into when using bazel-zig-cc. I am These are the things you may stumble into when using bazel-zig-cc. I am
@ -67,6 +80,8 @@ unlikely to implement them, but patches implementing those will be accepted.
See [Questions & Contributions](#questions-amp-contributions) on how to See [Questions & Contributions](#questions-amp-contributions) on how to
contribute. contribute.
## OSX: sysroot ## OSX: sysroot
For non-trivial programs (and for all darwin/arm64 cgo programs) MacOS SDK may For non-trivial programs (and for all darwin/arm64 cgo programs) MacOS SDK may
@ -199,3 +214,5 @@ the issues promptly.
[git-send-email]: https://git-send-email.io/ [git-send-email]: https://git-send-email.io/
[video]: https://spacepub.space/w/no6jnhHeUrt2E5ST168tRL [video]: https://spacepub.space/w/no6jnhHeUrt2E5ST168tRL
[sysroot]: https://github.com/ziglang/zig/issues/10299#issuecomment-989153750 [sysroot]: https://github.com/ziglang/zig/issues/10299#issuecomment-989153750
[ubsan1]: https://github.com/ziglang/zig/issues/4830#issuecomment-605491606
[ubsan2]: https://github.com/ziglang/zig/issues/5163