[PATCH] D91605: [sanitizers] Implement GetTls on Solaris

[Rainer Orth via Phabricator via cfe-commits]

ro added inline comments.


================
Comment at: clang/tools/driver/CMakeLists.txt:123
+
+check_linker_flag("-Wl,-z,relax=transtls" LINKER_SUPPORTS_Z_RELAX_TRANSTLS)
----------------
MaskRay wrote:
> ro wrote:
> > MaskRay wrote:
> > > ro wrote:
> > > > MaskRay wrote:
> > > > > GNU ld reports a warning instead of an error when an unknown `-z` is seen. The warning remains a warning even with `--fatal-warnings`.
> > > > > GNU ld reports a warning instead of an error when an unknown `-z` is seen. The warning remains a warning even with `--fatal-warnings`.
> > > > 
> > > > Thanks for reminding me about that misfeature of GNU `ld`.  I guess `check_linker_flags` needs to be updated to handle that.
> > > > In the case at hand, it won't matter either way: the flag is only passed to `ld`, which on Solaris is guaranteed to be the native linker.  Once (if at all) I get around to completing D85309, I can deal with that.  For now, other targets won't see linker warnings about this flag, other than when the flag is used at build time.
> > > OK. Then I guess you can condition this when the OS is Solaris?
> > > OK. Then I guess you can condition this when the OS is Solaris?
> > 
> > I fear not: `LINKER_SUPPORTS_Z_RELAX_TRANSTLS` is tested inside an `if` in `Solaris.cpp`: this code is also compiled on non-Solaris hosts.  Why are you worried about the definition being always present?
> It is not suitable if LINKER_SUPPORTS_Z_RELAX_TRANSTLS returns a wrong result for GNU ld, even if it is not used for non-Solaris. We should make the value correct in other configurations.
> It is not suitable if LINKER_SUPPORTS_Z_RELAX_TRANSTLS returns a wrong result for GNU ld, even if it is not used for non-Solaris. We should make the value correct in other configurations.

Tell the binutils maintainers that ;-)  While I'm still unconcerned about this particular case (it's only used on a Solaris host where `clang` hardcodes the use of `/usr/bin/ld`), I continue to be annoyed by GNU `ld`'s nonsensical (or even outright dangerous) behaviour of accepting every `-z` option.

It took me some wrestling with `cmake` , but now `check_linker_flag` correctly rejects `-z ` flags where GNU `ld` produces the warning.

Some caveats about the implementation:
- `check_cxx_compiler_flag` doesn't support the `FAIL_REGEX` arg, so I had to switch to `check_cxx_source_compiles` instead.
- While it would be more appropriate to add the linker flag under test to `CMAKE_REQUIRED_LINK_OPTIONS`, that is only present since `cmake` 3.14 while LLVM still only requires 3.13.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91605/new/

https://reviews.llvm.org/D91605