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:
> > > > > 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.
> > warning: -z.* ignored
>
> Doesn't this stop working if binutils starts to use `error: -z.* ignored`?
> Isn't there a way to call `check_linker_flag` only when the target is
> Solaris? Does `LLVM_LINKER_IS_SOLARISLD` work?
> > warning: -z.* ignored
>
> Doesn't this stop working if binutils starts to use `error: -z.* ignored`?
No: `FAIL_REGEX` only adds to error detection, every other condition just
remains as is.
> Isn't there a way to call `check_linker_flag` only when the target is
> Solaris? Does `LLVM_LINKER_IS_SOLARISLD` work?
That would be wrong: this is about working around a GNU `ld` bug. Imagine
adding a new `-z` option to `lld` which either GNU `ld` didn't adopt at all or
only in the latest release. You'd want to reject the use of that option on
earlier GNU `ld` just the same, no Solaris in sight.
As I said: `LINKER_SUPPORTS_Z_RELAX_TRANSTLS` must always be defined because
`Solaris.cpp` is always compiled no matter what the target.
I really don't understand what you're trying to guard against by putting up
roadblock after roadblock for this patch.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D91605/new/
https://reviews.llvm.org/D91605
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