[libc++] Add "using-if-exists" to timespec_get in modules

[domin144]

Picolibc does not provide timespec_get function. Adding "using-if-exists" attribute fixes the modules.

This is a follow up patch for #78580

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Dominik Wójt (domin144)

Changes

Picolibc does not provide timespec_get function. Adding "using-if-exists" attribute fixes the modules.

This is a follow up patch for #78580

---

Full diff: https://github.com/llvm/llvm-project/pull/78686.diff

3 Files Affected:

• (modified) libcxx/modules/std.compat/ctime.inc (+1-1)
• (modified) libcxx/modules/std/ctime.inc (+1-1)
• (modified) libcxx/test/std/modules/std.compat.pass.cpp (-4)

diff --git a/libcxx/modules/std.compat/ctime.inc b/libcxx/modules/std.compat/ctime.inc
index 92e3403a5e58e27..6e621f494348d74 100644
--- a/libcxx/modules/std.compat/ctime.inc
+++ b/libcxx/modules/std.compat/ctime.inc
@@ -24,5 +24,5 @@ export {
   using ::mktime;
   using ::strftime;
   using ::time;
-  using ::timespec_get;
+  using ::timespec_get _LIBCPP_USING_IF_EXISTS;
 } // export
diff --git a/libcxx/modules/std/ctime.inc b/libcxx/modules/std/ctime.inc
index c407ffc35e3fe3c..c98cb28e649b85e 100644
--- a/libcxx/modules/std/ctime.inc
+++ b/libcxx/modules/std/ctime.inc
@@ -24,5 +24,5 @@ export namespace std {
   using std::mktime;
   using std::strftime;
   using std::time;
-  using std::timespec_get;
+  using std::timespec_get _LIBCPP_USING_IF_EXISTS;
 } // namespace std
diff --git a/libcxx/test/std/modules/std.compat.pass.cpp b/libcxx/test/std/modules/std.compat.pass.cpp
index 9a2f330d722edde..a33ed3b6b64533a 100644
--- a/libcxx/test/std/modules/std.compat.pass.cpp
+++ b/libcxx/test/std/modules/std.compat.pass.cpp
@@ -11,10 +11,6 @@
 // UNSUPPORTED: libcpp-has-no-std-modules
 // UNSUPPORTED: clang-modules-build
 
-// picolibc does not provide the required timespec_get function, and the
-// "using-if-exists" mechanism apparently did not work here.
-// XFAIL: LIBCXX-PICOLIBC-FIXME
-
 // A minimal test to validate import works.
 
 import std.compat;

[domin144]

After rebasing the patch I re-run the tests and realized the test is skipped now. Not sure why, and if this is intentional.
Still, I propose the patch as is, as this fixed the tests when they were run.

[domin144]

Ok, I can see, that now the module tests have to be enabled with set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") in Armv7M-picolibc.cmake.
I tried it, but found, that a more recent version of cmake and ninja is required than those provided with ubuntu 22.04. With those updated, the tests pass.
I checked the logs of the buildkite run and I can see the picolibc tests are run with older versions of cmake and ninja. I am not enabling the module tests in Armv7M-picolibc.cmake for now.

[mordante]

Ok, I can see, that now the module tests have to be enabled with set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") in Armv7M-picolibc.cmake. I tried it, but found, that a more recent version of cmake and ninja is required than those provided with ubuntu 22.04. With those updated, the tests pass. I checked the logs of the buildkite run and I can see the picolibc tests are run with older versions of cmake and ninja. I am not enabling the module tests in Armv7M-picolibc.cmake for now.

The patches to make modules work with older CMake versions have been reverted. I expect I can reland that patch soon. After that you can rebase this patch on main again and we can test it again.

[mordante]

I've just relanded the dependencies for this patch. Could you rebase this patch to see whether the CI is green?

[domin144]

Thanks for an update. I rebased and I can see the picolibc tests passed.

[mordante]

Thanks! Great to see Picolib working for modules! Since we're getting close the branching I'll directly merge the patch.