[libc++] Sync the filesystem clock_gettime handling with chrono for OpenBSD

[brad0]

Copy the same OS checks for clock_gettime from chrono to filesystem and
tweak the comment as Hurd is in the same situation.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Brad Smith (brad0)

Changes

Copy the same OS checks for clock_gettime from chrono to filesystem and
tweak the comment as Hurd is in the same situation.

---

Full diff: https://github.com/llvm/llvm-project/pull/92675.diff

2 Files Affected:

• (modified) libcxx/src/chrono.cpp (+2-2)
• (modified) libcxx/src/filesystem/filesystem_clock.cpp (+3-1)

diff --git a/libcxx/src/chrono.cpp b/libcxx/src/chrono.cpp
index e7d6dfbc22924..e8ebb67284bbb 100644
--- a/libcxx/src/chrono.cpp
+++ b/libcxx/src/chrono.cpp
@@ -31,8 +31,8 @@
 #  include <sys/time.h> // for gettimeofday and timeval
 #endif
 
-// OpenBSD does not have a fully conformant suite of POSIX timers, but
-// it does have clock_gettime and CLOCK_MONOTONIC which is all we need.
+// GNU Hurd and OpenBSD do not implement a fully conformant suite of POSIX timers, but
+// they do have clock_gettime and CLOCK_MONOTONIC which are all we need.
 #if defined(__APPLE__) || defined(__gnu_hurd__) || defined(__OpenBSD__) || (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
 #  define _LIBCPP_HAS_CLOCK_GETTIME
 #endif
diff --git a/libcxx/src/filesystem/filesystem_clock.cpp b/libcxx/src/filesystem/filesystem_clock.cpp
index e13b2853e367c..a120be14978a3 100644
--- a/libcxx/src/filesystem/filesystem_clock.cpp
+++ b/libcxx/src/filesystem/filesystem_clock.cpp
@@ -29,7 +29,9 @@
 #  include <sys/time.h> // for gettimeofday and timeval
 #endif
 
-#if defined(__APPLE__) || defined(__gnu_hurd__) || (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
+// GNU Hurd and OpenBSD do not implement a fully conformant suite of POSIX timers, but
+// they do have clock_gettime and CLOCK_MONOTONIC which are all we need.
+#if defined(__APPLE__) || defined(__gnu_hurd__) || defined(__OpenBSD__) || (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
 #  define _LIBCPP_HAS_CLOCK_GETTIME
 #endif
 

[mordante]

In general we like to have a CI runner to test platform specific behaviour. Do you intent to add a GNU Hurd runner? (This change is small and innocent, but without CI tests there is no guarantee there won't be regressions.)

Can you make the commit message a bit more descriptive. Something along the lines of
[libc++] Add GNU Hurd clock_gettime support seems better describing the goal of the change.