@llvm/pr-subscribers-libcxx

Author: Victor Campos (vhscampos)

diff --git a/libcxx/include/__config b/libcxx/include/__config
index 77a71b6cf1cae..ab87ed4787b84 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1027,8 +1027,12 @@ typedef __char32_t char32_t;
 #    else
 #      define _LIBCPP_HAS_C8RTOMB_MBRTOC8 0
 #    endif
-#  else
-#    define _LIBCPP_HAS_C8RTOMB_MBRTOC8 0
+#  elif defined (_LIBCPP_PICOLIBC_PREREQ)
+#    if _LIBCPP_PICOLIBC_PREREQ(1, 8, 9) && defined(__cpp_char8_t)
+#      define _LIBCPP_HAS_C8RTOMB_MBRTOC8 1
+#    else
+#      define _LIBCPP_HAS_C8RTOMB_MBRTOC8 0
+#    endif
 #  endif
 
 // There are a handful of public standard library types that are intended to
diff --git a/libcxx/include/__configuration/platform.h b/libcxx/include/__configuration/platform.h
index f3c199dee172b..4f581a352038f 100644
--- a/libcxx/include/__configuration/platform.h
+++ b/libcxx/include/__configuration/platform.h
@@ -47,6 +47,10 @@
 //       user code. Move code paths that need _NEWLIB_VERSION to another customization mechanism.
 #if __has_include(<picolibc.h>)
 #  include <picolibc.h>
+#  define _LIBCPP_PICOLIBC_VERSION_INT(maj, min, patch) (maj * 10000 + min * 100 + patch)
+#  define _LIBCPP_PICOLIBC_PREREQ(maj, min, patch)                                                                     \
+    _LIBCPP_PICOLIBC_VERSION_INT(__PICOLIBC__, __PICOLIBC_MINOR__, __PICOLIBC_PATCHLEVEL__) >=                         \
+        _LIBCPP_PICOLIBC_VERSION_INT(maj, min, patch)
 #endif
 
 #ifndef __BYTE_ORDER__

✅ With the latest revision this PR passed the C/C++ code formatter.

@philnik777 I don't understand the two suggestions you made. Can you please give more details? Thank you

@philnik777 I don't understand the two suggestions you made. Can you please give more details? Thank you

_LIBCPP_HAS_C8RTOMB_MBRTOC8 is currently false if we don't know whether a library provides it or not. IMO we should assume it's available unless we know for a fact it's not. With Clang we don't care at all whether it's available, since we have _LIBCPP_USING_IF_EXISTS, so we can just always define _LIBCPP_HAS_C8RTOMB_MBRTOC8 to true in that case.

I've refactored in a way that the macro is true "by default" as you suggested.

However, with regards to always setting it to true if compiling with clang, that causes a libcxx test to fail (link:

The value of macro TEST_HAS_NO_C8RTOMB_MBRTOC8 depends on _LIBCPP_HAS_C8RTOMB_MBRTOC8 (link:

I couldn't think of a way to modify the test in order to have the macro true for clang.

I've refactored in a way that the macro is true "by default" as you suggested.

However, with regards to always setting it to true if compiling with clang, that causes a libcxx test to fail (link:

llvm-project/libcxx/test/std/strings/c.strings/cuchar.compile.pass.cpp

Line 26 in 372d86d

#if !defined(TEST_HAS_NO_C8RTOMB_MBRTOC8)

)

The value of macro TEST_HAS_NO_C8RTOMB_MBRTOC8 depends on _LIBCPP_HAS_C8RTOMB_MBRTOC8 (link:

llvm-project/libcxx/test/support/test_macros.h

Line 453 in 372d86d

# define TEST_HAS_NO_C8RTOMB_MBRTOC8

), so if we always set it to true for clang, this test fails if the functions aren't defined in the C library.

I couldn't think of a way to modify the test in order to have the macro true for clang.

We should probably just XFAIL the test on platforms that haven't fully implemented the interface. @ldionne any thoughts?

Handling every case is brittle because I can't run the CI jobs locally, e.g. on AIX. Sorry for the high traffic.