[libc++] tests with picolibc: Fix iterator diff_type to std::streamoff

[domin144]

The hardcoded value of long int was not valid for newlib and picolibc.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Dominik Wójt (domin144)

Changes

The hardcoded value of long int was not valid for newlib and picolibc.

---

Full diff: https://github.com/llvm/llvm-project/pull/74072.diff

1 Files Affected:

• (modified) libcxx/test/std/iterators/iterator.primitives/iterator.traits/cxx20_iterator_traits.compile.pass.cpp (+1-7)

diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/cxx20_iterator_traits.compile.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/cxx20_iterator_traits.compile.pass.cpp
index f56750bb495e15f..3f8c9c2ad8d0221 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/cxx20_iterator_traits.compile.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/cxx20_iterator_traits.compile.pass.cpp
@@ -11,11 +11,6 @@
 // This test uses iterator types from std::filesystem
 // XFAIL: availability-filesystem-missing
 
-// std::same_as<typename Traits::difference_type, DiffType> failed.
-// The former was long and the latter was long long.
-// Possibly related to "using streamoff = long int" in ios.h.
-// XFAIL: LIBCXX-PICOLIBC-FIXME
-
 // template<class T>
 // struct iterator_traits;
 
@@ -152,8 +147,7 @@ static_assert(testIOIterator<std::insert_iterator<std::vector<int>>, std::output
 static_assert(testConst<std::istream_iterator<int, char>, std::input_iterator_tag, int>());
 
 #if !defined(TEST_HAS_NO_LOCALIZATION)
-// libc++-specific since pointer type is unspecified:
-LIBCPP_STATIC_ASSERT(test<std::istreambuf_iterator<char>, std::input_iterator_tag, char, long long, char, char*>());
+static_assert(test<std::istreambuf_iterator<char>, std::input_iterator_tag, char, std::streamoff, char, char*>());
 static_assert(test<std::move_iterator<int*>, std::random_access_iterator_tag, int, std::ptrdiff_t, int&&, int*>());
 static_assert(testIOIterator<std::ostream_iterator<int, char>, std::output_iterator_tag>());
 static_assert(testIOIterator<std::ostreambuf_iterator<int, char>, std::output_iterator_tag>());

[domin144]

@ldionne @zoecarver

The proposed check is no longer libc++ specific. It follows this derivation:

std::iterator_traits<std::istreambuf_iterator<char>>::difference_type
    = std::istreambuf_iterator<char>::difference_type
    = typename Traits::off_type (Traits = std::char_traits<char>)
    = std::char_traits<char>::off_type
    = std::streamoff

Further is libc++ specific. std::streamoff is defined in libcxx/include/__fwd/ios.h

    #if defined(_NEWLIB_VERSION)
    // On newlib, off_t is 'long int'
    using streamoff = long int; // for char_traits in <string>
    #else
    using streamoff = long long; // for char_traits in <string>
    #endif

As an alternative, the ifdefs from ios.h could be reproduced in the test, making it libc++ specific again.

[ldionne]

LGTM, thanks for the clean up.

[ldionne]

Please rebase onto main and push again, it'll trigger the CI again. I just fixed an issue on GCC.

[github-actions]

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

[ldionne]

LGTM, pending CI.