[libc++] Do not forward-declare syncstream outside experimental #82511
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@llvm/pr-subscribers-libcxx Author: Louis Dionne (ldionne) ChangesWe only define the classes in <syncstream> when experimental library features are enabled, but we would forward-declare them in <iosfwd> even when they are disabled. This led to confusing error messages about being unable to instantiate an undefined template. Full diff: https://github.com/llvm/llvm-project/pull/82511.diff 1 Files Affected:
diff --git a/libcxx/include/iosfwd b/libcxx/include/iosfwd
index e28998d004156d..728700853fb331 100644
--- a/libcxx/include/iosfwd
+++ b/libcxx/include/iosfwd
@@ -143,7 +143,7 @@ typedef fpos<mbstate_t> u8streampos;
typedef fpos<mbstate_t> u16streampos;
typedef fpos<mbstate_t> u32streampos;
-#if _LIBCPP_STD_VER >= 20
+#if _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_SYNCSTREAM)
template <class _CharT, class _Traits = char_traits<_CharT>, class _Allocator = allocator<_CharT>>
class basic_syncbuf;
@@ -161,7 +161,7 @@ using osyncstream = basic_osyncstream<char>;
using wosyncstream = basic_osyncstream<wchar_t>;
# endif
-#endif // _LIBCPP_STD_VER >=20
+#endif // _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_SYNCSTREAM)
// Include other forward declarations here
template <class _Tp, class _Alloc = allocator<_Tp> >
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philnik777
approved these changes
Feb 21, 2024
We only define the classes in <syncstream> when experimental library features are enabled, but we would forward-declare them in <iosfwd> even when they are disabled. This led to confusing error messages about being unable to instantiate an undefined template.
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✅ With the latest revision this PR passed the C/C++ code formatter. |
mordante
approved these changes
Feb 28, 2024
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We only define the classes in
<syncstream>when experimental library features are enabled, but we would forward-declare them in<iosfwd>even when they are disabled. This led to confusing error messages about being unable to instantiate an undefined template.