Remove incorrect explicit instantiation declarations for valarray

[rsmith]

Summary

libc++ ABI v1 provides three valarray symbols as part of the shared library:

valarray<size_t>::valarray(size_t)
valarray<size_t>::~valarray()
valarray<size_t>::resize(size_t, size_t)

The first two of these appear to be intended to be removed in V2 of the ABI: they're attributed _LIBCPP_HIDE_FROM_ABI_AFTER_V1, and looking through the commit history it appears that the intention is that these symbols from the library are not used even when building using the V1 ABI. However, there are explicit instantiation declarations for all three symbols in the header, which are wrong as we do not intend to find an instantiation of these functions that is provided elsewhere.

(A recent change to clang to properly diagnose explicit instantiation declarations of internal linkage functions -- required by [temp.explicit]p13 -- had to be rolled back because it diagnosed these explicit instantiations.)

Remove the explicit instantiation declarations, and remove the explicit instantiation definitions for V2 of the libc++ ABI onwards.

[ldionne]

src/valarray.cpp

13

Can you add a comment explaining why we're doing this here?

[rsmith]

src/valarray.cpp

13

Done, but I'm not sure why these are removed from the V2 ABI so I'm afraid it's a little vague.

[rsmith]

Committed as r359243.

[ldionne]

src/valarray.cpp

13

Well, they're removed because they will never be used (since there's no explicit instantiation declaration), right? My understanding is that the only reason for providing them in ABI v1 is to avoid removing symbols (and code) that already-compiled binaries might depend on, however newly compiled code will never use it. If that is incorrect, then I did not understand this patch.

[rsmith]

src/valarray.cpp

13

Well... I agree, but that doesn't really explain why we don't want these to be part of the V2 ABI, which is what I think I'd want to know as a reader of this code. (Why were these deemed suitable for inclusion in the V1 ABI but not in the V2 ABI? Why is valarray<size_t>::resize still part of the V2 ABI?)

[ldionne]

src/valarray.cpp

13

How about we remove valarray from the dylib completely in ABI v2? Is there evidence that we're gaining from including it in the dylib?

include/valarray

private:
     const _Up*
     end(const valarray<_Up>& __v);
 
     _LIBCPP_INLINE_VISIBILITY
     void __clear(size_t __capacity);
     valarray& __assign_range(const value_type* __f, const value_type* __l);
 };
 
-_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS valarray<size_t>::valarray(size_t))
-_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS valarray<size_t>::~valarray())
 _LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void valarray<size_t>::resize(size_t, size_t))
 
 template <class _Op, class _Tp>
 struct _UnaryOp<_Op, valarray<_Tp> >
 {
     typedef typename _Op::result_type result_type;
     typedef _Tp value_type;
 

lib/abi/x86_64-apple-darwin.v2.abilist

 {'is_defined': True, 'name': '__ZNSt3__28numpunctIwED0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__28numpunctIwED1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__28numpunctIwED2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__28time_getIcNS_19istreambuf_iteratorIcNS_11char_traitsIcEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__28time_getIwNS_19istreambuf_iteratorIwNS_11char_traitsIwEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__28time_putIcNS_19ostreambuf_iteratorIcNS_11char_traitsIcEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__28time_putIwNS_19ostreambuf_iteratorIwNS_11char_traitsIwEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__28valarrayImE6resizeEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__28valarrayImEC1Em', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__28valarrayImEC2Em', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__28valarrayImED1Ev', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__28valarrayImED2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__29__num_getIcE17__stage2_int_loopEciPcRS2_RjcRKNS_12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEEPjRSD_PKc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__29__num_getIcE17__stage2_int_prepERNS_8ios_baseERc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__29__num_getIcE19__stage2_float_loopEcRbRcPcRS4_ccRKNS_12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEEPjRSE_RjS4_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__29__num_getIcE19__stage2_float_prepERNS_8ios_baseEPcRcS5_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__29__num_getIwE17__stage2_int_loopEwiPcRS2_RjwRKNS_12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEEPjRSD_PKw', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__29__num_getIwE17__stage2_int_prepERNS_8ios_baseERw', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__29__num_getIwE19__stage2_float_loopEwRbRcPcRS4_wwRKNS_12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEEPjRSE_RjPw', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__29__num_getIwE19__stage2_float_prepERNS_8ios_baseEPwRwS5_', 'type': 'FUNC'}

src/valarray.cpp

 //===------------------------ valarray.cpp --------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "valarray"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+// These two symbols are part of the v1 ABI but not part of the >=v2 ABI.
+#if _LIBCPP_ABI_VERSION == 1
 template valarray<size_t>::valarray(size_t);
 template valarray<size_t>::~valarray();
+#endif
+
 template void valarray<size_t>::resize(size_t, size_t);
 
 void
 gslice::__init(size_t __start)
 {
     valarray<size_t> __indices(__size_.size());
     size_t __k = __size_.size() != 0;
     for (size_t __i = 0; __i < __size_.size(); ++__i)