<valarray>: slice_array's copy ctor is missing, the same with mask_array, gslice_array, indirect_array

[AlexGuteniev]

Describe the bug
slice_array's copy constructor and assignment operator are missing

Command-line test case

d:\Temp2>type repro.cpp
#include <valarray>
#include <cassert>

int main()
{
        int a1[] = { 0, 1, 2 };
        std::valarray<int> v1(a1, 3);
        std::slice_array<int> s1 = v1[std::slice(1, 1, 1)];
        std::slice_array<int> s2 = v1[std::slice(0, 1, 1)];
        std::slice_array<int> const& s3 = s1 = s2;
        std::slice_array<int> s4 = s3;
        assert(&s1 == &s3);
        assert(&s1 == &s4);
}

d:\Temp2>cl /EHsc /W4 /WX .\repro.cpp
Microsoft (R) C/C++ Optimizing Compiler Version 19.27.29009.1 for x86
Copyright (C) Microsoft Corporation.  All rights reserved.

repro.cpp
Microsoft (R) Incremental Linker Version 14.27.29009.1
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:repro.exe
repro.obj
repro.obj : error LNK2019: unresolved external symbol "public: __thiscall std::slice_array<int>::slice_array<int>(class std::slice_array<int> const &)" (??0?$slice_array@H@std@@QAE@ABV01@@Z) referenced in function _main
repro.obj : error LNK2019: unresolved external symbol "public: class std::slice_array<int> & __thiscall std::slice_array<int>::operator=(class std::slice_array<int> const &)" (??4?$slice_array@H@std@@QAEAAV01@ABV01@@Z) referenced in function _main
repro.exe : fatal error LNK1120: 2 unresolved externals

Expected behavior
Microsoft Visual Studio Professional 2019 Preview
Version 16.7.0 Preview 3.1

Additional context
The operators are intentionally not defined.

STL/stl/inc/valarray

Lines 941 to 943 in 3f6c715

	slice_array(const slice_array&); // not defined
	slice_array& operator=(const slice_array&); // not defined

According to cppreference, both copy constructor and assignment operator should be defined.

It confirms with [template.slice.array.overview]

This item is also tracked on Developer Community as DevCom-1075574 and by Microsoft-internal VSO-109266 / AB#109266.

The same problem is tracked on Developer Community as DevCom-246260 and by Microsoft-internal VSO-366115 / AB#366115.

The same problem with mask_array is tracked on Developer Community as DevCom-1075573.

[StephanTLavavej]

Thanks, especially for the de-duplication! I've linked the Microsoft-internal bugs to this issue.

[AlexGuteniev]

The issue is slightly more complex than I originally anticipated.
Copy constructors are trivial.
But assignments require implementation.

[AlexGuteniev]

Though if don't try to optimize, it is still easy actually, even optimal implementation is straightforward.

[AlexGuteniev]

@msalehmsft , there are three VSO links and only two AB links, was this an intention?

[StephanTLavavej]

That was me (followed by robo-@msalehmsft's hyperlink edit). The third VSO bug had already been closed as a duplicate so I didn't think it was worth linking. I just went ahead and removed that citation to avoid confusion. Thanks!