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Thank you. That would appear to contradict C++11 14.7.1 paragraph 8 which said "The implicit instantiation of a class template does not cause any static data members of that class to be implicitly instantiated." This paragraph seems to have expanded into
C++17 17.8.1 paragraph 10, but still includes static data members.</div>
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Could you explain how this example does not violate that language?<br>
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-Troy<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> David Blaikie <dblaikie@gmail.com><br>
<b>Sent:</b> Monday, September 23, 2019 11:23 AM<br>
<b>To:</b> Troy Johnson <troyj@cray.com><br>
<b>Cc:</b> cfe-dev@lists.llvm.org <cfe-dev@lists.llvm.org><br>
<b>Subject:</b> Re: [cfe-dev] unnecessary implicit instantiation?</font>
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<div dir="ltr">I believe the rules are that since 'M' is not dependent on any template parameters, it can be checked without deferring until the point of instantiation. (& that it isn't /required/ to be checked - it's up to the compiler, so both GCC and Clang
are correct here)</div>
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<div dir="ltr" class="x_gmail_attr">On Mon, Sep 23, 2019 at 8:07 AM Troy Johnson via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org">cfe-dev@lists.llvm.org</a>> wrote:<br>
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If there's a different email list for C++ language questions like this, please let me know, since I'm trying establish which compiler's behavior is correct before I try to change anything in Clang. The standard is a little fuzzy on this matter because it says
that the instantiation occurs as needed, and one could argue that one does not need to know the size of a static data member in order to use the class type as part of another definition. Clang seems to want the whole definition of the class, including static
data, to be fully defined before using it.<br>
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-Troy<br>
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<div id="x_gmail-m_-5586942480484149259divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> cfe-dev <<a href="mailto:cfe-dev-bounces@lists.llvm.org" target="_blank">cfe-dev-bounces@lists.llvm.org</a>>
on behalf of Troy Johnson via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>><br>
<b>Sent:</b> Wednesday, September 18, 2019 4:26 PM<br>
<b>To:</b> <a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a> <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>><br>
<b>Subject:</b> [cfe-dev] unnecessary implicit instantiation?</font>
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Clang issues an error for the following code, whereas the GNU compiler does not. Based on the standard, I think that an implicit instantiation should not occur because the compiler is not yet allocating an object, and that would mean that Clang is incorrectly
issuing an error and GNU is correct to not issue any error.<br>
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Is my understanding correct?<br>
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<span>> cat t.cpp<br>
</span>
<div>template <typename T> class A;<br>
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<div><br>
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<div>template <typename T><br>
</div>
<div>struct B {<br>
</div>
<div> static A<int> M;<br>
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<div>};<br>
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<div><br>
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<div>template <typename T> A<int> B<T>::M;<br>
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<div>> g++ -c t.cpp<br>
</div>
<div>> clang -c t.cpp<br>
</div>
t.cpp:8:36: error: implicit instantiation of undefined template 'A<int>'<br>
<div>template <typename T> A<int> B<T>::M;<br>
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<div> ^<br>
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<div>t.cpp:1:29: note: template is declared here<br>
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<div>template <typename T> class A;<br>
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<div> ^<br>
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<span>1 warning and 1 error generated.</span></div>
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Thanks,</div>
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Troy<br>
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