zahiraam added a comment.
In D117569#3257121 <https://reviews.llvm.org/D117569#3257121>, @majnemer wrote:
> I have a question regarding how this work with respect to the dllimport
> semantics known by the linker.
> IIUC, we will now allow a program like:
>
> extern int __declspec(dllimport) dll_import_int;
> constexpr int& dll_import_constexpr_ref = dll_import_int;
> int& get() {
> return dll_import_constexpr_ref;
> }
>
> Here, `get` will load `dll_import_constexpr_ref`. However, what will
> `dll_import_constexpr_ref` hold? It ought to hold the contents of
> `__imp_?dll_import_int@@3HA`. However, we can't dereference
> `__imp_?dll_import_int@@3HA` to get to its contents.
@majnemer Thanks for the review.
This test case doesn't link with MSVC. It will generate this error:
Microsoft (R) Incremental Linker Version 14.29.30133.0
Copyright (C) Microsoft Corporation. All rights reserved.
/out:test1.exe
test1.obj
test1.obj : error LNK2001: unresolved external symbol "int dll_import_int"
(?dll_import_int@@3HA)
test1.exe : fatal error LNK1120: 1 unresolved externals
The symbols generated with MSVC are:
07 00000000 UNDEF notype External | ?dll_import_int@@3HA (int
dll_import_int)
015 00000000 SECT6 notype Static |
?dll_import_constexpr_ref@@3AEAHEA (int & dll_import_constexpr_ref)
Without this patch this test case errors. With this patch clang will generate
these symbols:
010 00000000 UNDEF notype External | __imp_?dll_import_int@@3HA
(__declspec(dllimport) int dll_import_int)
012 00000000 SECT5 notype External |
?dll_import_constexpr_ref@@3AEAHEA (int & dll_import_constexpr_ref)
013 00000000 UNDEF notype External | ?dll_import_int@@3HA (int
dll_import_int)
and will error at link time with this error:
test1-f1f63b.o : error LNK2019: unresolved external symbol
"__declspec(dllimport) int dll_import_int" (__imp_?dll_import_int@@3HA)
referenced in function "int & __cdecl get(void)" (?get@@YAAEAHXZ)
test1-f1f63b.o : error LNK2001: unresolved external symbol "int dll_import_int"
(?dll_import_int@@3HA)
a.exe : fatal error LNK1120: 2 unresolved externals
I think that's the behavior expected, right?
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D117569/new/
https://reviews.llvm.org/D117569
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