majnemer added a comment. In D117569#3258307 <https://reviews.llvm.org/D117569#3258307>, @zahiraam wrote:
> 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? My interpretation is that MSVC has a bug: it is forming a reference to `?dll_import_int@@3HA` and not `__imp_?dll_import_int@@3HA`. Could you run a more complete experiment where you have a dll which exports the symbol and you try to import it? CHANGES SINCE LAST ACTION https://reviews.llvm.org/D117569/new/ https://reviews.llvm.org/D117569 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
