[cfe-dev] Issue with checkDLLAttributeRedeclaration in SemaDecl.cpp

[Loïc Joly via cfe-dev]

Hello,

When running Clang 3.9.0 on some Windows code (I've not yet been able to reproduce the issue with a small example), we get a crash. I've been able to see that the code crashes in checkDLLAttributeRedeclaration, more specifically in the following code:

  if (OldImportAttr && !HasNewAttr && !IsInline && !IsStaticDataMember &&
      !NewDecl->isLocalExternDecl() && !IsQualifiedFriend) {
    if (IsMicrosoft && IsDefinition) {
      S.Diag(NewDecl->getLocation(),
             diag::warn_redeclaration_without_import_attribute)
          << NewDecl;
      S.Diag(OldDecl->getLocation(), diag::note_previous_declaration);
      NewDecl->dropAttr<DLLImportAttr>();
      NewDecl->addAttr(::new (S.Context) DLLExportAttr(
          NewImportAttr->getRange(), S.Context,
          NewImportAttr->getSpellingListIndex()));
    } else {

We try to read some data from NewImportAttr, but in our case, NewImportAttr is null (which is compatible with the !HasNewAttr test). I don't really understand the logic of this code, this is why I ask for advice before changing anything... Do you think I should open a bug instead of discussing on the mailing list?

It appears the code was changed in the following revision:
Revision: 270686
Author: dzobnin
Date: mercredi 25 mai 2016 13:32:42
Message:
[ms][dll] #26935 Defining a dllimport function should cause it to be exported

If we have some function with dllimport attribute and then we have the function
definition in the same module but without dllimport attribute we should add
dllexport attribute to this function definition.
The same should be done for variables.

Example:
struct __declspec(dllimport) C3 {
  ~C3();
};
C3::~C3() {;} // we should export this definition.

Patch by Andrew V. Tischenko

Differential revision: http://reviews.llvm.org/D18953



Thank you for any help,


---
Loïc



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