Always emit DW_AT_declaration attribute when the variable isn't a definition.

[friss]

Summary

This doesn't show up today as we don't emit decalration only variables. This
will be tested when the followup patches implementing import of forward
declared entities lands in clang.

[echristo]

This sounds like we'd want DIEs for global variable declarations or have I missed something?

[friss]

It's not that we want declarations for all globals, but sometimes a declaration is all we have:

namespace ns {
extern int A;
}
using ns::A;
int foo(int Arg = A) { return Arg; }

In the above, if we want to emit the imported_declaration or the default argument, we want to have a declaration only DIE for the global.

[echristo]

Ah right. OK with the testing coming in short order via the rest of it as we get patches :)

[friss]

Closed by commit rL218041 (authored by @friss).

[friss]

This commit seems to have broken the gdb test suite:

http://lab.llvm.org:8011/builders/clang-x86_64-ubuntu-gdb-75/builds/17377/steps/gdb-75-check/logs/stdio http://lab.llvm.org:8011/builders/clang-x86_64-ubuntu-gdb-75/builds/17377/steps/gdb-75-check/logs/stdio

If someone with access to gdb test suite could help me figure it out, that would be great.

Fred

[echristo]

You can check out the testcases yourself from svn and take a look at the
differences in the 3 failing tests as far as debug info. They're short.

-eric

lib/CodeGen/AsmPrinter/DwarfUnit.cpp

if (GV.getGlobal()->isThreadLocal()) {
                 DD->getAddressPool().getIndex(Sym, /* TLS */ true));
       }
       // 3) followed by a custom OP to make the debugger do a TLS lookup.
       addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_GNU_push_tls_address);
     } else {
       DD->addArangeLabel(SymbolCU(this, Sym));
       addOpAddress(*Loc, Sym);
     }
+    // A static member's declaration is already flagged as such.
+    if (!SDMDecl.Verify() && !GV.isDefinition())
+      addFlag(*VariableDIE, dwarf::DW_AT_declaration);
     // Do not create specification DIE if context is either compile unit
     // or a subprogram.
     if (GVContext && GV.isDefinition() && !GVContext.isCompileUnit() &&
         !GVContext.isFile() && !DD->isSubprogramContext(GVContext)) {
       // Create specification DIE.
       VariableSpecDIE = &createAndAddDIE(dwarf::DW_TAG_variable, UnitDie);
       addDIEEntry(*VariableSpecDIE, dwarf::DW_AT_specification, *VariableDIE);
       addBlock(*VariableSpecDIE, dwarf::DW_AT_location, Loc);
-      // A static member's declaration is already flagged as such.
-      if (!SDMDecl.Verify())
-        addFlag(*VariableDIE, dwarf::DW_AT_declaration);
     } else {
       addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
     }
     // Add the linkage name.
     StringRef LinkageName = GV.getLinkageName();
     if (!LinkageName.empty())
       // From DWARF4: DIEs to which DW_AT_linkage_name may apply include:
       // TAG_common_block, TAG_constant, TAG_entry_point, TAG_subprogram and