<div dir="ltr">Here's a simple example:<br><br> namespace x {<br> int i = 3;<br> }<br> int j = x::i;<br><br>LLVM will emit a declaration for 'i' in namespace x and a definition at the CU scope referencing the declaration. With your change, we end up omitting the DW_AT_declaration on the declaration of 'i'. The debugger then thinks it's a definition without a location, so any attempt to use/print the variable produces "this value has been optimized away".<br><br>A couple of side notes:<br><br>1) We should ideally not use "Verify()" for any debug info functionality - it should be enough to test "isBlah" methods. Any time isBlah is true but Verify fails is a bug we should fix at some point - I think that's a valid/useful invariant, but I could be wrong.<br><br>2) we don't actually need to separate declaration and definition in this way, just because the variable is inside a namespace - so if you happen to fix this by removing the separation of declaration from definition, that's OK too (& a minor win to reduce debug info size)</div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Sep 18, 2014 at 8:28 AM, Frédéric Riss <span dir="ltr"><<a href="mailto:friss@apple.com" target="_blank">friss@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><br><div><span class=""><blockquote type="cite"><div>On 18 Sep 2014, at 17:23, David Blaikie <<a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a>> wrote:</div><br><div><div dir="ltr">Looks like this might've regressed some debug scenarios:<br><br><a href="http://lab.llvm.org:8011/builders/clang-x86_64-ubuntu-gdb-75/builds/17377" target="_blank">http://lab.llvm.org:8011/builders/clang-x86_64-ubuntu-gdb-75/builds/17377</a><br><br>(could be r218040, but it seems like the less likely candidate of the two on the blame list)</div></div></blockquote><div><br></div></span><div>I’ve seen it. I sent a mail to the review thread asking for some help from someone that can run the test suite.</div><div><br></div><div>Fred</div><div><div class="h5"><br><blockquote type="cite"><div><div class="gmail_extra"><div class="gmail_quote">On Thu, Sep 18, 2014 at 2:38 AM, Frederic Riss <span dir="ltr"><<a href="mailto:friss@apple.com" target="_blank">friss@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: friss<br>
Date: Thu Sep 18 04:38:23 2014<br>
New Revision: 218041<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=218041&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=218041&view=rev</a><br>
Log:<br>
Always emit DW_AT_declaration attribute when the variable isn't a definition.<br>
<br>
Summary:<br>
This doesn't show up today as we don't emit decalration only variables. This<br>
will be tested when the followup patches implementing import of forward<br>
declared entities lands in clang.<br>
<br>
Reviewers: echristo, dblaikie, aprantl<br>
<br>
Subscribers: llvm-commits<br>
<br>
Differential Revision: <a href="http://reviews.llvm.org/D5382" target="_blank">http://reviews.llvm.org/D5382</a><br>
<br>
Modified:<br>
llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp<br>
<br>
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp?rev=218041&r1=218040&r2=218041&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp?rev=218041&r1=218040&r2=218041&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (original)<br>
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp Thu Sep 18 04:38:23 2014<br>
@@ -1670,6 +1670,9 @@ void DwarfCompileUnit::createGlobalVaria<br>
DD->addArangeLabel(SymbolCU(this, Sym));<br>
addOpAddress(*Loc, Sym);<br>
}<br>
+ // A static member's declaration is already flagged as such.<br>
+ if (!SDMDecl.Verify() && !GV.isDefinition())<br>
+ addFlag(*VariableDIE, dwarf::DW_AT_declaration);<br>
// Do not create specification DIE if context is either compile unit<br>
// or a subprogram.<br>
if (GVContext && GV.isDefinition() && !GVContext.isCompileUnit() &&<br>
@@ -1678,9 +1681,6 @@ void DwarfCompileUnit::createGlobalVaria<br>
VariableSpecDIE = &createAndAddDIE(dwarf::DW_TAG_variable, UnitDie);<br>
addDIEEntry(*VariableSpecDIE, dwarf::DW_AT_specification, *VariableDIE);<br>
addBlock(*VariableSpecDIE, dwarf::DW_AT_location, Loc);<br>
- // A static member's declaration is already flagged as such.<br>
- if (!SDMDecl.Verify())<br>
- addFlag(*VariableDIE, dwarf::DW_AT_declaration);<br>
} else {<br>
addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);<br>
}<br>
<br>
<br>
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</blockquote></div><br></div>
</div></blockquote></div></div></div><br></div></blockquote></div><br></div>