<div dir="ltr"><div>I confirm GCC4.8 puts <span style="font-size:12.8px">derived0<int, int, 1024u> into DWARF and LLDB correctly identifies dynamic type.</span></div><div> </div></div><div class="gmail_extra"><br><div class="gmail_quote">2017-02-06 11:48 GMT-08:00 Robinson, Paul via lldb-dev <span dir="ltr"><<a href="mailto:lldb-dev@lists.llvm.org" target="_blank">lldb-dev@lists.llvm.org</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">So is LLDB expecting the name in the DWARF info to match the demangled name of the vtable pointer? The DWARF spec does not really specify what the name of
a template instantiation should be, and in particular does not *want* to specify whether it matches any given demangler's opinion of the name.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">--paulr<u></u><u></u></span></p>
<p class="MsoNormal"><a name="m_-2336013961287235621__MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></a></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> lldb-dev [mailto:<a href="mailto:lldb-dev-bounces@lists.llvm.org" target="_blank">lldb-dev-bounces@<wbr>lists.llvm.org</a>]
<b>On Behalf Of </b>Greg Clayton via lldb-dev<br>
<b>Sent:</b> Monday, February 06, 2017 11:08 AM<br>
<b>To:</b> Greg Clayton<br>
<b>Cc:</b> <a href="mailto:lldb-dev@lists.llvm.org" target="_blank">lldb-dev@lists.llvm.org</a><br>
<b>Subject:</b> Re: [lldb-dev] RTTI does not work stable in LLDB.<u></u><u></u></span></p>
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<p class="MsoNormal">So I found the problem. This is a compiler bug. The DWARF for this type looks like:<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">0x000065da: TAG_structure_type [112] *<br>
AT_containing_type( {0x0000000000006628} )<br>
AT_name( "derived0<int, int, 1024>" )<br>
AT_byte_size( 0x08 )<br>
AT_decl_file( "/private/tmp/<wbr>main.cpp" )<br>
AT_decl_line( 9 )<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">But all of the type info in the symbol table has has the type named as "derived0<int, int, 1024u>”. Note the extra “u” that follows 1024. This stops LLDB from being able to lookup the type correctly so we can show the dynamic type. In LLDB
we check the first pointer inside of a class to see if it is a symbol whose name is “<span style="font-size:8.5pt;color:#d12f1b">vtable for TYPENAME”. If it is, we lookup the type “TYPENAME” to find it. In this case we try to lookup </span>"derived0<int, int,
1024u>” and we fail since the DWARF has it as "derived0<int, int, 1024>”.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">I have filed a radar on the compiler here at Apple for the fix.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Greg<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<u></u><u></u></p>
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<p class="MsoNormal">On Feb 6, 2017, at 10:22 AM, Greg Clayton via lldb-dev <<a href="mailto:lldb-dev@lists.llvm.org" target="_blank">lldb-dev@lists.llvm.org</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">I am looking at this now. I will let you know what I find.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Greg<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">On Feb 6, 2017, at 10:00 AM, Roman Popov <<a href="mailto:ripopov@gmail.com" target="_blank">ripopov@gmail.com</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Yes, that was my thought. <u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">FYI, checked in GDB: it's working correctly on this testcase showing correct dynamic type in both cases.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">2017-02-06 9:48 GMT-08:00 Greg Clayton <<a href="mailto:gclayton@apple.com" target="_blank">gclayton@apple.com</a>>:<u></u><u></u></p>
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<p class="MsoNormal">You have found a bug. It should be reporting this correctly but it isn’t. I verified it fails on MacOSX.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Greg Clayton<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">On Feb 5, 2017, at 1:19 PM, Roman Popov via lldb-dev <<a href="mailto:lldb-dev@lists.llvm.org" target="_blank">lldb-dev@lists.llvm.org</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Hello,<u></u><u></u></p>
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<p class="MsoNormal">I'm observing very strange LLDB behavior: it does not always shows a correct dynamic type when I ask for.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Originally I was working with LLDB 3.9, but it looks like trunk version behaves the same strange way. <u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">I was able to capture this behavior in a small code snippet: <u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">#include <iostream></span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">#include <typeinfo></span><u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">using namespace std;</span><u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">struct base_type { virtual ~base_type(){} };</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">template <class T1, class T2, unsigned SIZE></span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">struct derived0 : base_type {};</span><u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">template <class T1, class T2></span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">struct derived1 : base_type {};</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">int main(int argc, char ** argv) {</span><u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> base_type * bptr0 = new derived0<int, int, 1024>();</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> base_type * bptr1 = new derived1<int, int >();</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> cout << typeid(*bptr0).name() << endl;</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> cout << typeid(*bptr1).name() << endl;</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> return 0;</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">}</span><u></u><u></u></p>
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<p class="MsoNormal">lldb --version<u></u><u></u></p>
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<p class="MsoNormal">lldb version 5.0.0 (<a href="http://llvm.org/svn/llvm-project/lldb/trunk" target="_blank">http://llvm.org/svn/llvm-<wbr>project/lldb/trunk</a> revision 293398)<u></u><u></u></p>
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<p class="MsoNormal"> clang revision 293398<u></u><u></u></p>
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<p class="MsoNormal"> llvm revision 293398<u></u><u></u></p>
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<p class="MsoNormal">Testing in LLDB:<u></u><u></u></p>
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<p class="MsoNormal">(lldb) break set --file main.cpp --line 22<u></u><u></u></p>
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<p class="MsoNormal">(lldb) expression -d no-run -- bptr1<u></u><u></u></p>
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<p class="MsoNormal">(derived1<int, int> *) $2 = 0x0000000000614c40<u></u><u></u></p>
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<p class="MsoNormal">(lldb) expression -d no-run -- bptr0<u></u><u></u></p>
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<p class="MsoNormal"><b>(base_type *) $3 = 0x0000000000614c20</b><u></u><u></u></p>
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<p class="MsoNormal">Can someone explain me why for bptr0 I dont get a <span style="font-family:"Courier New"">derived0<int, int, 1024> * as I expected?</span><u></u><u></u></p>
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<p class="MsoNormal">Thanks,<u></u><u></u></p>
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<p class="MsoNormal">Roman<u></u><u></u></p>
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<p class="MsoNormal">______________________________<wbr>_________________<br>
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