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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Hi David,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">OK, I got that DIE in Compile Unit scope may point to a DIE in subprogram scope.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">But how about that we are emitting a subprogram entry that has no attributes?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal">0x0000002b: DW_TAG_subprogram [3] *<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">0x0000002c: DW_TAG_typedef [4]<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_type [DW_FORM_ref4] (cu + 0x0040 => {0x00000040})<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_name [DW_FORM_strp] ( .debug_str[0x00000060] = "T")<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_decl_file [DW_FORM_data1] ("c:\temp\ICL\LB\retain.cpp")<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_decl_line [DW_FORM_data1] (16)<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></a></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Amjad<o:p></o:p></span></p>
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<p class="MsoNormal"><a name="_____replyseparator"></a><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> David Blaikie [mailto:dblaikie@gmail.com]
<br>
<b>Sent:</b> Saturday, April 30, 2016 17:59<br>
<b>To:</b> Aboud, Amjad <amjad.aboud@intel.com><br>
<b>Cc:</b> Adrian Prantl <aprantl@apple.com>; llvm-dev <llvm-dev@lists.llvm.org>; Clang Dev <cfe-dev@lists.llvm.org><br>
<b>Subject:</b> Re: Debug info scope of explicit casting type does not seem correct<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Yep, seems fine/reasonable to me. The pointer type has no logical scope so it doesn't really matter where its DIE goes.<br>
<br>
GCC does put the pointer type in the function scope in basic cases, but it can also end up in other places. For example:<o:p></o:p></p>
<pre><span style="color:black">blaikie@blaikie-linux:~/dev$ cat func.cpp<o:p></o:p></span></pre>
<pre><span style="color:black">void sink(void*);<o:p></o:p></span></pre>
<pre><span style="color:black">template<typename T><o:p></o:p></span></pre>
<pre><span style="color:black">void f1() {<o:p></o:p></span></pre>
<pre><span style="color:black"> T *t;<o:p></o:p></span></pre>
<pre><span style="color:black"> sink(&t);<o:p></o:p></span></pre>
<pre><span style="color:black">}<o:p></o:p></span></pre>
<pre><span style="color:black">void f2() {<o:p></o:p></span></pre>
<pre><span style="color:black"> struct foo { };<o:p></o:p></span></pre>
<pre><span style="color:black"> f1<foo>();<o:p></o:p></span></pre>
<pre><span style="color:black">}<o:p></o:p></span></pre>
<pre><span style="color:black">blaikie@blaikie-linux:~/dev$ g++-4.7 -std=c++11 func.cpp -g -c && llvm-dwarfdump-tot -debug-dump=info func.o | grep DW_TAG<o:p></o:p></span></pre>
<pre><span style="color:black">0x0000000b: DW_TAG_compile_unit [1] *<o:p></o:p></span></pre>
<pre><span style="color:black">0x0000002d: DW_TAG_subprogram [2] * // f2<o:p></o:p></span></pre>
<pre><span style="color:black">0x00000051: DW_TAG_lexical_block [3] <o:p></o:p></span></pre>
<pre><span style="color:black">0x00000062: DW_TAG_structure_type [4] <o:p></o:p></span></pre>
<pre><span style="color:black">0x0000006b: DW_TAG_subprogram [5] * // f1<o:p></o:p></span></pre>
<pre><span style="color:black">0x00000087: DW_TAG_template_type_parameter [6] <o:p></o:p></span></pre>
<pre><span style="color:black">0x0000008e: DW_TAG_lexical_block [7] *<o:p></o:p></span></pre>
<pre><span style="color:black">0x0000009f: DW_TAG_variable [8] <o:p></o:p></span></pre>
<pre><span style="color:black">0x000000ab: DW_TAG_pointer_type [9] // foo*<o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">& in fact, if you introduce another template that's similar to f1, its variable's type is 0x00ab - so it points into f1's children. Seems GCC puts it in whatever scope first references the pointer type.<o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">I think it's probably as sensible, and a bit simpler, to put any such basic types in the CU scope.<o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">(granted, if GCC and Clang were really smart, the pointer type in f1 could be pointer to 0x0087 - but that would really bloat the debug info (now every different way of writing foo* in every different template would be a separate type description... - that would probably be not good))<o:p></o:p></span></pre>
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<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">On Sat, Apr 30, 2016 at 3:32 AM, Aboud, Amjad <<a href="mailto:amjad.aboud@intel.com" target="_blank">amjad.aboud@intel.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hi,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I am wondering if this behavior of creating debug info is correct.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">A type in compile unit entry is pointing to a type under subprogram entry?!<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">This is the root cause of
<a href="https://llvm.org/bugs/show_bug.cgi?id=27579" target="_blank">https://llvm.org/bugs/show_bug.cgi?id=27579</a><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">0x0000000b: DW_TAG_compile_unit [1] *<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">0x00000026: DW_TAG_pointer_type [2]<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> DW_AT_type [DW_FORM_ref4] (cu + 0x002c => {<span style="background:yellow">0x0000002c</span>})<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">0x0000002b: DW_TAG_subprogram [3] *<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="background:yellow">0x0000002c</span>: DW_TAG_typedef [4]<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> DW_AT_type [DW_FORM_ref4] (cu + 0x0040 => {0x00000040})<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> DW_AT_name [DW_FORM_strp] ( .debug_str[0x00000060] = "T")<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> DW_AT_decl_file [DW_FORM_data1] ("c:\temp\ICL\LB\retain.cpp")<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> DW_AT_decl_line [DW_FORM_data1] (16)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">0x00000037: NULL<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">command line:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">clang -cc1 -triple i386-apple-ios9.0.0 -emit-obj -debug-info-kind=limited -O2 test.cpp –o - | llvm-dwarfdump -debug-dump=info -<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">> cat test.cpp<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">class A {<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">public:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> int x;<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">};<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">class B {<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">public:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> typedef A type;<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">};<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">template<typename X><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">int foo(void* in) {<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> typedef typename X::type T;<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> const T* p = (T*) in;<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> return p->x;
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">}<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">int bar() {<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">A a;<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> return foo<B>(&a);<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">}<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Reason for this behavior is the explicit cast “(T*)“, which leads into the following IR:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.9.0 (trunk 267335)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug,
enums: !2, retainedTypes: <span style="background:yellow">!3</span>)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="background:yellow">!3</span> = !{<span style="background:yellow">!4</span>}<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="background:yellow">!4</span> = !DIDerivedType(tag: DW_TAG_pointer_type, baseType:
<span style="background:yellow">!5</span>, size: 32, align: 32) <----------------- No Scope, leads to compile unit scope!!<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="background:yellow">!5</span> = !DIDerivedType(tag: DW_TAG_typedef, name: "T", scope:
<span style="background:yellow">!7</span>, file: !6, line: 16, baseType: !20)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="background:yellow">!7</span> = distinct !<span style="background:yellow">DISubprogram</span>(name: "foo<B>", linkageName: "_Z3fooI1BEiPv", scope: !6, file: !6, line:
15, type: !8, isLocal: false, isDefinition: true, scopeLine: 15, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !12, variables: !15)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thanks,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Amjad<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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