<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Mar 28, 2016 at 1:57 PM, Chaoren Lin <span dir="ltr"><<a href="mailto:chaorenl@google.com" target="_blank">chaorenl@google.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi David,<div><br></div><div>This change caused clang to produce inferior binaries that causes LLDB to go into an infinite loop while parsing their debug info.<div><br></div><div>I don't know enough about the debug information format to tell if it's clang now generating incorrect debug info due to this change, or if it's lldb incorrectly parsing the debug info (which just happen to have been working fine until now).</div><div>Could you please take a look?<br></div></div></div></blockquote><div><br></div><div>This is an "off label" use, as it were (the Split DWARF feature says that GNU_dwo_name will appear on the skeleton CU, I don't think it implies that it can't be used elsewhere - but perhaps a more careful reading than mine might imply such)<br><br>Essentially LLDB shouldn't be following GNU_dwo_name when it's already reading a CU from a dwo/dwp file already. I would consider doing this maybe one day because I have fancy ideas about how to support modules debug info using Split DWARF without needing to expand the DWARF spec* or debugger functionality - but it might need to be able to put skeleton DIEs in .dwo files & have them recursively expanded. I haven't thought about it too carefully/all the way through, so can't be sure at this point</div><div><br></div><div>* OK, maybe a little bit of extra spec wording... *shrug*<br><br>We could create a new name for the attribute if necessary - at the moment this use is just between Clang and llvm-dwp to improve diagnostics as described in the commit message.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div><div><br></div><div>For LLDB folks, it's looping through these 4 functions:</div><div><br><div>lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h:GetCompileUnitDIEPtrOnly()</div>lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h:GetCompileUnitDIEOnly()</div><div>lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp:AddCompileUnitDIE()<br></div><div>lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp:ExtractDIEsIfNeeded()<br></div><div><br></div><div><br></div></div></div></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Mar 24, 2016 at 11:37 AM, David Blaikie via llvm-commits <span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: dblaikie<br>
Date: Thu Mar 24 13:37:08 2016<br>
New Revision: 264316<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=264316&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=264316&view=rev</a><br>
Log:<br>
[debuginfo] Include dwo_name in the split unit to improve dwp diagnostics<br>
<br>
When multiple DWP files are merged together and duplicate DWO IDs are<br>
found it's currently difficult to give an actionable error message - the<br>
DW_AT_name of the CU could be provided, but might be identical (if the<br>
same source file is built into two different configurations), which<br>
doesn't help the user identify the problem.<br>
<br>
When no intermediate DWP files are generated, the path to the two DWO<br>
files could be provided - but is lost once the DWOs are merged into a<br>
DWP.<br>
<br>
So, include the name of the DWO (dwo_name) in the split file so that<br>
collissions involving a source CU from a DWP can be better diagnosed.<br>
<br>
(improvements to llvm-dwp using this to come shortly)<br>
<br>
Modified:<br>
llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp<br>
llvm/trunk/test/DebugInfo/X86/fission-cu.ll<br>
<br>
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=264316&r1=264315&r2=264316&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=264316&r1=264315&r2=264316&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)<br>
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Thu Mar 24 13:37:08 2016<br>
@@ -391,8 +391,11 @@ DwarfDebug::constructDwarfCompileUnit(co<br>
DwarfCompileUnit &NewCU = *OwnedUnit;<br>
DIE &Die = NewCU.getUnitDie();<br>
InfoHolder.addUnit(std::move(OwnedUnit));<br>
- if (useSplitDwarf())<br>
+ if (useSplitDwarf()) {<br>
NewCU.setSkeleton(constructSkeletonCU(NewCU));<br>
+ NewCU.addString(Die, dwarf::DW_AT_GNU_dwo_name,<br>
+ DIUnit->getSplitDebugFilename());<br>
+ }<br>
<br>
// LTO with assembly output shares a single line table amongst multiple CUs.<br>
// To avoid the compilation directory being ambiguous, let the line table<br>
<br>
Modified: llvm/trunk/test/DebugInfo/X86/fission-cu.ll<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/fission-cu.ll?rev=264316&r1=264315&r2=264316&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/fission-cu.ll?rev=264316&r1=264315&r2=264316&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/test/DebugInfo/X86/fission-cu.ll (original)<br>
+++ llvm/trunk/test/DebugInfo/X86/fission-cu.ll Thu Mar 24 13:37:08 2016<br>
@@ -33,6 +33,7 @@<br>
; CHECK: .debug_abbrev.dwo contents:<br>
; CHECK: Abbrev table for offset: 0x00000000<br>
; CHECK: [1] DW_TAG_compile_unit DW_CHILDREN_yes<br>
+; CHECK: DW_AT_GNU_dwo_name DW_FORM_GNU_str_index<br>
; CHECK: DW_AT_producer DW_FORM_GNU_str_index<br>
; CHECK: DW_AT_language DW_FORM_data2<br>
; CHECK: DW_AT_name DW_FORM_GNU_str_index<br>
@@ -64,38 +65,41 @@<br>
; Check that the rest of the compile units have information.<br>
; CHECK: .debug_info.dwo contents:<br>
; CHECK: DW_TAG_compile_unit<br>
-; CHECK: DW_AT_producer [DW_FORM_GNU_str_index] ( indexed (00000000) string = "clang version 3.3 (trunk 169021) (llvm/trunk 169020)")<br>
+; CHECK: DW_AT_GNU_dwo_name [DW_FORM_GNU_str_index] ( indexed (00000000) string = "baz.dwo")<br>
+; CHECK: DW_AT_producer [DW_FORM_GNU_str_index] ( indexed (00000001) string = "clang version 3.3 (trunk 169021) (llvm/trunk 169020)")<br>
; CHECK: DW_AT_language [DW_FORM_data2] (DW_LANG_C99)<br>
-; CHECK: DW_AT_name [DW_FORM_GNU_str_index] ( indexed (00000001) string = "baz.c")<br>
+; CHECK: DW_AT_name [DW_FORM_GNU_str_index] ( indexed (00000002) string = "baz.c")<br>
; CHECK-NOT: DW_AT_low_pc<br>
; CHECK-NOT: DW_AT_stmt_list<br>
; CHECK-NOT: DW_AT_comp_dir<br>
; CHECK: DW_AT_GNU_dwo_id [DW_FORM_data8] (0x1f1f859683d49324)<br>
; CHECK: DW_TAG_variable<br>
-; CHECK: DW_AT_name [DW_FORM_GNU_str_index] ( indexed (00000002) string = "a")<br>
+; CHECK: DW_AT_name [DW_FORM_GNU_str_index] ( indexed (00000003) string = "a")<br>
; CHECK: DW_AT_type [DW_FORM_ref4] (cu + 0x{{[0-9a-f]*}} => {[[TYPE:0x[0-9a-f]*]]})<br>
; CHECK: DW_AT_external [DW_FORM_flag_present] (true)<br>
; CHECK: DW_AT_decl_file [DW_FORM_data1] (0x01)<br>
; CHECK: DW_AT_decl_line [DW_FORM_data1] (1)<br>
; CHECK: DW_AT_location [DW_FORM_exprloc] (<0x2> fb 00 )<br>
; CHECK: [[TYPE]]: DW_TAG_base_type<br>
-; CHECK: DW_AT_name [DW_FORM_GNU_str_index] ( indexed (00000003) string = "int")<br>
+; CHECK: DW_AT_name [DW_FORM_GNU_str_index] ( indexed (00000004) string = "int")<br>
<br>
; CHECK: .debug_str contents:<br>
; CHECK: 0x00000000: "baz.dwo"<br>
; CHECK: 0x00000008: "/usr/local/google/home/echristo/tmp"<br>
<br>
; CHECK: .debug_str.dwo contents:<br>
-; CHECK: 0x00000000: "clang version 3.3 (trunk 169021) (llvm/trunk 169020)"<br>
-; CHECK: 0x00000035: "baz.c"<br>
-; CHECK: 0x0000003b: "a"<br>
-; CHECK: 0x0000003d: "int"<br>
+; CHECK: 0x00000000: "baz.dwo"<br>
+; CHECK: 0x00000008: "clang version 3.3 (trunk 169021) (llvm/trunk 169020)"<br>
+; CHECK: 0x0000003d: "baz.c"<br>
+; CHECK: 0x00000043: "a"<br>
+; CHECK: 0x00000045: "int"<br>
<br>
; CHECK: .debug_str_offsets.dwo contents:<br>
; CHECK: 0x00000000: 00000000<br>
-; CHECK: 0x00000004: 00000035<br>
-; CHECK: 0x00000008: 0000003b<br>
-; CHECK: 0x0000000c: 0000003d<br>
+; CHECK: 0x00000004: 00000008<br>
+; CHECK: 0x00000008: 0000003d<br>
+; CHECK: 0x0000000c: 00000043<br>
+; CHECK: 0x00000010: 00000045<br>
<br>
; Object file checks<br>
; For x86-64-linux we should have this set of relocations for the debug info section<br>
<br>
<br>
_______________________________________________<br>
llvm-commits mailing list<br>
<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a><br>
<a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits" rel="noreferrer" target="_blank">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits</a><br>
</blockquote></div><br></div>
</div></div></blockquote></div><br></div></div>