
<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">In ELF files if there is a section named “<font color="#d12f1b" class=""><span style="font-size: 11px;" class="">.gnu_debuglink” it will contain a path to the external debug file. Dump this section and see what it contains. </span></font><span style="font-size: 11px; color: rgb(209, 47, 27);" class="">This section contains a null terminated C string as the path followed by a 4 byte aligned 32 bit integer which is a file CRC. </span><span style="color: rgb(209, 47, 27); font-size: 11px;" class="">Check to see the path is relative.</span><div class=""><font color="#d12f1b" class=""><span style="font-size: 11px;" class=""><br class=""></span></font></div><div class=""><font color="#d12f1b" class=""><span style="font-size: 11px;" class="">I am guessing this is your problem.</span></font></div><div class=""><font color="#d12f1b" class=""><span style="font-size: 11px;" class=""><br class=""></span></font></div><div class=""><font color="#d12f1b" class=""><span style="font-size: 11px;" class="">Greg</span></font></div><div class=""><font color="#d12f1b" class=""><span style="font-size: 11px;" class=""><br class=""></span></font><div class=""><font color="#d12f1b" class=""><span style="font-size: 11px;" class=""><br class=""></span></font><div><blockquote type="cite" class=""><div class="">On Jan 9, 2017, at 3:42 PM, Jeffrey Tan <<a href="mailto:jeffrey.fudan@gmail.com" class="">jeffrey.fudan@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Hey Greg, I just confirmed this with our build team. I seem to have misunderstood the location of debug symbol. It is actually not inside each individual object file but:<div class=""><div style="margin: 0px; padding: 0px; font-family: 'san francisco', -apple-system, blinkmacsystemfont, '.sfnstext-regular', sans-serif; color: rgb(29, 33, 41); font-size: 12px; letter-spacing: -0.24px; background-color: rgb(246, 247, 249);" class="">The debug info in <code style="background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial;background-color:rgb(233,235,238);font-size:10.8px;padding:1px 4px;font-family:menlo,consolas,monaco,monospace;letter-spacing:normal" class="">dev</code> mode sits in the <code style="background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial;background-color:rgb(233,235,238);font-size:10.8px;padding:1px 4px;font-family:menlo,consolas,monaco,monospace;letter-spacing:normal" class="">.debug_*</code> sections of the shared libraries<span class="gmail-text_exposed_show" style="display:inline;font-family:inherit"> (we don't use debug fission).</span></div><div class="gmail-text_exposed_show" style="display:inline;font-family:"san francisco",-apple-system,blinkmacsystemfont,".sfnstext-regular",sans-serif;color:rgb(29,33,41);font-size:12px;letter-spacing:-0.24px;background-color:rgb(246,247,249)"><div style="margin: 0px; padding: 0px; font-family: inherit;" class="">One potential complicating factor is that we relativize the <code style="background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial;background-color:rgb(233,235,238);font-size:10.8px;padding:1px 4px;font-family:menlo,consolas,monaco,monospace;letter-spacing:normal" class="">DW_AT_comp_dir</code>attributes in the DWARF info, so that it's almost always just a long reference to the current working directory (e.g. <code style="background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial;background-color:rgb(233,235,238);font-size:10.8px;padding:1px 4px;font-family:menlo,consolas,monaco,monospace;letter-spacing:normal" class="">.///</code>).</div><div style="margin: 0px; padding: 0px; font-family: inherit;" class=""><br class=""></div><div style="margin: 0px; padding: 0px; font-family: inherit;" class="">I do not know why this(symbol in shared library) would cause the bug though.</div><div style="margin: 0px; padding: 0px; font-family: inherit;" class=""><br class=""></div><div style="margin: 0px; padding: 0px; font-family: inherit;" class="">Jeffrey</div></div></div></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Mon, Jan 9, 2017 at 1:57 PM, Greg Clayton <span dir="ltr" class=""><<a href="mailto:clayborg@gmail.com" target="_blank" class="">clayborg@gmail.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class="">Comments below.<div class=""><br class=""><div class=""><span class=""><blockquote type="cite" class=""><div class="">On Jan 9, 2017, at 1:10 PM, Jeffrey Tan via lldb-dev <<a href="mailto:lldb-dev@lists.llvm.org" target="_blank" class="">lldb-dev@lists.llvm.org</a>> wrote:</div><br class="m_6798138216981228047Apple-interchange-newline"><div class=""><div dir="ltr" class="">Hi,<div class=""><br class=""></div><div class="">O ur company is using Buck(<a href="https://buckbuild.com/" target="_blank" class="">https://buckbuild.com/</a>) to build internal service. Recently the build team made a change in buck to not merge dwarf symbols from each object file into final binary so debugger needs to read source/symbol table from compilation unit itself.</div></div></div></blockquote><div class=""><br class=""></div></span>How are debug symbols expected to be found? Is fission being used where the DWARF for each compile unit is in .dwo files and the main executable has skeleton DWARF? I will skip all other questions until we know more about how and where the DWARF is.</div></div><span class="HOEnZb"><font color="#888888" class=""><div class=""><br class=""></div><div class="">Greg Clayton</div><div class=""><br class=""></div></font></span></div></blockquote></div><br class=""></div>

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