<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Mar 22, 2016 at 3:59 PM, Pete Cooper 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: pete<br>
Date: Tue Mar 22 17:59:35 2016<br>
New Revision: 264115<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=264115&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=264115&view=rev</a><br>
Log:<br>
Avoid memcpy from nullptr.  NFC.<br>
<br>
This was caught by the UBSan bot.  When the atom has no size, we would<br>
issue a memcpy with size0 and a nullptr for the source.<br>
<br>
Also, this code should never have references inside an empty atom so<br>
add an assert for that while we're here.<br>
<br>
Modified:<br>
    lld/trunk/lib/ReaderWriter/MachO/ArchHandler_x86.cpp<br>
<br>
Modified: lld/trunk/lib/ReaderWriter/MachO/ArchHandler_x86.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/MachO/ArchHandler_x86.cpp?rev=264115&r1=264114&r2=264115&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/MachO/ArchHandler_x86.cpp?rev=264115&r1=264114&r2=264115&view=diff</a><br>
==============================================================================<br>
--- lld/trunk/lib/ReaderWriter/MachO/ArchHandler_x86.cpp (original)<br>
+++ lld/trunk/lib/ReaderWriter/MachO/ArchHandler_x86.cpp Tue Mar 22 17:59:35 2016<br>
@@ -420,6 +420,11 @@ void ArchHandler_x86::generateAtomConten<br>
                                           FindAddressForAtom findSectionAddress,<br>
                                           uint64_t imageBaseAddress,<br>
                                           uint8_t *atomContentBuffer) {<br>
+  if (!atom.size()) {<br>
+    assert(atom.begin() == atom.end() &&<br>
+           "Cannot have references without content");<br></blockquote><div><br></div><div>Um, that seems like a problematic API, if size can be distinct from end() - begin() ? Perhaps some of these should be renamed to avoid confusion?</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
+    return;<br>
+  }<br>
   // Copy raw bytes.<br>
   memcpy(atomContentBuffer, atom.rawContent().data(), atom.size());<br>
   // Apply fix-ups.<br>
<br>
<br>
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</blockquote></div><br></div></div>