<div dir="ltr">Because StringMap's copy constructor body is:<div><br></div> assert(RHS.empty() && "Copy ctor from non-empty stringmap not implemented yet!");<div><br></div><div>:)</div></div><div class="gmail_extra">
<br><br><div class="gmail_quote">On Wed, May 7, 2014 at 4:16 PM, David Blaikie <span dir="ltr"><<a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="HOEnZb"><div class="h5">On Wed, May 7, 2014 at 3:34 PM, Lang Hames <<a href="mailto:lhames@gmail.com">lhames@gmail.com</a>> wrote:<br>
> Author: lhames<br>
> Date: Wed May  7 17:34:08 2014<br>
> New Revision: 208257<br>
><br>
> URL: <a href="http://llvm.org/viewvc/llvm-project?rev=208257&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=208257&view=rev</a><br>
> Log:<br>
> [RuntimeDyld] Make RuntimeDyldImpl::resolveExternalSymbols preserve the<br>
> relocation entries it applies.<br>
><br>
> Prior to this patch, RuntimeDyldImpl::resolveExternalSymbols discarded<br>
> relocations for external symbols once they had been applied. This causes issues<br>
> if the client calls MCJIT::finalizeLoadedModules more than once, and updates the<br>
> location of any symbols in between (e.g. by calling MCJIT::mapSectionAddress).<br>
><br>
> No test case yet: None of our in-tree memory managers support moving sections<br>
> around. I'll have to hack up a dummy memory manager before I can write a unit<br>
> test.<br>
><br>
> Fixes <rdar://problem/16764378><br>
><br>
><br>
> Modified:<br>
>     llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp<br>
><br>
> Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp<br>
> URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=208257&r1=208256&r2=208257&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=208257&r1=208256&r2=208257&view=diff</a><br>

> ==============================================================================<br>
> --- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp (original)<br>
> +++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp Wed May  7 17:34:08 2014<br>
> @@ -620,6 +620,8 @@ void RuntimeDyldImpl::resolveRelocationL<br>
>  }<br>
><br>
>  void RuntimeDyldImpl::resolveExternalSymbols() {<br>
> +  StringMap<RelocationList> ProcessedSymbols;<br>
> +<br>
>    while (!ExternalSymbolRelocations.empty()) {<br>
>      StringMap<RelocationList>::iterator i = ExternalSymbolRelocations.begin();<br>
><br>
> @@ -665,8 +667,20 @@ void RuntimeDyldImpl::resolveExternalSym<br>
>        resolveRelocationList(Relocs, Addr);<br>
>      }<br>
><br>
> +    ProcessedSymbols[i->first()] = i->second;<br>
>      ExternalSymbolRelocations.erase(i);<br>
>    }<br>
> +<br>
> +  // Restore the relocation entries that were consumed in the loop above:<br>
> +  //<br>
> +  // FIXME: Replace the following loop with:<br>
> +  //           std::swap(ProcessedSymbols, ExternalSymbolRelocations)<br>
<br>
</div></div>Presumably just: ExternalSymbolRelocations = std::move(ProcessedSymbols);<br>
<br>
swap was what you had to use for this back in C++98 when there were no<br>
move semantics.<br>
<br>
(but, yes, in either case, StringMap needs move semantic support to<br>
rewrite it that way)<br>
<div class=""><br>
> +  //        once StringMap has copy and move construction.<br>
> +  for (StringMap<RelocationList>::iterator I = ProcessedSymbols.begin(),<br>
> +                                           E = ProcessedSymbols.end();<br>
> +       I != E; ++I) {<br>
> +    ExternalSymbolRelocations[I->first()] = I->second;<br>
<br>
</div>But this code looks about as expensive as a copy anyway, so why not<br>
just write this as suggested above (Ext = std::move(Proc);) and then<br>
it'll just get 'better' if/when StringMap grows move semantics?<br>
<div class="HOEnZb"><div class="h5"><br>
> +  }<br>
>  }<br>
><br>
>  //===----------------------------------------------------------------------===//<br>
><br>
><br>
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</div></div></blockquote></div><br></div>