<div dir="ltr">Hi Roger,<br><br>I think it was me who introduced the change from `() { }` to `() = default` for a couple of dominators-related classes during the major refactoring I did in the summer. We got reports of very similar compiler/linker failures with gcc and older versions of clang, and I thought I reverted most of them to `() {}` as a workaround. Fell free to do the same with this one.<br><br>Best regards,<br>Kuba</div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Dec 8, 2017 at 1:04 PM, David Blaikie via llvm-dev <span dir="ltr"><<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@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"><div dir="ltr">Keeping the shared library build working's probably a fine idea, though working around GCC bugs (depending on how ubiquitous they are) might be less so.<br><br>I'd be fine with this patch going in for this case, though. For a one line change there's no need to send a phab review, someone (probably me, I guess) can just apply/commit this directly.</div><div class="HOEnZb"><div class="h5"><br><div class="gmail_quote"><div dir="ltr">On Fri, Dec 8, 2017 at 1:37 AM Roger Ferrer Ibanez via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear all,<br>
<br>
while trying to build llvm with shared libraries using GCC (tested both in<br>
Ubuntu 14.04 and Ubuntu 16.04) as in<br>
<br>
cmake -G Ninja -DBUILD_SHARED_LIBS=ON<br>
<br>
I run into the following link error<br>
<br>
lib/Transforms/IPO/<wbr>CMakeFiles/LLVMipo.dir/<wbr>PartialInlining.cpp.o: In function `llvm::<wbr>ForwardDominanceFrontierBase<<wbr>llvm::BasicBlock>::<wbr>ForwardDominanceFrontierBase()<wbr>':<br>
<path>/llvm/include/llvm/<wbr>Analysis/DominanceFrontier.h:<wbr>122: undefined reference to `llvm::DominanceFrontierBase<<wbr>llvm::BasicBlock, false>::DominanceFrontierBase(<wbr>)'<br>
<br>
This change<br>
<br>
diff --git a/include/llvm/Analysis/<wbr>DominanceFrontier.h b/include/llvm/Analysis/<wbr>DominanceFrontier.h<br>
index a304dff..e743d2d 100644<br>
--- a/include/llvm/Analysis/<wbr>DominanceFrontier.h<br>
+++ b/include/llvm/Analysis/<wbr>DominanceFrontier.h<br>
@@ -52,7 +52,7 @@ protected:<br>
static constexpr bool IsPostDominators = IsPostDom;<br>
<br>
public:<br>
- DominanceFrontierBase() = default;<br>
+ DominanceFrontierBase() { }<br>
<br>
/// getRoots - Return the root blocks of the current CFG. This may include<br>
/// multiple blocks if we are computing post dominators. For forward<br>
<br>
seems to fix the problem and I think is related to this GCC defect<br>
<br>
<a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57728" rel="noreferrer" target="_blank">https://gcc.gnu.org/bugzilla/<wbr>show_bug.cgi?id=57728</a><br>
<br>
I'm unsure about the level of interest in the community when it comes to builds<br>
using shared libraries. I personally use them because for debug builds, at<br>
link time, they are less demanding in memory. However that alone might not be<br>
enough to justify this change as there are valid workarounds (like not using<br>
shared libraries, building clang with clang, using lld, etc).<br>
<br>
Thoughts? If this is reasonable I will create a Phabricator.<br>
<br>
Kind regards,<br>
Roger<br>
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</blockquote></div>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div>Jakub Kuderski</div></div>
</div>