<div dir="ltr">How would you enforce that, other than to ask people to try to remember not to do it? It seems to me like std::atomic not being copy-constructible is telling you that, well, you shouldn't be copying it.<div><br></div><div>BTW, nobody has commented on my original concern that the atomic may not even be necessary in the first place.</div></div><br><div class="gmail_quote"><div dir="ltr">On Fri, Aug 26, 2016 at 5:13 PM Greg Clayton <<a href="mailto:gclayton@apple.com">gclayton@apple.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">There is no need to delete the lldb_private::Address copy constructor. Just stop functions from passing it by value.<br>
<br>
> On Aug 26, 2016, at 1:13 PM, Zachary Turner <<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>> wrote:<br>
><br>
> IOW, marking it =delete() is no different than deleting the copy constructor above, but at least if you mark it delete, maybe someone will read the comment above it that explains why it's deleted :)<br>
><br>
> On Fri, Aug 26, 2016 at 1:13 PM Zachary Turner <<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>> wrote:<br>
> I think so. But in this case lldb::Address explicitly supplied a copy constructor that looked like this:<br>
><br>
> Address (const Address& rhs) :<br>
> m_section_wp (rhs.m_section_wp),<br>
> m_offset(rhs.m_offset.load()) // this is the std::atomic<><br>
> {<br>
> }<br>
><br>
> circumventing the problem.<br>
><br>
> On Fri, Aug 26, 2016 at 1:11 PM Mehdi Amini <<a href="mailto:mehdi.amini@apple.com" target="_blank">mehdi.amini@apple.com</a>> wrote:<br>
>> On Aug 26, 2016, at 1:02 PM, Zachary Turner via lldb-dev <<a href="mailto:lldb-dev@lists.llvm.org" target="_blank">lldb-dev@lists.llvm.org</a>> wrote:<br>
>><br>
>> It seems to be. I will also make the copy constructor =delete() to make sure this cannot happen again.<br>
><br>
> Just curious: if a member has a deleted copy-ctor (like std::atomic right?), isn’t the copy constructor automatically deleted?<br>
><br>
> —<br>
> Mehdi<br>
><br>
><br>
>><br>
>> I'm still concerned that the std::atomic is unnecessary, but at that point at least it just becomes a performance problem and not a bug.<br>
>><br>
>> On Fri, Aug 26, 2016 at 1:00 PM Greg Clayton <<a href="mailto:gclayton@apple.com" target="_blank">gclayton@apple.com</a>> wrote:<br>
>> So after speaking with local experts on the subject, we do indeed have a problem. Please convert all placed where we pass lldb_private::Address by value to pass by "const Address &". Anyone that is modifying the address should make a local copy and work with that.<br>
>><br>
>> Is Address the only class that is causing problems?<br>
>><br>
>> Greg<br>
>><br>
>> > On Aug 26, 2016, at 10:51 AM, Zachary Turner via lldb-dev <<a href="mailto:lldb-dev@lists.llvm.org" target="_blank">lldb-dev@lists.llvm.org</a>> wrote:<br>
>> ><br>
>> > I recently updated to Visual Studio 2015 Update 3, which has improved its diagnostics. As a result of this, LLDB is uncompilable due to a slew of errors of the following nature:<br>
>> ><br>
>> > D:\src\llvm\tools\lldb\include\lldb/Target/Process.h(3256): error C2719: 'default_stop_addr': formal parameter with requested alignment of 8 won't be aligned<br>
>> ><br>
>> > The issue comes down to the fact that lldb::Address contains a std::atomic<uint64_t>, and is being passed by value pervasively throughout the codebase. There is no way to guarantee that this value is 8 byte aligned. This has always been a bug, but until now the compiler just hasn't been reporting it.<br>
>> ><br>
>> > Someone correct me if I'm wrong, but I believe this is a problem on any 32-bit platform, and MSVC is just the only one erroring.<br>
>> ><br>
>> > I'm not really sure what to do about this. Passing std::atomic<uint64>'s by value seems wrong to me.<br>
>> ><br>
>> > Looking at the code, I don't even know why it needs to be atomic. It's not even being used safely. We'll have a single function write the value and later read the value, even though it could have been used in the meantime. Maybe what is really intended is a mutex. Or maybe it doesn't need to be atomic in the first place.<br>
>> ><br>
>> > Does anyone have a suggestion on what to do about this? I'm currently blocked on this as I can't compile LLDB.<br>
>> > _______________________________________________<br>
>> > lldb-dev mailing list<br>
>> > <a href="mailto:lldb-dev@lists.llvm.org" target="_blank">lldb-dev@lists.llvm.org</a><br>
>> > <a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev" rel="noreferrer" target="_blank">http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev</a><br>
>><br>
>> _______________________________________________<br>
>> lldb-dev mailing list<br>
>> <a href="mailto:lldb-dev@lists.llvm.org" target="_blank">lldb-dev@lists.llvm.org</a><br>
>> <a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev" rel="noreferrer" target="_blank">http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev</a><br>
<br>
</blockquote></div>