<div dir="ltr">Hi,<br><br><div class="gmail_quote"><div dir="ltr">On Thu, Feb 18, 2016 at 3:28 PM Szilárd Páll <<a href="mailto:pall.szilard@gmail.com">pall.szilard@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<br>
Thanks for looking into this!<br>
<br>
I was not aware that zlib is only required if libxml2 was configured<br>
with it. Unless there is an easy way to check for the libxml2<br>
dependencies before the xmlTextWriterEndAttribute test is performed, I<br>
have no better suggestion. Aren't there some symbols or exported<br>
functions only present when libxml2 is configured with zlib?<br></blockquote><div><br></div><div>We could probably do that. If we adopt the tinyxml2 route, then I'd suggest we leave such libxml2 management issues as TODOs for if/when we add other code that requires functionality from libxml2.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Replacing libxml2 external dependency for this particular use-case<br>
sounds useful, although it does add some code complexity and<br>
maintenenace burden. However, I'm not sure the alternative requires<br>
less code (especially if the BG/Q issue is a very different one than<br>
what I ran into).<br></blockquote><div><br></div><div>If we don't end up needing libxml2 for anything else, then a bunch of code that we apparently don't maintain well enough currently gets to disappear, which is something.</div><div><br></div><div>Mark</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
--<br>
Szilárd<br>
<br>
<br>
On Thu, Feb 18, 2016 at 2:39 PM, Mark Abraham <<a href="mailto:mark.j.abraham@gmail.com" target="_blank">mark.j.abraham@gmail.com</a>> wrote:<br>
> Hi,<br>
><br>
> Yes, perhaps that call to check_library_exists can be improved, e.g. by<br>
> setting CMAKE_REQUIRED_LIBRARIES for the check (see<br>
> <a href="https://cmake.org/cmake/help/v3.0/module/CheckLibraryExists.html" rel="noreferrer" target="_blank">https://cmake.org/cmake/help/v3.0/module/CheckLibraryExists.html</a>). However,<br>
> it is awkward to do a good job here, because libxml2 only requires zlib if<br>
> the former was configured that way, so we have a fairly large number of<br>
> conditions to handle in constructing our handling (shared/static, whether<br>
> either was found, whether libxml2 needs zlib or not, whether test binaries<br>
> need to be built, etc.).<br>
><br>
> Roland suggested <a href="https://gerrit.gromacs.org/#/c/5630/2" rel="noreferrer" target="_blank">https://gerrit.gromacs.org/#/c/5630/2</a> but I am not sure if<br>
> it is related.<br>
><br>
> Alternatively/also, since currently the only use for XML handling in master<br>
> branch is for test reference data, I have uploaded<br>
> <a href="https://gerrit.gromacs.org/#/c/5653/" rel="noreferrer" target="_blank">https://gerrit.gromacs.org/#/c/5653/</a> to replace this use of libxml2 with a<br>
> bundled copy of tinyxml2, as part of <a href="http://redmine.gromacs.org/issues/1908" rel="noreferrer" target="_blank">http://redmine.gromacs.org/issues/1908</a><br>
> so that we get rid of such problematic external dependencies. These have<br>
> been causing grief lately for users on BG/Q machines. I suggest we keep<br>
> libxml2 detection and handling present but inactive while the future of<br>
> various patches in Gerrit gets resolved.<br>
><br>
> Mark<br>
><br>
> On Wed, Feb 10, 2016 at 4:37 PM Szilárd Páll <<a href="mailto:pall.szilard@gmail.com" target="_blank">pall.szilard@gmail.com</a>> wrote:<br>
>><br>
>> Hi,<br>
>><br>
>> $ cmake -DGMX_PREFER_STATIC_LIBS=ON -DGMX_BUILD_UNITTESTS=ON<br>
>><br>
>> [...]<br>
>> -- Looking for zlibVersion in /usr/lib/x86_64-linux-gnu/libz.a<br>
>> -- Looking for zlibVersion in /usr/lib/x86_64-linux-gnu/libz.a - found<br>
>> -- Found LibXml2: /usr/lib/x86_64-linux-gnu/libxml2.a (found version<br>
>> "2.9.1")<br>
>> -- Looking for xmlTextWriterEndAttribute in<br>
>> /usr/lib/x86_64-linux-gnu/libxml2.a<br>
>> -- Looking for xmlTextWriterEndAttribute in<br>
>> /usr/lib/x86_64-linux-gnu/libxml2.a - not found<br>
>> [...]<br>
>> CMake Error at CMakeLists.txt:562 (message):<br>
>> Cannot build unit tests without libxml2. Either set<br>
>> GMX_BUILD_UNITTESTS=OFF or tell CMake how to find a working version of<br>
>> libxml2.<br>
>><br>
>> Even though both libz and libxml are detected, the<br>
>> xmlTextWriterEndAttribute lib test fails to link as the<br>
>> check_library_exists() does not pass -lz.<br>
>><br>
>> I vaguely remember some discussion around it so I thought I'd ask<br>
>> whether this is a known issue before filing a report.<br>
>><br>
>> Are there any simple workarounds for this? (I tried passing -lz in the<br>
>> linker flags, but that does not help).<br>
>> Could we provide a better hint in the error?<br>
>><br>
>> Cheers,<br>
>> --<br>
>> Szilárd<br>
>> --<br>
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