[Plplot-general] trycompile issue with clang

[Alan W. I. <ir...@be...>]

On 2017-10-05 18:06+0200 Alaric Senat wrote:

[...]
> Today I also had another issue while attempting to specify an Osx version
> of clang to cmake, it failed to compile a test C program
> whith the osx clang version whereas I can compile mannually my own C files
> with it.
> You can find the CmakeError.log in attachment.
> It seems that the ar comand fail but I don't really get why and all the
> files in CmakeTmp are destroyed after the execution of Cmake.
> So have you an idea about where I can find this compilation test to try it
> manually to find out what's wrong ?

Hi Alaric:

I have changed the subject line to something more appropriate for this
topic.  Also, I don't mind answering occasional general cmake
questions like this one on the plplot-general mailing list for the
benefit of PLplot users, but a better place to ask such general CMake
questions is the cmake mailing list which is typically quite helpful
and which naturally brings to the attention of the CMake developers
any CMake bug you might have found.

To track down such trycompile issues like you have described I suggest
you use the latest CMake version (which is 3.9.4) (in case the
trycompile issue you have discovered is due to a CMake bug that has
been fixed in that latest version).  Also, you should use the simplest
possible CMake project which illustrates the trycompile issue, e.g., a
source directory containing just the following CMakeLists.txt file:

cmake_minimum_required(VERSION 3.9.4 FATAL_ERROR)
project(test_c_compiler C)

I haven't tried that simple project myself, but this project
should attempt a trycompile for your C compiler and that
is about all.  You should be able to
test that the above two-lines of CMake logic works in general by simply trying the gcc
compiler.  And if that test succeeds. then trying it with the clang
compiler will likely fail according to the information you have
supplied above.

Once, you have gone through all of that (gcc success + clang failure
for such a simple project), then you can debug that clang failure by
using, e.g., the cmake option --debug-trycompile. That option is only
useful for one trycompile at a time, but that is exactly what is done
in the above simple project.  Assuming this advice lets you see the
exact issue, I cannot help you further with that exact issue (I have no
experience with clang or Mac OS X), but those on the cmake mailing
list probably can help especially when you are presenting them with
such a simple test case that demonstrates the issue.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________

Linux-powered Science
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