Re: Request to rename version.h

[Marcus Calhoun-L. <mca...@ma...>]

Greetings.

My name is Marcus Calhoun-Lopez, and Mojca was kind enough to include me in this discussion.
I originally raised this issue.

The source of the error is as follows:
*) In the file gnuplot-5.2.7/src/Makefile.in, there is the line of code
       DEFAULT_INCLUDES = -I.@am__isrc@ -I$(top_builddir)
*) The -I switch means that Clang (and GCC) search $(top_builddir) before the default include directions.
*) Clang (and GCC) have a file called version in the default included directories (likely to be part of the C++20 standard).
*) On case-insensitive file systems (like the the default macOS file system), the files version and VERSION are the same.
*) In $(top_builddir), there is a file called VERSION.
*) gnuplot indirectly has an #include <version>.
*) Instead of finding version in the default include directories, it finds the file VERSION in $(top_builddir).
*) This causes an error.

If -I$(top_builddir) is replaced with -idirafter$(top_builddir), the problem goes away.

I am sorry if this is a little long winded.
Please let me know if I can clarify.
I can create a simple test program if that would help.

Thank you,
Marcus

> On Nov 3, 2019, at 8:45 PM, Ethan Merritt (UW) <me...@uw...> wrote:
> 
> On Sunday, 03 November 2019 18:56:09 Ethan Merritt wrote:
> > > /opt/local/libexec/llvm-9.0/bin/../include/c++/v1/cstddef:37:
> > > ../version:1:1: error: expected unqualified-id
> > > 5.2
> > > ^
> > > 
> > > > And frankly, I cannot believe any tool vendor nor standardization body
> > > > would be so daft as to assume that <version.h> is a suitable name for a
> > > > new standard header.  There must be roughly several million pre-existing
> > > > user header files by that name out there that this would trample on.
> > > 
> > > Well ... the fact is that the build breaks when using the latest clang
> > > compiler. And on old OS versions this is now the default behaviour in
> > > MacPorts, so gnuplot build is currently broken for many of our users.
> >  
> > I can build from current git head using clang 9.0.0 without any problem.
> > My wxgtk version is 3.1
> >  
> > On my system cstddef.h does not refer to VERSION anywhere.
> > However that file came from gcc, not from llvm.
> > I don't know where that gets us in debugging your problem,
> > but it seems not to be a problem with clang per se.
> >  
> > Note that the syntax
> >    #include <FILENAME>
> > should only look in "a standard list of system directories".
> > I do not know where that standard list is defined, but in any
> > case it should not include the current working directory.
> > So a local file named VERSION would not conflict.
> >  
> > 	Ethan
> >  
> >  
> > > 
> > > It hardly makes sense to start pointing fingers about who was supposed
> > > to figure out that VERSION would be loaded first when one of the
> > > compiler's own files says "#include <version>" ...
> > > 
> > > Mojca
>  
> Upon further reflection...
> Your error message cannot be coming from a filename.
> It is the VERSION symbol itself that may be an issue.
> Can you compile a junk program?
>  
>     clang -o helloworld -DVERSION="6.7" helloworld.cpp
>  
> If defining VERSION breaks your compile chain that is clearly
> a problem, but it has nothing to do with gnuplot file names.
>  
> 	Ethan
>  
> -- 
> Ethan A Merritt, Dept of Biochemistry
> Biomolecular Structure Center,  K-428 Health Sciences Bldg
> MS 357742,   University of Washington, Seattle 98195-7742