[cmake-developers] [PATCH] New module FindLibDl

[Roger Leigh]

On Tue, Nov 25, 2014 at 11:41:46AM -0500, Brad King wrote:
> On 11/21/2014 02:59 PM, Chuck Atkins wrote:
> > dlopen defined in dlfcn.h is part of POSIX so generally if you're
> > on a *nix system then you can rely on it being there.  The associated
> > library, however, is a different story, hence CMAKE_DL_LIBS.
> 
> My initial reaction to Roger's post was to say that CMAKE_DL_LIBS was
> created very early in CMake and I think a module like FindLibDl would
> supersede it.  However, Chuck raises a valid point.  The dlfcn.h header
> may be in a toolchain-defined path so "finding" it ourselves may get
> the wrong one.  We don't have find modules for "unistd.h" for example.
> 
> Perhaps it is simplest to update the documentation of CMAKE_DL_LIBS
> to explain this.

I don't have a problem with using CMAKE_DL_LIBS, but I am reluctant to
use it unconditionally.  While it's true that most current unix systems
support it, looking at POSIX.1-2001 it's in XSI as an optional interface
so isn't strictly guaranteed to be present.  It would be really nice to
have an an accompanying variable e.g. CMAKE_DL_FOUND which confirms that
it's safe to use, since I can't infer this from an empty CMAKE_DL_LIBS
when it's part of the standard library.

It would be equally nice to know if common-but-nonstandard extensions
such as dladdr(3) were safe to use.


Regards,
Roger

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