On Wed, Dec 16, 2015 at 1:15 PM, Dave Johansen <davejohansen(a)gmail.com&gt; wrote: > I'm running into a linker issue when moving code that builds on RHEL 6 to > Fedora or RHEL 7. Here's a simple reproducer: > > Download simple.c from > https://github.com/markkilgard/glut/blob/master/progs/examples/simple.c > and then run: > g++ simple.c -lglut -o simple > My SWG would be that for some reason on EL 6 you're getting the symbols for free perhaps due to the transitive nature of linking dynamic libraries? Since all you need to add is "-lGL" and it won't hurt anything on EL 6, seems like a pretty straight forward fix.

On 16/12/15 19:48, Dave Johansen wrote: > On Wed, Dec 16, 2015 at 12:32 PM, Richard Shaw <hobbes1069(a)gmail.com > <mailto:hobbes1069@gmail.com>> wrote: > > On Wed, Dec 16, 2015 at 1:15 PM, Dave Johansen > <davejohansen(a)gmail.com <mailto:davejohansen@gmail.com>> wrote: > > I'm running into a linker issue when moving code that builds on > RHEL 6 to Fedora or RHEL 7. Here's a simple reproducer: > > Download simple.c from > > https://github.com/markkilgard/glut/blob/master/progs/examples/simple.c > and then run: > g++ simple.c -lglut -o simple > > > My SWG would be that for some reason on EL 6 you're getting the > symbols for free perhaps due to the transitive nature of linking > dynamic libraries? > > Since all you need to add is "-lGL" and it won't hurt anything on EL > 6, seems like a pretty straight forward fix. > > > Yes, in this simple example the fix is easy, but in our actual code it > would mean changing the build command for hundreds of programs and > several of them depend on multiple libraries which depend on multiple > libraries, so it would be pretty time consuming. Plus, that's not even > to mention the complexity and confusion that will be added when everyone > wonders why a program is linking against a library it doesn't use. > It is using it, or you wouldn't get that error. The reference is in the .o file that the compiler has generated in /tmp for your input, not in a library you are linking to. The cause of the change in behaviour will be this: https://fedoraproject.org/wiki/UnderstandingDSOLinkChange

I think this may explain the differences you're seeing: https://fedoraproject.org/wiki/UnderstandingDSOLinkChange In short, the proper thing would be for the application in question to ilnk -lGL, you only just got away with the linker fixing it for you... until now.