So I have been reading and looking for an answer to "glibcxx_3.4.21 not found" and the glib answer seems to be "Go find a version of your program that doesn't need glibcxx_3.4.21". That seems like a cop out of an answer, is there any plan to support any newer version of glibc in CentOS 7? If the only answer to this issue is "don't use that program" then I think that I will have to dump CentOS and move to something like Fedora. I know no one at the CentOS group will care. I have already had to work around PHP5 being the last 'supported' version of PHP in CentOS despite numerous security and performance enhancements in later versions. If I am just going to keep running in to road blocks then switching is the only answer left.
TL;DR
Will there ever be a fix for glibcxx_3.4.21 not found issues?
Planned glibcxx_3.4.21Support
Re: Planned glibcxx_3.4.21Support
I'm sorry to hear of your troubles with CentOS. As for security issues, RH backports security fixes and other important changes to older versions as described in on the backporting page and CentOS inherits those fixes. The base PHP version in CentOS is unlikely to switch to a newer version, but there are newer versions available through SCL and other trustworthy repositories.
It is unlikely that CentOS would ship libraries with GLIBCXX_3.4.21 support during the lifetime of CentOS 7. If you have a program that requires 3.4.21, you may need to look at other solutions to your problem.
"Not caring" is not an accurate description. We do care, but we are restricted by what is shipped in RHEL as CentOS is a rebuild of RHEL. CentOS is not for everyone. If you are looking for a more bleeding edge solution rather than long-term stability, perhaps Fedora is a better match for you.
It is unlikely that CentOS would ship libraries with GLIBCXX_3.4.21 support during the lifetime of CentOS 7. If you have a program that requires 3.4.21, you may need to look at other solutions to your problem.
"Not caring" is not an accurate description. We do care, but we are restricted by what is shipped in RHEL as CentOS is a rebuild of RHEL. CentOS is not for everyone. If you are looking for a more bleeding edge solution rather than long-term stability, perhaps Fedora is a better match for you.
Re: Planned glibcxx_3.4.21Support
glibc is a [L]GPL package. The GPL promotes the idea that the user should have freedom to recompile program code to their platform. That means "make a version" rather than "find a version". True, all software vendors do not share the open source view. Their rationale is understandable too.
People do care. Not necessarily as vocally as RMS about GPL, but nevertheless.
SCL (Software Collections) has already rh-php71. The SCL packages by Red Hat have lifetime of about 3 years.
RHEL (and hence CentOS) has lifetime of 10 years.
Fedora has lifetime of about one year?
If you have dozens or hundreds of machines in practically 24/7 use, you certainly don't want to upgrade everything every year. Too much bleeding. Every major update requires a lot of adjustments, but your services cannot afford much downtime. A RHEL/CentOS release offers years of steady service.
In addition to SCL, there is Docker. Lighter than full VM, and allows running a program with image of Fedora/Ubuntu libs on a CentOS.