https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60401
--- Comment #13 from Dominik Vogt <vogt at linux dot vnet.ibm.com> --- I'm running into problems testing the latest Gcc with the latest Glibc. The test program is just #include <math.h> It's a bit difficult to provide the propert args to g++ to make it use the replacement Glibc after its own headers but before the system Glibc. This should do it: $ g++ --sysroot ~/src/git/glibc/install -std=c++11 x.C However, this results in errors with isnan and isinf: -- snip -- In file included from .../git/gcc/install/include/c++/6.0.0/math.h:36:0, from x.C:1: .../gcc/install/include/c++/6.0.0/cmath:614:11: error: ‘::isinf’ has not been declared using ::isinf; ^~~~~ .../gcc/install/include/c++/6.0.0/cmath:638:11: error: ‘::isnan’ has not been declared using ::isnan; ^~~~~ -- snip -- With -v Gcc prints this include dir search list which looks fine to me: -- snip -- ignoring nonexistent directory ".../glibc/install/usr/local/include" ignoring nonexistent directory ".../gcc/install/lib/gcc/s390x-ibm-linux-gnu/6.0.0/../../../../s390x-ibm-linux-gnu/include" #include "..." search starts here: #include <...> search starts here: .../gcc/install/lib/gcc/s390x-ibm-linux-gnu/6.0.0/../../../../include/c++/6.0.0 .../gcc/install/lib/gcc/s390x-ibm-linux-gnu/6.0.0/../../../../include/c++/6.0.0/s390x-ibm-linux-gnu .../gcc/install/lib/gcc/s390x-ibm-linux-gnu/6.0.0/../../../../include/c++/6.0.0/backward .../gcc/install/lib/gcc/s390x-ibm-linux-gnu/6.0.0/include .../gcc/install/include .../gcc/install/lib/gcc/s390x-ibm-linux-gnu/6.0.0/include-fixed .../glibc/install/usr/include End of search list. -- snip -- Not sure whether this is a Gcc issue, a Glibc issue or just bad arguments to g++.