I build gcc from source sometime yesterday. Everything seem OK during the build process and I install it in my /home/xxx/opt/ without root. But when I try to use it to compile my function, an error was told like: 'aligned_alloc' was not defined in this scope After some search on the Internet I find it is a new feature in C++11 and may be in 'stdlib.h'. I'm quite sure I included this in my cpp file. and of course get the -std=c++14 option when build my code. Curiously I searched my /home/xxx/opt directory and find few 'stdlib.h' file but all not contain useful code, there are just some usings. I think it's not right. So I am confused that if there are some operations I missed for this or I just didnt use it in appropriate way. and how I get an 'stdlib.h' that contains 'aligned_alloc'. my info: centOS 6 (no root privillage) previous GCC : 4.4.7 target GCC : 5.3.0/5.5.0 (I tried both and get same situation) I installed gmp mpfr mpc all from source in the same directory above. and no error reported LD_LIBRARY_PATH and some other path are set too. It seems my new GCC can be use in some place. I tried to build a python3 from source and get a success.