# Compiltion errors on Centos 7

**URL:** <https://community.freefem.org/t/compiltion-errors-on-centos-7/872>\
**Category:** FreeFEM installation\
**Created:** [March 26, 2021, 9:53am UTC](https://community.freefem.org/t/compiltion-errors-on-centos-7/872 "2021-03-26T09:53:40Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [March 26, 2021, 10:16am UTC](https://community.freefem.org/t/compiltion-errors-on-centos-7/872/3 "2021-03-26T10:16:01Z")

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Also, I think you should be able to fix this by editing `3rdparty/ff-petsc/Makefile` and adding the flag `-D_POSIX_C_SOURCE=199309L` to `COPTFLAGS` [there](https://github.com/FreeFem/FreeFem-sources/blob/4046ffa/3rdparty/ff-petsc/Makefile#L85).  
`COPTFLAGS='-O3 $(FLAGS_MTUNE)'` → `COPTFLAGS='-D_POSIX_C_SOURCE=199309L -O3 $(FLAGS_MTUNE)'`.

Then, simply `make petsc-slepc` again.

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