fpm build CFLAGS

April 20, 2026

In some environments, Fortran Package Manager commands like fpm build or fpm test can fail when a dependency (say HDF5) is resolved through pkg-config and the .pc file includes a system include path such as -I/usr/include.

In that case, allow pkg-config to keep system CFLAGS via pkg-config environment variable for FPM to work:

PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 fpm build

PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1: tells pkg-config not to strip system include paths from pkg-config --cflags output.

The symptom of possibly needing this flag is:

> fpm build
<ERROR> *cmd_build* Model error: Cannot get pkg-config build flags: environment variable error.
STOP 1