External Library Detection

FoBiS can auto-detect compiler and linker flags for external libraries using pkg-config and MPI wrapper inspection — so you never have to look up -I and -L paths by hand.

pkg-config integration

List package names in the fobos [externals] section or via --pkg-config:

[externals]
pkg-config = hdf5 netcdf zlib

# Equivalent via CLI
fobis build --pkg-config hdf5 --pkg-config netcdf

FoBiS runs pkg-config --cflags --libs <name> for each package and appends the resulting flags to cflags and lflags respectively.

If a package is not found, a warning is emitted and the build continues:

Warning: external 'hdf5' could not be resolved. Flags skipped.
Check that the library is installed.

MPI auto-detection

[externals]
mpi-auto = true

fobis build --with-mpi-auto

FoBiS probes for MPI compiler wrappers in order:

1. mpifort — Fortran-specific wrapper (preferred)
2. mpif90 — legacy Fortran wrapper
3. mpif77 — Fortran 77 wrapper (last resort)

It then calls mpifort --showme:compile and --showme:link (OpenMPI) or mpifort -show (MPICH) to extract the underlying compiler flags.

The detected flags are merged with your existing cflags and lflags. This is an alternative to --mpi, which just prefixes the compiler command with mpi*.

pkg-config spec in fobos

You can also generate a .pc file for your own project so downstream consumers can link against it with pkg-config:

[pkgconfig]
name        = mylib
description = My Fortran library
version     = 1.2.0
url         = https://github.com/example/mylib
requires    = hdf5
cflags      = -I${includedir}
libs        = -L${libdir} -lmylib

# Write mylib.pc to the build directory
fobis build --write-pkgconfig

See pkg-config generation for the full option list.

Flag routing

Flags returned by pkg-config are routed automatically:

Flag pattern	Destination
-I...	cflags
-D...	cflags
-L...	lflags
-l...	lflags
-Wl,...	lflags
everything else	cflags

Combining with feature flags

External library detection and feature flags are independent and compose freely:

[features]
hdf5 = -DUSE_HDF5

[externals]
pkg-config = hdf5

When --features hdf5 is active, the -DUSE_HDF5 define is added to cflags and pkg-config hdf5 provides the include and link flags.