Public bug reported:
The fix for LP: #2166191 in dh-fortran 0.85ubuntu1 ("Resolve 'gfortran'
via its symlink instead of the hardcoded gfortran-16") is incomplete.
Packages that set FC_DEFAULT=gfortran still get gfortran-16, which is
not installed in stonking (the default gfortran there is 15).
Example: fortran-assert 3.1.2-1 fails to build on all architectures. The
2026-09-24 amd64 retry ran with dh-fortran 0.85ubuntu1 installed:
https://launchpad.net/ubuntu/+source/fortran-assert/3.1.2-1/+build/33466705
dh_fortran_build gfortran-16
Error: Compiler gfortran-16 not on PATH; is it installed?
FAIL: dh_fortran_build : error Command '['dh_fortran', 'get_env', '--fc',
'gfortran-16']' returned non-zero exit status 2.
The build has gfortran 4:15.2.0-5ubuntu1 and gfortran-15 installed, and
no gfortran-16. fortran-assert's debian/rules has:
export FC_DEFAULT=gfortran
== Cause ==
The 0.85ubuntu1 change fixed get_fc_flavor_arch() in
dhfortran/compilers.py, which now tries which("gfortran") and resolves
the symlink. But get_fc_default() checks the environment first and
returns before reaching that code:
def get_fc_default(fc=None) -> str:
def canon(f):
return default_compilers[f] if f in default_compilers else f
if "FC_DEFAULT" in os.environ:
return canon(os.environ["FC_DEFAULT"])
...
canon() still maps "gfortran" to the hardcoded
default_compilers["gfortran"] = "gfortran-16". So any package that sets
FC_DEFAULT=gfortran bypasses the fix.
== Suggested fix (untested) ==
Make canon() resolve the symlink first, the same way
get_fc_flavor_arch() does, and only use the table as a fallback:
def canon(f):
if f in default_compilers:
p = which(f)
if p is not None:
return Path(p).resolve().name
return default_compilers[f]
return f
Other places that use default_compilers["gfortran"] directly (e.g. the
flavor defaults around compilers.py lines 359-385, and get_f77()) may
need the same treatment.
== Note for fortran-assert ==
Fixing this alone will not make fortran-assert build. Its fpm.toml uses
"[library] type = ['shared', 'static']", which needs fpm >= 0.13.0.
Ubuntu still has fortran-fpm 0.12.0-5ubuntu1:
<ERROR>*cmd_build* Package error: Key type is not allowed in library
Debian has fortran-fpm 0.13.0-6. Ubuntu is stuck on 0.12 because of the
0.12.0-5ubuntu1 delta ("Drop build-dependencies for bootstrapping"),
which blocks auto-sync. That needs a separate merge or sync.
** Affects: dh-fortran (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2169224
Title:
dh-fortran: FC_DEFAULT=gfortran still resolves to gfortran-16
(incomplete fix for LP: #2166191)
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