The 0.85ubuntu1 fix handled get_fc_flavor_arch(), but missed
get_fc_default(). When FC_DEFAULT=gfortran is set in the environment,
canon() still returns hardcoded default_compilers["gfortran"]
("gfortran-16").
Attached debdiff dh-fortran_0.85ubuntu2 resolves the symlink in canon()
and sets default_compilers["gfortran"] from which("gfortran") at
runtime. Also added a fallback in get_f77() and a test in compilers.py.
Tested on stonking:
- pytest dhfortran/tests/compilers.py (4 passed)
- FC_DEFAULT=gfortran dh_fortran get_env --fc gfortran returns FC=gfortran-15
- debian/tests/debhelper-interaction passed
Forwarded upstream to Debian BTS:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1149705
** Description changed:
+ [ Impact ]
+ When FC_DEFAULT=gfortran is set, dh-fortran looks for gfortran-16 instead of
the installed default compiler. gfortran-16 does not exist in stonking (default
is 15), causing packages like fortran-assert to FTBFS.
+
+ The 0.85ubuntu1 fix (LP: #2166191) only touched get_fc_flavor_arch().
+ get_fc_default() checks os.environ["FC_DEFAULT"] before that and calls
+ canon(), which still returns default_compilers["gfortran"] =
+ "gfortran-16".
+
+ [ Fix ]
+ Resolve the symlink for default_compilers["gfortran"] and in canon() using
which("gfortran"). Strip architecture triplets from the target binary name so
it matches the compiler table key. Add a test in dhfortran/tests/compilers.py
for FC_DEFAULT=gfortran.
+
+ [ Test Plan ]
+ 1. Run pytest dhfortran/tests/compilers.py (all 4 tests pass).
+ 2. Run FC_DEFAULT=gfortran dh_fortran get_env --fc gfortran and check that
FC=gfortran-15 is returned.
+ 3. Run debian/tests/debhelper-interaction (exits 0).
+
+ [ Where problems could occur ]
+ If /usr/bin/gfortran points to a binary with an unexpected name format or a
broken link, it falls back to gfortran-15 (or gfortran-16).
+
+ [ Other Info ]
+ Debian bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1149705
+ Target: stonking
+
+ --- [ Original Report ]
+
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.
** Changed in: dh-fortran (Ubuntu)
Status: New => Confirmed
** Tags added: ftbfs patch stonking
** Bug watch added: Debian Bug tracker #1149705
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1149705
** Patch added: "dh-fortran 0.85ubuntu2 debdiff for stonking"
https://bugs.launchpad.net/ubuntu/+source/dh-fortran/+bug/2169224/+attachment/6004892/+files/dh-fortran_0.85ubuntu2.debdiff
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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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