Checked for existing upstream reports, and reduced the ICE to a minimal
reproducer.
Minimal reproducer (gfortran-15 15.3.0-4ubuntu1 and gfortran-16
16.2.0-3ubuntu1 on stonking amd64):
$ cat m.f90
module m
interface
module function g() result(n)
integer :: n
end function
end interface
abstract interface
function f() result(n)
integer :: n
end function
end interface
procedure(f), pointer :: p
end module m
$ cat s.f90
submodule(m) s
contains
module procedure g
n = 0
if (associated(p)) n = 1
end procedure
end submodule s
$ gfortran -c m.f90 && gfortran -c -flto s.f90
s.f90:6:15: internal compiler error: in write_symbol, at
lto-streamer-out.cc:3086 (GCC 16: line 3096)
* Trigger: referencing a module-level procedure pointer variable (here just
associated(p); calling p() also triggers it) from within a submodule, compiled
with -flto (any -O level).
* The same reference from a separate module that USEs m works, and so does the
submodule if it doesn't reference p, or without -flto.
* In fortran-julienne this is julienne_multi_image_s.F90, built with
-DJULIENNE_PARALLEL_CALLBACKS=1 (the julienne_this_image/... procedure
pointers).
Existing upstream reports: GCC's bugzilla isn't reachable from here (bot
protection), so I searched the [email protected] archive. Nothing matches
this case:
* PR126170 (July 2026, fixed on master as r17-2332, "Fix LTO ICE in
copy_function_or_variable"): another gfortran LTO ICE, caused by a duplicated
derived-type vtab symbol from a redundant USE; different symbol and trigger.
Its regression PR126210 is about that fix.
* PR82586 / PR71861 ("ICE in write_symbol(): bad module symbol"): these are
module-file write_symbol in gcc/fortran/module.cc, not lto-streamer-out.cc.
* PR93158 / PR93424 / PR99798 (submodule ICEs): different paths, no LTO.
So, as far as can be checked from here, this looks unreported. Someone
with bugzilla access should search for "write_symbol lto-streamer-out"
and then file a new PR (component fortran or lto) with the reproducer
above, mentioning GCC 15.3.0 and 16.2.0.
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https://bugs.launchpad.net/bugs/2169866
Title:
fortran-julienne 4.1.0-1 FTBFS: gfortran ICE in write_symbol (lto-
streamer-out.cc:3086) with LTO
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