http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59781
Bug ID: 59781 Summary: Incorrect initialisation of derived type Product: gcc Version: 4.8.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: fortran Assignee: unassigned at gcc dot gnu.org Reporter: james.s.spencer at gmail dot com Created attachment 31818 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31818&action=edit Tarball containing example code, tree produced by gfortran 4.8.2 and Makefile. (Complete modules and a makefile is attached. Also confirmed against 4.6.3) With the definition type dSFMT_t private type(c_ptr) :: dSFMT_state = c_null_ptr real(c_double), allocatable :: random_store(:) end type dSFMT_t the dSFMT_t objects in the following module should both be initialised with a null pointer for the dSFMT_state component: module hilbert_space implicit none contains subroutine test_rng() use dSFMT_interface type(dSFMT_t) :: rng call dSFMT_init(7, 50000, rng) end subroutine test_rng subroutine estimate_hilbert_space() use dSFMT_interface type(dSFMT_t) :: rng call dSFMT_init(7, 50000, rng) end subroutine estimate_hilbert_space end module hilbert_space Instead only the rng object in estimate_hilbert_space is correctly initialised. The relevant parts of the tree are: estimate_hilbert_space () { struct dsfmt_t rng; try { { struct dsfmt_t dsfmt_t.0; dsfmt_t.0.dsfmt_state = 0B; dsfmt_t.0.random_store.data = 0B; rng = dsfmt_t.0; } [...] } } test_rng () { struct dsfmt_t rng; try { rng.random_store.data = 0B; [...] } } This bug is tricky to observe---small changes to the code (e.g. making rng a pointer, code reorganisation, having additional or fewer procedures in the same file, removing the random_store allocatable component etc. can lead to the dSFMT_t objects being correctly initialised. I had the above code (with additions) in a large code base for several months until an innocuous refactoring revealed it. See also discussion at https://groups.google.com/forum/#!topic/comp.lang.fortran/WogpvhUny4c, where Janus posted a smaller example which breaks under gfortran trunk.