https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123545
Bug ID: 123545
Summary: [PDT] seg fault on assigning to parent PDT
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: damian at archaeologic dot codes
Target Milestone: ---
Running the program below after compiling with the Intel ifx compiler Version
2025.2.1 Build 20250806 gives
Heading down the rabbit hole...
expecting 1.000000, read 1.000000
Running the program below after compiling with the LLVM flang compiler man
brain built 12 November 2024 (version 22.0.0git
([email protected]:llvm/llvm-project 448146d6479cdfd6b7c80cb33dbaed882dead2f1)
gives
expecting 1.000000, read 1.
both of which are acceptable results. Both runs were on macOS.
Compiling with a 20251231 build of GCC 16 give a segmentation fault. Several
comments in the program provide additional context.
$cat reproducer.F90
module julienne_fiats_m
implicit none
type string_t
character(len=:), allocatable :: string_
end type
type file_t
type(string_t), allocatable :: lines_(:)
end type
type hyperparameters_t(k) ! making this and the type below non-PDTs
eliminates the segmentation fault
integer, kind :: k = kind(1.)
real(k) :: learning_rate_ = real(1.5,k)
end type
type, extends(file_t) :: training_configuration_t(m) ! making this a non-PDT
gives a compile-time error
integer, kind :: m = kind(1.)
type(hyperparameters_t(m)) hyperparameters_
end type
contains
real function get_json_value(string)
character(len=*) string
read(string, fmt=*) get_json_value
print *,"expecting 1.000000, read ", get_json_value
end function
function hyperparameters_to_json(self) result(lines)! invoked only by
training_config_from_component
type(hyperparameters_t) self
type(string_t), allocatable :: lines(:)
integer, parameter :: max_width= 18
character(len=max_width) learning_rate_string
write(learning_rate_string,*) self%learning_rate_
lines = [string_t(learning_rate_string)]
end function
type(training_configuration_t) function
training_config_from_component(hyperparameters)
type(hyperparameters_t) hyperparameters
training_config_from_component%hyperparameters_ = hyperparameters
training_config_from_component%file_t =
file_t([hyperparameters_to_json(training_config_from_component%hyperparameters_)])
end function
function hyperparameters_from_json(lines) result(hyperparameters) ! invoked
only by training_config_from_file
type(string_t) lines(:)
type(hyperparameters_t) hyperparameters
hyperparameters%learning_rate_ = get_json_value(lines(1)%string_)
end function
type(training_configuration_t) function training_config_from_file(line)
character(len=*) line
training_config_from_file%file_t = file_t([string_t(line)]) ! segmentation
fault
training_config_from_file%hyperparameters_ =
hyperparameters_from_json(training_config_from_file%file_t%lines_)
end function
end module
use julienne_fiats_m
implicit none
type(training_configuration_t) training_configuration, from_json
training_configuration =
training_config_from_component(hyperparameters_t(learning_rate_=1.))
! Removing the above assignment eliminates the segmentation fault even though
the segmentation fault
! occurs when executing the assignment below, which does not reference the
object defined above.
! Alternatively, changing the above line to an `associate` statement gives
the compile-time
! message: "Error: Invalid kind for REAL at (1)", where the "1" is between
`use` and `fiats_m` in
! the above use statement.
print *,new_line(''), "Heading down the rabbit hole..." ! print to
demonstrate that execution continues past the above line
from_json = training_config_from_file('1.00000000')
end
$ gfortran reproducer.F90
$ ./a.out
Heading down the rabbit hole...
Program received signal SIGSEGV: Segmentation fault - invalid memory reference.
Backtrace for this error:
#0 0x7ffbde5e551f in ???
at ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
#1 0x7ffbde6483fe in __GI___libc_free
at ./malloc/malloc.c:3368
#2 0x402a69 in ???
#3 0x403ea2 in ???
#4 0x403f65 in ???
#5 0x7ffbde5ccd8f in __libc_start_call_main
at ../sysdeps/nptl/libc_start_call_main.h:58
#6 0x7ffbde5cce3f in __libc_start_main_impl
at ../csu/libc-start.c:392
#7 0x401134 in ???
#8 0xffffffffffffffff in ???
Segmentation fault (core dumped)
$ gfortran --version
GNU Fortran (GCC) 16.0.0 20251231 (experimental)
