https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126776
Bug ID: 126776
Summary: CO_MIN/CO_MAX intrinsics not implemented for character
arguments
Product: gcc
Version: 16.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libfortran
Assignee: unassigned at gcc dot gnu.org
Reporter: dobonachea at lbl dot gov
CC: damian at archaeologic dot codes
Target Milestone: ---
Created attachment 65286
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65286&action=edit
Fortran source code testing CO_MIN and CO_MAX for character arg
The CO_MIN and CO_MAX intrinsics are not implemented for character-typed
arguments.
F2023 16.9.55 and 16.9.56 specifies the A argument for CO_MAX and CO_MIN:
> Arguments
> A shall be of type integer, real, or character. ...
Demonstration:
---------------------------------------------------------
cgpu$ cat co_char3.F90
program test_co_char
implicit none
character(len=10) :: val_min, val_max
! Assign a unique character to each image
! char(65) is 'A' in ASCII.
val_min = repeat(char(65 + (num_images() - this_image())), len(val_min))
write (*,'(I2,A,A)') this_image(), ": initial val_min: ", val_min
val_max = repeat(char(65 + this_image()), len(val_min))
write (*,'(I2,A,A)') this_image(), ": initial val_max: ", val_max
! Find the minimum character across all images
call co_min(val_min)
! Find the maximum character across all images
call co_max(val_max)
sync all
! Print the results from image 1
if (this_image() == 1) then
print *, "co_min result: ", val_min
print *, "co_max result: ", val_max
end if
end program
cgpu$ gfortran --version
GNU Fortran (GCC) 16.2.0
Copyright (C) 2026 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
cgpu$ gfortran -fcoarray=lib co_char.F90 -lcaf_shmem && env
GFORTRAN_NUM_IMAGES=1 ./a.out
Fortran runtime error: min not available for type/kind combination
ERROR: Image 1(pid: 3759195) failed with signal 0, exitstatus 1.
cgpu$ gfortran -fcoarray=lib co_char.F90 -lcaf_shmem && env
GFORTRAN_NUM_IMAGES=4 ./a.out
Fortran runtime error: min not available for type/kind combination
Fortran runtime error: Fortran runtime error: Fortran runtime error: min not
available for type/kind combinationmin not available for type/kind
combinationmin not available for type/kind combination
ERROR: Image 3(pid: 3759204) failed with signal 0, exitstatus 1.
ERROR: Image 2(pid: 3759203) failed with signal 0, exitstatus 1.
ERROR: Image 1(pid: 3759202) failed with signal 0, exitstatus 1.
ERROR: Image 4(pid: 3759205) failed with signal 0, exitstatus 1.
---------------------------------------------------------
Here is the correct answer, from flang version 23.1.0-rc2:
cgpu$ flang -fcoarray co_char3.F90 -L <redacted>/lib -lcaffeine-smp-seq
-lgasnet-smp-seq && env GASNET_PSHM_NODES=4 a.out
warning: Support for multi image Fortran features is still experimental and in
development.
2: initial val_min: CCCCCCCCCC
3: initial val_min: BBBBBBBBBB
2: initial val_max: CCCCCCCCCC
3: initial val_max: DDDDDDDDDD
1: initial val_min: DDDDDDDDDD
1: initial val_max: BBBBBBBBBB
4: initial val_min: AAAAAAAAAA
4: initial val_max: EEEEEEEEEE
co_min result: AAAAAAAAAA
co_max result: EEEEEEEEEE
And from NAG 7.2:
headroom$ nagfor -coarray co_char3.F90 && env NAGFORTRAN_NUM_IMAGES=4 a.out
NAG Fortran Compiler Release 7.2(Shin-Urayasu) Build 7238
[NAG Fortran Compiler normal termination]
1: initial val_min: DDDDDDDDDD
1: initial val_max: BBBBBBBBBB
3: initial val_min: BBBBBBBBBB
3: initial val_max: DDDDDDDDDD
4: initial val_min: AAAAAAAAAA
4: initial val_max: EEEEEEEEEE
2: initial val_min: CCCCCCCCCC
2: initial val_max: CCCCCCCCCC
co_min result: AAAAAAAAAA
co_max result: EEEEEEEEEE
