https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101135
Bug ID: 101135
Summary: Use of absent assumed-shape array argument as an
actual argument for an optional dummy argument
mistakenly flagged as error by
UndefinedBehaviourSanitizer
Product: gcc
Version: 11.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: marcel.jacobse at ewetel dot net
Target Milestone: ---
Compiling and running the minimal example
program main
implicit none
call test_wrapper
contains
subroutine test_wrapper(y)
real, dimension(1), intent(out), optional :: y
call test(y)
end subroutine test_wrapper
subroutine test(y)
real, dimension(:), intent(out), optional :: y
if (present(y)) y=0
end subroutine test
end program
with -fsanitize=undefined on any gfortran version since 8.1.0 produces this
false positive:
/app/example.f90:8:20: runtime error: load of null pointer of type
'real(kind=4)'
See for example: https://godbolt.org/z/aqGE18EGG
The issue disappears on gfortran version 7.3.0 and earlier, and also if 'y' in
'test' is not an assumed-shape array, for example if replacing 'dimension(:)'
by 'dimension(1)'. See also
https://stackoverflow.com/questions/68046152/is-passing-an-absent-assumed-shape-array-for-an-optional-argument-of-another-pro
Unfortunately I am not sure if this is an issue with gfortran itself or moreso
a false positive by UndefinedBehaviourSanitizer. So perhaps this report should
rather be for the "sanitizer" component, sorry if that is the case.
