https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64097
Bug ID: 64097
Summary: Bug with nested WHERE constructs
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: anlauf at gmx dot de
I encountered a problem with nested WHERE constructs, which I discussed at
https://groups.google.com/forum/#!topic/comp.lang.fortran/EG2k49ujggA
It appears that the evaluated of inner masks may not be treated (i.e. masked)
properly.
Example code:
% cat nested-where.f90
program nested_where
implicit none
integer, parameter :: n = 100
real :: x(n), y(n)
real :: z = log (0.5)
call random_number (x)
y = 1 ! "Good initialization"
y = 0 ! "Bad initialization"
print *, count (x == 1) ! Prints 0
where (x > 0.5)
y = x
where (log (y) > z) ! The "dangerous mask"
x = 1
end where
end where
print *, count (x == 1) ! Not reached for y=0
end program nested_where
The code works with NAG, PGI and xlf. It throws an FP exception when
evaluating the inner ("dangerous") mask with GCC, Intel and Crayftn,
provided FP exceptions for invalid are enabled.
Ian Harvey cited sentence 10 in section 7.2.3.2 of the standard
document, which appears to deal with this case.
