http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52673
Bug #: 52673
Summary: implement -fheap-arrays in gfortran
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: fortran
AssignedTo: [email protected]
ReportedBy: [email protected]
Consider p1
subroutine ss3(ia)
integer :: ia(*)
ia(6)=1 ! out-of-bound access
end subroutine ss3
subroutine ss2(ia)
integer :: ia(*)
call ss3(ia)
end subroutine ss2
subroutine ss1
integer :: ia(3) ! local array
call ss2(ia)
end subroutine ss1
program p1
call ss1
end program p1
and p2
subroutine ss3(ia)
integer :: ia(*)
ia(6)=1 ! out-of-bound access
end subroutine ss3
subroutine ss2(ia)
integer :: ia(*)
call ss3(ia)
end subroutine ss2
subroutine ss1
integer, allocatable :: ia(:) ! local allocatable array
allocate( ia(3) )
call ss2(ia)
end subroutine ss1
program p2
call ss1
end program p2
Both p1 and p2 contain an array out-of-bound access. However, valgrind will
only detect the illegal in p2 as the local array on p1 is allocated on the
stack.
Compiling with "-fstack-protector-all" may occasionally help but not in this
case.
A useful option would be "-fheap-arrays" which would allocate all local arrays
on the heap to make it easier to detect memory corruption using tool such as
valgrind. All local arrays of constant size or unknown size ("automatic
arrays") should be dealt with.
This is essentially the opposite of "-fstack-arrays": make the program slower
to detect memory problems.
An possible small optimisation could be to keep the arrays not passed to other
routines on the stack as local bound run-time checking (-fcheck=bounds) should
be sufficient to detect problems.
Note that the Intel Fortran compiler offers "-heap-arrays" to allocate
automatic arrays on the heap. This does not do anything to local arrays of size
known at compile time.
