https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97920
--- Comment #5 from xin liu <xin....@compiler-dev.com> --- (In reply to Paul Thomas from comment #2) > (In reply to Martin Liška from comment #1) > > Confirmed with valgrind. At least as old as 4.9.0. > > Hi, > > From a quick perusal of the standard, I find in F2003 16.4.2.1: > > "Unless a pointer is initialized (explicitly or by default), it has an > initial association status of undefined. A pointer may be initialized to > have an > association status of disassociated". > > In your testcase, the status of b%b is undefined and so the compiler can do > anything it wants with it, including segfaulting. I think therefore that you > should initialize the derived types in your application as follows: > > type t1 > real, dimension(:), pointer :: a => NULL () > contains > final :: t1f > end type > > type, extends(t1) :: t2 > real, dimension(:), pointer :: b => NULL () > contains > final :: t2f > end type > > This clears the valgrind error "Conditional jump or move depends on > uninitialised value(s)". Also the finalization is invoked so that the > programme completes with zero memory allocation, > > To my surprise (probably due to standard ignorance), leaving the declared > type declarations as you have them, and declaring 'b' as > > type(t2) :: b = t2 (NULL(), NULL()) > > clears the valgrind fault but no finalization occurs. I notice that > finalization does not occur if an entity has the save attribute. gfortran > assigns 'b' the IMPLICIT-SAVE attribute, which is why the finalization does > not occur. I have been unable to find whether or not this is conforming. > > However, initializing 'b' in an assignment: > b = t2(NULL(), NULL()) > > clears the valgrind fault and results in the deallocation of memory. This > confirms my suspicion about the save attribute. > > In conclusion, I do not believe that this is a bug. If you do not use > pointers as pointers, make them allocatable instead. These are automatically > nullified on entry into scope. > > Thanks for the report by the way! > > Paul I get it, Thanks for your explain.
