https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68993
Bug ID: 68993
Summary: MERGE does not evaluate its arguments
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: Joost.VandeVondele at mat dot ethz.ch
Target Milestone: ---
I'm not 100% sure what the right answer is, i.e. if MERGE is defined by the
standard to do something special with respect to evaluating its arguments. The
origin is code like this:
MERGE(C_NULL_PTR, C_LOC(pc), .NOT.PRESENT(pc)))
is this standard conforming if pc is not present ? In that case MERGE is
supposed to return C_NULL_PTR, but I see no reason why C_LOC(pc) would not be
evaluated first.
Gfortran and ifort behave differently in this respect.In the below code ifort
calls foo 4x while gfortran calls it 2x.
While gfortran's way of doing things seem natural, I suspect it is not standard
conforming.
> cat test.f90
MODULE test
INTEGER, SAVE :: i=0
CONTAINS
INTEGER FUNCTION foo()
i=i+1
foo=i
END FUNCTION
END MODULE test
USE test
WRITE(6,*) MERGE(foo(),foo(),.FALSE.)
WRITE(6,*) MERGE(foo(),foo(),.FALSE.)
WRITE(6,*) i
END
> gfortran test.f90 && ./a.out
1
2
2
> ifort test.f90 && ./a.out
2
4
4
