src/minpack.f90: ignore FPE in user-supplied subs

The minimisation algorithm may try to evaluate a function outside of its
domain triggering a floating point exception. However, this is not a
concern because it won't affect the final result, so they can be ignored

src/minpack.f90

@@ -147,7 +147,10 @@ contains
   subroutine hybrj(fcn,n,x,fvec,fjac,ldfjac,xtol,maxfev,diag,mode, &
                      factor,nprint,info,nfev,njev,r,lr,qtf,wa1,wa2, &
                      wa3,wa4)
-    use const_and_precisions, only : zero, one, epsmch=>comp_eps
+    use const_and_precisions,          only : zero, one, epsmch=>comp_eps
+    use, intrinsic :: ieee_exceptions, only : ieee_get_halting_mode, &
+                                              ieee_set_halting_mode, &
+                                              ieee_invalid
 !   arguments
     integer, intent(in) :: n, ldfjac, maxfev, mode, nprint, lr
     integer, intent(out) :: info, nfev, njev
@@ -301,7 +304,7 @@ contains
 !   local variables
     integer :: i, iflag, iter, j, jm1, l, ncfail, ncsuc, nslow1, nslow2
     integer, dimension(1) :: iwa
-    logical :: jeval, sing
+    logical :: jeval, sing, halt
     real(wp_) :: actred, delta, fnorm, fnorm1, pnorm, prered, &
             ratio, summ, temp, xnorm
 !   parameters
@@ -316,6 +319,11 @@ contains
         real(wp_), intent(inout) :: fvec(n),fjac(ldfjac,n)
       end subroutine fcn
     end interface
+
+    ! ignore NaN origiting from fcn calls
+    call ieee_get_halting_mode(ieee_invalid, halt)
+    call ieee_set_halting_mode(ieee_invalid, .false.)
+
 !  
     info = 0
     iflag = 0
@@ -582,6 +590,10 @@ contains
     if (iflag < 0) info = iflag
     iflag = 0
     if (nprint > 0) call fcn(n,x,fvec,fjac,ldfjac,iflag)
+
+    ! restore original mode
+    call ieee_set_halting_mode(ieee_invalid, halt)
+
   end subroutine hybrj
 
   subroutine hybrj1mv(fcn,n,x,f0,fvec,fjac,ldfjac,tol,info,wa,lwa)