From 595ef8e9db0d07b4c80ee5ce27ae490011299fed Mon Sep 17 00:00:00 2001
From: Bill Somerville <bill@classdesign.com>
Date: Wed, 20 Oct 2021 18:00:32 +0100
Subject: [PATCH] Repair a long-standing defect that could cause access
 violations

This was revealed when building with gcc-fortran v11 and using
reference spectrum correction.
---
 lib/four2a.f90 | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/four2a.f90 b/lib/four2a.f90
index e7e0e8018..a63f31a4d 100644
--- a/lib/four2a.f90
+++ b/lib/four2a.f90
@@ -67,7 +67,7 @@ subroutine four2a(a,nfft,ndim,isign,iform)
 
      if(nfft.le.NSMALL) then
         jz=nfft
-        if(iform.eq.0) jz=nfft/2
+        if(iform.le.0) jz=nfft/2
         aa(1:jz)=a(1:jz)
      endif
 
@@ -87,7 +87,7 @@ subroutine four2a(a,nfft,ndim,isign,iform)
 
      if(nfft.le.NSMALL) then
         jz=nfft
-        if(iform.eq.0) jz=nfft/2
+        if(iform.le.0) jz=nfft/2
         a(1:jz)=aa(1:jz)
      endif
   end if