A change in the C utility routines in CHARMM was not properly propagated throughout the source, and the X11 code has failed to compile since ca. c43b1; the simple fix for this is
Code:
--- ../UMgit/charmm.lobos/source/graphics/apograph.F90	2019-08-09 14:48:45.852637000 -0400
+++ source/graphics/apograph.F90	2019-11-01 16:01:04.000000000 -0400
@@ -224,7 +224,7 @@
   implicit none
   CHARACTER(len=*) PATHNAME
 
-  INTEGER PTHLEN
+  INTEGER PTHLEN, IRET
   !
   PTHLEN=LEN(PATHNAME)
   IF(PRNLEV.GE.3) WRITE(OUTU,44) ' Invoking the command: "', &
@@ -235,7 +235,9 @@
   !     vfork() and exec()
   !     to avoid replicating all memory!
   !
-  CALL FSYSTEM(PATHNAME,PTHLEN)
+  IRET =  FSYSTEM(PATHNAME,PTHLEN)
+  IF(PRNLEV.GE.3.and.iret<0) WRITE(OUTU,45) iret
+45 format('Error: EXE returned ',I4)
   RETURN
 END SUBROUTINE GRPSHELL
 #endif /* (mainnogrhpx)*/

Delete the lines marked with a "-" prefix and add the ones marked with a "+" prefix, and the code will compile.

Rick Venable
computational chemist