This macro determines and display the target of an EXECUTE instruction. It is meant to be invoked with a PF key, but it can also be invoked from the command line with an address.

/*REXX --------------------------------------------------------------*/
/*                                                                   */
/* EX      - DISASM the instruction which is the target of an        */
/*           EXecute instruction and display the results in a        */
/*           message.                                                */
/*                                                                   */
/*   If the cursor is positioned on an EXecute instruction, or       */
/*   the cursor is on the command line but the address of a valid    */
/*   EXecute instruction has been entered, or if the PSW points      */
/*   to a valid EXecute instruction, dis-assemble the target of      */
/*   EXecute instruction and display the results as a message.       */
/*                                                                   */
/*-------------------------------------------------------------------*/

/*-------------------------------------------------------------------*/
/* Determine which instruction is involved.                          */
/*                                                                   */
/* If EXTRACT ARGUMENT gives RC¬=0, IDF will already have issued     */
/* an error message.  In this case, we exit with RC=-3 to prevent    */
/* IDF from overlaying that message with another that says "MACRO    */
/* RC=xx" if the argument came from the command line.                */
/*-------------------------------------------------------------------*/

 'EXTRACT ARGUMENT'
 If RC ¬= 0 Then
   Exit -3                          /* RC=-3 to prevent msg overlay  */

 If source = '' Then                /* no address provided           */
   Do
     'EXTRACT VALUE 0(PSW)'         /* use next instruction address  */
     field = Word(EXPR, 1)
   End

 address = field                    /* field level resolution        */
 'EXTRACT DISASM X'''address''''
 If RC ¬= 0 | instr = '' Then       /* not a valid instruction       */
  Do
    'SET MSG Location' address 'does not contain a valid EXecute',
                             'instruction'
    'SET ALARM'
    Exit
  End
 Parse Var instr 13 index 14 . 15 base 16 offset 19 . 35 opcode .

/*-------------------------------------------------------------------*/
/* The opcode must be EX (execute) for this macro.                   */
/*-------------------------------------------------------------------*/
 If opcode ¬= 'EX' Then
   Do
     'SET MSG' STRIP(opcode) 'is not a valid target for the EX macro'
     Exit
   End

/*-------------------------------------------------------------------*/
/* Now convert the hex index, base, and offset to an expression      */
/*-------------------------------------------------------------------*/
 reghex = '123456789ABCDEF'
 oper   = "X'"offset"'"

 If index ¬= '0' Then
   oper = oper'+0(R'index(reghex,index)')'

 If base ¬= '0' Then
   oper = oper'+0(R'index(reghex,base)')'

/*-------------------------------------------------------------------*/
/* Dump the indicated memory area and exit                           */
/*-------------------------------------------------------------------*/
 'Extract Disasm' oper
 'SET MSG' instr

 Exit