How do you specify the item size when adding? -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Seymour J Metz Sent: Thursday, February 08, 2018 11:12 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Silly C problem adding hex 6C
Isn't pointer arithmetic in C scaled by the item size? -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List <IBM-MAIN@listserv.ua.edu> on behalf of Barkow, Eileen <ebar...@doitt.nyc.gov> Sent: Thursday, February 8, 2018 11:06 AM To: IBM-MAIN@listserv.ua.edu Subject: Silly C problem adding hex 6C I am still trying to crawl my way around C/C++ and am just trying to do one simple thing: add value 0X6C to a pointer address (which was originally supplied by this list as a means to get the jobname). something gets added to the pointer but it is not 0x6c. i tried all different combinations of char *; int *; void *; adding decimal 108; but still get the same thing. My little program correctly picks up the address of a valid ASCB (00FCAA00) from the PSA. Now I just want to point to the address at 00FCAA6C which is a pointer to the ASXB which contains the jobname at offset 0XC0. But somehow I cannot add 6C to the ASCB pointer FCAA00 and get the ASXB pointer at FCAA6C. Instead I get FCABB0 (or some other address depending on which ASCB is obtained). Can some C guru please tell me what I am doing wrong? i will post the program and results - this is running on UNIX/OMVS. MVSZ MVSZ - Storage Contents : ACSCEXB -- (00FCAA00,,SQA) ------------------- Command ===> Scroll ===> PAG Address Offset 0-1-2-3- 4-5-6-7- 8-9-A-B- C-D-E-F- 0---4---8---C--- 00FCAA00 +0 C1E2C3C2 00FBC100 00FCAB80 00000000 | ASCB..A...¿Ø.... | 00FCAA10 +10 00000000 00000000 00000000 00000000 | ................ | 00FCAA20 +20 000002E4 00780000 000100FF 00000000 | ...U.Ì.......... | 00FCAA30 +30 7FF19E00 00000000 19A77000 00000000 | "1Æ......xø..... | 00FCAA40 +40 00000000 00308F46 D3DC5674 8B346008 | ......±ãLüîÈ».-. | 00FCAA50 +50 00000000 00000000 00000000 00000000 | ................ | 00FCAA60 +60 00AFF158 FFFF8F80 00000000 00AFD000 | .®1ì..±Ø.....®}. | 00FCAA70 +70 1D171020 00000000 00000000 00AFD520 | .............®N. | 00FCAA80 +80 00000000 00000000 80AFFF98 40000000 | ........Ø®.q ... | result running jn2 $ jn2 ASCB = FCAA00 ASXB = FCABB0 $ jn2.c program #define _XOPEN_SOURCE #include <stdlib.h> #include <stdio.h> #include <string.h> #include <errno.h> #include <stdint.h> #include <iostream.h> int main(int argc, char *argv[]) { int *PSA; int *ASCB; int *ASXB; char jobname[9]; PSA=(int *)0x224; /* address of PSAAOLD */ ASCB=(int *)*PSA; printf("ASCB = %X\n",ASCB); ASXB=ASCB+0x6c; printf("ASXB = %X\n",ASXB); } to compile: c++ -+ -c -o jn2.o -I/u/eileen/j16/cons \ -I/usr/lpp/java/J8.0_64/include \ -W"c,lp64,dll,xplink,langlvl(longlong,nullptr)" jn2.c to link: c++ \ -W l,AMODE=64,lp64,LET=4,xplink,dynam=dll,case=mixed \ -I=CELQS003.x \ -o jn2 \ linkmods/CELQSTRT.o \ linkmods/CEESTART.o \ linkmods/CELQSG03.o \ linkmods/CELQINPL.o \ linkmods/CELQETBL.o \ linkmods/CELQLLST.o \ linkmods/CELQBST.o \ linkmods/CELQTRM.o \ jn2.o ________________________________ This e-mail, including any attachments, may be confidential, privileged or otherwise legally protected. It is intended only for the addressee. If you received this e-mail in error or from someone who was not authorized to send it to you, do not disseminate, copy or otherwise use this e-mail or its attachments. Please notify the sender immediately by reply e-mail and delete the e-mail from your system. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
