heilpern@ibd.BRL.MIL (Mark A. Heilpern ) (01/17/89)
HELPHELPHELPHELPHELPHELPHELPHELPHELPHELPHELPHELP
When running a program with the following code:
while (fscanf(input,"%d",stars)!=EOF) {
fprintf(stderr,"OK to this point.\n");
fprintf(output,"%4d |",lines++);
stars /= 50;
for (count = 0; count <= stars; count++)
fprintf(output,"*");
fprintf(output,"\n");
}
I get the following error message, NOT put out from my program:
PROTECTION VIOLATION: name='plot', pid=15943, pc=a410cdc, ps=80000180
Illegal instruction
Although this section of code indicates otherwise, I am using
standard input and output. The "OK to this point" message does
not appear when put in this position, however it does when placed
one line above. (Still giving the error message :)
The 'plot' program is not setu/gid, I've never seen a PROTECTION
VIOLATION error like this before. Any insights would be greatly
appreciated.
Mark A. Heilpern, heilpern@brl.mil
--
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/ \_(_(_)\_/ \______gwyn@smoke.BRL.MIL (Doug Gwyn ) (01/18/89)
In article <245@ibd.BRL.MIL> heilpern@brl.arpa (Mark A. Heilpern (IBD) <heilpern>) writes: > while (fscanf(input,"%d",stars)!=EOF) { > fprintf(stderr,"OK to this point.\n"); >PROTECTION VIOLATION: name='plot', pid=15943, pc=a410cdc, ps=80000180 > The "OK to this point" message does not appear when put > in this position, however it does when placed one line above. Ahem. Doesn't that TELL you something? Like perhaps there is a problem with the "while (fscanf(input,"%d",stars)!=EOF)"? In fact your problem is almost certainly that "stars" is not a pointer to an integer as required by fscanf(). Perhaps you meant "&stars".
chris@mimsy.UUCP (Chris Torek) (01/18/89)
In article <245@ibd.BRL.MIL> heilpern@ibd.BRL.MIL (Mark A. Heilpern) writes: > while (fscanf(input,"%d",stars)!=EOF) { > fprintf(stderr,"OK to this point.\n"); > fprintf(output,"%4d |",lines++); > stars /= 50; > for (count = 0; count <= stars; count++) > fprintf(output,"*"); > fprintf(output,"\n"); > } Note especially the first complaint referring to fscanf. % lint t.c t.c: t.c(6): warning: fscanf argument is type (int) rather than pointer (arg 3) fprintf returns value which is always ignored -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163) Domain: chris@mimsy.umd.edu Path: uunet!mimsy!chris
debra@alice.UUCP (Paul De Bra) (01/19/89)
In article <245@ibd.BRL.MIL> heilpern@brl.arpa (Mark A. Heilpern (IBD) <heilpern>) writes: >... > while (fscanf(input,"%d",stars)!=EOF) { >... > for (count = 0; count <= stars; count++) >... > I get the following error message, NOT put out from my program: > >PROTECTION VIOLATION: name='plot', pid=15943, pc=a410cdc, ps=80000180 >Illegal instruction From your piece of code it looks like "stars" is either an int, in which the fscanf line should have &stars, or else it is a pointer to an int, in which case the for-line should have *stars. From the protection violation i deduce it is probably the first. The error message seems strange though. I would expect a simple Illegal instruction, core dumped or Memory Fault, core dumped messge. You actually get a lot of info there. Paul. -- ------------------------------------------------------ |debra@research.att.com | uunet!research!debra | ------------------------------------------------------
jeff@tekcsc.MKT.TEK.COM (Jeff Beadles) (01/19/89)
In article <245@ibd.BRL.MIL> heilpern@brl.arpa (Mark A. Heilpern (IBD) <heilpern>) writes:
$
$ HELPHELPHELPHELPHELPHELPHELPHELPHELPHELPHELPHELP
$
$ When running a program with the following code:
$
$ while (fscanf(input,"%d", & stars)!=EOF) {
Shouldn't this be here -------^
$ fprintf(stderr,"OK to this point.\n");
$ fprintf(output,"%4d |",lines++);
$ stars /= 50;
$ for (count = 0; count <= stars; count++)
$ fprintf(output,"*");
$ fprintf(output,"\n");
$ }
$
Is it a case of the missing '&'?
-Jeff Beadles
jeff@tekcsc.MKT.TEK.COMandre@targon.UUCP (andre) (01/19/89)
In article <245@ibd.BRL.MIL> heilpern@brl.arpa (Mark A. Heilpern (IBD) <heilpern>) writes: > while (fscanf(input,"%d",stars)!=EOF) { > fprintf(stderr,"OK to this point.\n"); >PROTECTION VIOLATION: name='plot', pid=15943, pc=a410cdc, ps=80000180 I think this is a C problem namely yours. If you want scanf to fill an integer for you, you must supply a pointer to that integer and not the value of the integer so if you make your code to be: while (fscanf(input,"%d", &stars)!=EOF) { YOU FORGOT THIS _/^ the problem will go away. Hope this helps. Andre. -- ~----~ |m AAA DDDD It's not the kill, but the thrill of the chase. ~|d1|~@-- AA AAvv vvDD DD Segment registers are for worms. ~----~ & AAAAAAAvv vvDD DD ~~~~~~ -- AAA AAAvvvDDDDDD Andre van Dalen, uunet!mcvax!targon!andre
dg@lakart.UUCP (David Goodenough) (01/20/89)
From article <245@ibd.BRL.MIL>, by heilpern@ibd.BRL.MIL (Mark A. Heilpern ): > When running a program with the following code: > > while (fscanf(input,"%d",stars)!=EOF) > { > fprintf(stderr,"OK to this point.\n"); > fprintf(output,"%4d |",lines++); > stars /= 50; > for (count = 0; count <= stars; count++) > fprintf(output,"*"); > fprintf(output,"\n"); > } > > I get the following error message, NOT put out from my program: Try fscanf(input, "%d", &stars) ^ ^ TO ASSIGN INTO AN int, scanf() NEEDS THE ADDRESS As an aside, I generally avoid testing scanf() values against EOF. scanf() returns the number of successful assignments (1 in this case), so you may be a lot safer saying: while (fscanf(input, "%d", &stars) == 1) -- dg@lakart.UUCP - David Goodenough +---+ IHS | +-+-+ ....... !harvard!xait!lakart!dg +-+-+ | AKA: dg%lakart.uucp@xait.xerox.com +---+
hudson@vsedev.VSE.COM (C Hudson Hendren III) (01/20/89)
In article <245@ibd.BRL.MIL> heilpern@brl.arpa (Mark A. Heilpern (IBD) <heilpern>) writes: > > while (fscanf(input,"%d",stars)!=EOF) { ^^^^^ You need to use an ampersand before the variable name so that fscanf has the address of "stars". The line should read: while (fscanf(input,"%d",&stars)!=EOF) { > fprintf(stderr,"OK to this point.\n"); > fprintf(output,"%4d |",lines++); > stars /= 50; > for (count = 0; count <= stars; count++) > fprintf(output,"*"); > fprintf(output,"\n"); > } > > I get the following error message, NOT put out from my program: > >PROTECTION VIOLATION: name='plot', pid=15943, pc=a410cdc, ps=80000180 >Illegal instruction > > The 'plot' program is not setu/gid, I've never seen a PROTECTION > VIOLATION error like this before. Any insights would be greatly > appreciated. It would appear that PROTECTION VIOLATION on you version of unix is what most of us know to be a "segmentation violation". This error occurs when your program attempts to alter a memory location outside of it's allowed area. When you simply passed "stars" to fscanf() you were passing the actual value of stars and not the address location of "stars". The fscanf() function expects an address. If the value of "stars" happened to be zero, then fscanf() would assume that you wanted the decimal number scanned in to be stored at location zero. This is either damaged another variable or it clobbered an instruction (depending upon how your linker arranges the final binary). I guess that you clobbered an instruction since you got an illegal instruction fault. -- ==> ..!uunet!vsedev!hudson [hudson@vsedev.vse.com] (C Hudson Hendren III) <== ==> These are my opinions and are not necessarily those of VSE Corporation. <== ==> MS-DOS was created to keep idiots away from UNIX computers <==
rbj@nav.icst.nbs.gov (Nilbert T Bignum) (02/14/89)
? As an aside, I generally avoid testing scanf() values against EOF. scanf() ? returns the number of successful assignments (1 in this case), so you may ? be a lot safer saying: ... I agree. In fact, I would avoid testing the return value of scanf or fscanf against *anything*. Don't use them at all. Use fgets followed by sscanf. If you don't like the input on a particular line, it is easier to throw it away by doing another fgets than by constructing a scanf expression to read `any string terminated by newline but only up to this many characters into that junk buffer over there'. On another point, you may want to rescan the input somehow. Nilbert T Bignum <rbj@nav.icst.nbs.gov> NTSI: Never Twice the Same Institute
allbery@ncoast.ORG (Brandon S. Allbery) (02/20/89)
As quoted from <18366@adm.BRL.MIL> by rbj@nav.icst.nbs.gov (Nilbert T Bignum): +--------------- | ? As an aside, I generally avoid testing scanf() values against EOF. scanf() | ? returns the number of successful assignments (1 in this case), so you may | ? be a lot safer saying: ... | | I agree. In fact, I would avoid testing the return value of scanf or | fscanf against *anything*. Don't use them at all. Use fgets followed | by sscanf. If you don't like the input on a particular line, it is | easier to throw it away by doing another fgets than by constructing | a scanf expression to read `any string terminated by newline but only | up to this many characters into that junk buffer over there'. On another | point, you may want to rescan the input somehow. +--------------- Using scanf() for interactive input has another wart: if the (l)user doesn't enter exactly the number of data items requested, s/he won't be prompted properly for further input. And it's (almost) impossible to catch malformed data files in the non-interactive case. ++Brandon -- Brandon S. Allbery, moderator of comp.sources.misc allbery@ncoast.org uunet!hal.cwru.edu!ncoast!allbery ncoast!allbery@hal.cwru.edu Send comp.sources.misc submissions to comp-sources-misc@<backbone> NCoast Public Access UN*X - (216) 781-6201, 300/1200/2400 baud, login: makeuser