Long Question: What might cause the seg fault?

From	bilsch <king621@comcast.net>
Newsgroups	comp.lang.c
Subject	Long Question: What might cause the seg fault?
Date	2016-06-21 15:04 -0700
Organization	A noiseless patient Spider
Message-ID	<nkcdmc$usf$1@dont-email.me> (permalink)

Show all headers | View raw

Please see code samples #1 and #2 below.  Code sample #1 works fine. The 
output from sample #1 is shown below.

Code sample #2 below, is part of a much larger program.  I think sample 
#2 is equivalent to function fdmode() in code sample #1.  Sample #2 gets 
segmentation fault during the second iteration of function fdmode(). The 
output from sample #2 is also shown below. The seg fault occurs the 
second time fdmode() in sample #2 is called.  The seg fault happens 
after the following lines:

fdsel=quorem.rem;	
printf("fdsel = %i\n",fdsel);

QUESTION: I don't think code sample #2 contains the underlying cause of 
the seg. fault.  There is something wrong in the larger program of which 
sample #2 is a small part.  What might this be?
Note: there is no other dynamic memory allocation than that shown.
    Thanks.  Bill S.

************* output of sample #1  (works fine)   *************

fdsel = 1
w1=0.001000 w2=8.521000 w3=0.251593 nfgraf=2
fdsel = 0
w1=9.411000 w2=3.141593 w3=8.438000 nfgraf=2
fdflag = 0

****************   output of sample#2   ***********************

9.411, 1.937, 8.438, 0.001, 4, 7, 550, 325, 200, 200, 10, 6000},
7.388, 3.212, 4.428, 0.001, 3, 12, 650, 75, 350, 200, 15, 9900},
5.064, 2.101, 3.429, 0.001, 5, 1, 600, 300, 200, 125, 10, 6000},
37.500, 8.508, 0.001, 0.001, 5, 8, 600, 325, 200, 150, 20, 2400},
0.074, 6.224, 0.043, 0.010, 8, 5, 300, 300, 200, 200, 20, 2400},
0.537, 0.188, 5.493, 0.001, 6, 11, 600, 50, 200, 200, 0, 6000},
4.853, 3.434, 9.815, 0.001, 5, 1, 600, 350, 200, 200, 15, 6000},
1.861, 0.054, 0.981, 0.007, 11, 4, 400, 400, 200, 150, 0, 8000},
3.051, 7.751, 0.798, 0.001, 10, 4, 175, 400, 150, 150, 0, 8000},
0.066, 0.490, 9.919, 0.001, 10, 3, 600, 300, 200, 125, 0, 6000},
0.915, 0.573, 6.685, 0.010, 1, 7, 600, 300, 200, 200, 47, 5000},
3.300, 0.084, 0.810, 0.010, 6, 7, 650, 325, 200, 200, 6, 8000},
6.988, 0.035, 6.775, 0.001, 7, 3, 600, 300, 200, 200, 0, 8000},
6.306, 0.720, 0.058, 0.001, 9, 10, 150, 175, 150, 150, 6, 2400},
0.612, 0.517, 7.163, 0.001, 10, 6, 150, 350, 150, 150, 6, 8000},
8.130, 0.036, 0.325, 0.010, 1, 5, 600, 300, 200, 200, 0, 5000},

fdsel = 14
nfgraf=16
fdsel = 5
Segmentation fault (core dumped)

[code]
******************   code sample #1   **********************

int i=0, nfgraf=0, nx=0, n1=0, n2=0, rnum, fdflag=1, fdsel;	



float w1=0.5, w2=2.0, w3=0.14159;

float *fw1,*fw2,*fw3;

char ch;

div_t quorem;	// a structure

FILE *fp1;



int fdmode(void);



int main(int argc, char **argv){



srand(time(0));		//  current time is seed for random gen

if ((fp1 = fopen("adata", "r"))== NULL)

{	printf("error opening file named 'adata'\n");

	fclose(fp1);

	goto end;
}


i=0;

while (ch != EOF)

{       if ((ch=fgetc(fp1)) == ' ')  //  ascii 0x20 between numbers

	i++;

}

quorem=div(i,3);   // 3 numbers in each record.

nfgraf=quorem.quot;



if (quorem.rem != 0 || quorem.quot == 0)

{	printf("file named 'adata' is not evenly divisible by 3\n");

	fclose(fp1);

	goto end;
}


rewind(fp1);



while (fdflag != 0)

{

fdflag=1;
fdmode();

}

return 0;
    // end of main()
}



int fdmode(void)
{



if (nx==0)   //  nx was init. to 0

{

if ((fw1 = malloc(nfgraf * sizeof(float))) == NULL)

	printf("malloc error\n");

if ((fw2 = malloc(nfgraf * sizeof(float))) == NULL)

	printf("malloc error\n");

if ((fw3 = malloc(nfgraf * sizeof(float))) == NULL)

	printf("malloc error\n");



for (n1=0;n1<nfgraf;n1++)		//  nfgraf starts at 1

{

	fscanf(fp1,"%f %f %f",&fw1[n1],&fw2[n1],&fw3[n1]);

	printf("%2.3f, %2.3f, %2.3f\n\n",fw1[n1],fw2[n1],fw3[n1]);

}

fclose(fp1);

}	//  end of if (nx==0)	



rnum = rand();	//  this part random selects data record

quorem = div(rnum,nfgraf);

fdsel=quorem.rem;		//  fdsel is zero based

printf("fdsel = %i\n",fdsel);



w1 = fw1[fdsel];

w2 = fw2[fdsel];

w3 = fw3[fdsel];



printf("w1=%f  w2=%f   w3=%f   nfgraf=%i\n",w1,w2,w3,nfgraf);



nx++;



if (nx == nfgraf)

{

free(fw1);

free(fw2);

free(fw3);

fdflag=0;
	//  fdflag=1 when fdmode is called
printf("fdflag = 0\n");

}

return 0;

}

******************   code sample #2   **********************
int fdmode(void){

int fdsel,i;

float *fw1,*fw2,*fw3,*fk1;

int *fxf,*fyf,*fxof,*fyof,*fxm,*fym,*fdelay,*fglen;



if (nx==0)	//  nx was init. to 0

{

if ((fw1 = malloc(nfgraf * sizeof(float))) == NULL)

	printf("malloc error\n");

if ((fw2 = malloc(nfgraf * sizeof(float))) == NULL)

	printf("malloc error\n");

if ((fw3 = malloc(nfgraf * sizeof(float))) == NULL)

	printf("malloc error\n");

if ((fk1 = malloc(nfgraf * sizeof(float))) == NULL)

	printf("malloc error\n");

if ((fxf = malloc(nfgraf * sizeof(int))) == NULL)

	printf("malloc error\n");

if ((fyf = malloc(nfgraf * sizeof(int))) == NULL)

	printf("malloc error\n");

if ((fxof = malloc(nfgraf * sizeof(int))) == NULL)

	printf("malloc error\n");

if ((fyof = malloc(nfgraf * sizeof(int))) == NULL)

	printf("malloc error\n");

if ((fxm = malloc(nfgraf * sizeof(int))) == NULL)

	printf("malloc error\n");

if ((fym = malloc(nfgraf * sizeof(int))) == NULL)

	printf("malloc error\n");

if ((fdelay = malloc(nfgraf * sizeof(int))) == NULL)

	printf("malloc error\n");

if ((fglen = malloc(nfgraf * sizeof(int))) == NULL)

	printf("malloc error\n");



for (i=0;i<nfgraf;i++)		//  nfgraf starts at 1

{

	fscanf(fp1,"%f %f %f %f %i %i %i %i %i %i %i %i "

,&fw1[i],&fw2[i],&fw3[i],&fk1[i],&fxf[i],&fyf[i],&fxof[i],&fyof[i],&fxm[i],&fym[i],&fdelay[i],&fglen[i]);

	printf("%2.3f, %2.3f, %2.3f, %2.3f, %i, %i, %i, %i, %i, %i, %i, %i},\n"
 
,fw1[i],fw2[i],fw3[i],fk1[i],fxf[i],fyf[i],fxof[i],fyof[i],fxm[i],fym[i],fdelay[i],fglen[i]);

}

fclose(fp1);

}



rnum = rand();
quorem = div(rnum,nfgraf);

fdsel=quorem.rem;	//  fdsel is zero based

printf("fdsel = %i\n",fdsel);



w1 = fw1[fdsel];

w2 = fw2[fdsel];

w3 = fw3[fdsel];

k1 = fk1[fdsel];

xf = fxf[fdsel];

yf = fyf[fdsel];

xof = fxof[fdsel];

yof = fyof[fdsel];

xm = fxm[fdsel];

ym = fym[fdsel];

delay = fdelay[fdsel];

glen = fglen[fdsel];

printf("nfgraf=%i\n",nfgraf);



nx++;

if (nx == nfgraf)

{

free(fw1);

free(fw2);

free(fw3);

free(fk1);

free(fxf);

free(fyf);

free(fxof);

free(fyof);

free(fxm);

free(fym);

free(fdelay);

free(fglen);



fdflag=0;

printf("fdflag=0\n");

}

return 0;

}

[/code]

Back to comp.lang.c | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Long Question: What might cause the seg fault? bilsch <king621@comcast.net> - 2016-06-21 15:04 -0700
  Re: Long Question: What might cause the seg fault? BartC <bc@freeuk.com> - 2016-06-21 23:51 +0100
    Re: Long Question: What might cause the seg fault? BartC <bc@freeuk.com> - 2016-06-21 23:53 +0100
      Re: Long Question: What might cause the seg fault? bilsch <king621@comcast.net> - 2016-06-22 01:55 -0700
    Re: Long Question: What might cause the seg fault? John Gordon <gordon@panix.com> - 2016-06-22 00:25 +0000
  Re: Long Question: What might cause the seg fault? Jerry Stuckle <jstucklex@attglobal.net> - 2016-06-21 19:22 -0400
    Re: Long Question: What might cause the seg fault? John Gordon <gordon@panix.com> - 2016-06-22 00:17 +0000
  Re: Long Question: What might cause the seg fault? "James R. Kuyper" <jameskuyper@verizon.net> - 2016-06-21 19:35 -0400
    Re: Long Question: What might cause the seg fault? bilsch <king621@comcast.net> - 2016-06-22 03:36 -0700
  Re: Long Question: What might cause the seg fault? John Gordon <gordon@panix.com> - 2016-06-22 00:29 +0000
    Re: Long Question: What might cause the seg fault? bilsch <king621@comcast.net> - 2016-06-22 03:38 -0700
  Re: Long Question: What might cause the seg fault? Barry Schwarz <schwarzb@dqel.com> - 2016-06-21 21:20 -0700

csiph-web