can't close a file??

[Michelle]

Hi,

When i compiled a program, i got a segmentation fault as follows:

Program received signal SIGSEGV, Segmentation fault.
0x42074bd0 in _int_free () from /lib/i686/libc.so.6

#0 0x42074bd0 in _int_free () from /lib/i686/libc.so.6
#1 0x42075a5c in free () from /lib/i686/libc.so.6
#2 0x4206293c in fclose@@GLIBC_2.1 () from /lib/i686/libc.so.6
#3 0x08049a76 in getNewDeploy (deploy=0x804b450) at redeploy.c:839
#4 0x08049867 in generate_table (dif=0xbfffde80) at redeploy.c:725
#5 0x08048786 in main () at redeploy.c:63
#6 0x420158f7 in __libc_start_main () from /lib/i686/libc.so.6


The error was caused by function fclose. In the program, i open a file,
read some data from it, then close it. I just checked using gdb. The
data can be read correctly. however when it comes to fclose, a seg fault
appears. Could sb. give me some ideas what may cause fclose fail? Thanks
in advance.

Best.
Michelle

 

[Mike Wahler]

Hi,

When i compiled a program, i got a segmentation fault as follows:

Program received signal SIGSEGV, Segmentation fault.
0x42074bd0 in _int_free () from /lib/i686/libc.so.6

#0 0x42074bd0 in _int_free () from /lib/i686/libc.so.6
#1 0x42075a5c in free () from /lib/i686/libc.so.6
#2 0x4206293c in fclose@@GLIBC_2.1 () from /lib/i686/libc.so.6
#3 0x08049a76 in getNewDeploy (deploy=0x804b450) at redeploy.c:839
#4 0x08049867 in generate_table (dif=0xbfffde80) at redeploy.c:725
#5 0x08048786 in main () at redeploy.c:63
#6 0x420158f7 in __libc_start_main () from /lib/i686/libc.so.6


The error was caused by function fclose.

Highly unlikely. More likely, there's something wrong
with your code.

In the program, i open a file,

Did you check the return value from 'fopen()'?

read some data from it,

Did you check your read operations for success/failure?

then close it. I just checked using gdb. The
data can be read correctly. however when it comes to fclose, a seg fault
appears. Could sb. give me some ideas what may cause fclose fail? Thanks
in advance.

You have a bug on line 47. (I.e. how the *** can we know without
seeing any code?).

-Mike

 

[Fred L. Kleinschmidt]

Hi,

When i compiled a program, i got a segmentation fault as follows:

Program received signal SIGSEGV, Segmentation fault.
0x42074bd0 in _int_free () from /lib/i686/libc.so.6

#0 0x42074bd0 in _int_free () from /lib/i686/libc.so.6
#1 0x42075a5c in free () from /lib/i686/libc.so.6
#2 0x4206293c in fclose@@GLIBC_2.1 () from /lib/i686/libc.so.6
#3 0x08049a76 in getNewDeploy (deploy=0x804b450) at redeploy.c:839
#4 0x08049867 in generate_table (dif=0xbfffde80) at redeploy.c:725
#5 0x08048786 in main () at redeploy.c:63
#6 0x420158f7 in __libc_start_main () from /lib/i686/libc.so.6

The error was caused by function fclose. In the program, i open a file,
read some data from it, then close it. I just checked using gdb. The
data can be read correctly. however when it comes to fclose, a seg fault
appears. Could sb. give me some ideas what may cause fclose fail? Thanks
in advance.

Best.
Michelle

It would help if you showed us your code.

 

[Michelle]

Hi, i attach my code here:

////////////////////////

void getNewDeploy(DeployType *deploy ) {

DeployRecType de;
AInTablePtr newptr;

int MAX_LINE_LENGTH=300;

char line[MAX_LINE_LENGTH];

char delim[] = ":";
char *tempagent, *tempstring;
char *tmpstr;

FILE *fpd;


if((fpd = fopen(DEPLOY_FILE, "r")) == NULL){
printf("\n file couldn't be found.");
exit(1);
}


int i;
for(i=0;i<MAXNODES;i++){

sprintf(de.node, "%d", i+1);
tmpstr = de.node;
newptr = NULL;

while (fgets(line, MAX_LINE_LENGTH, fpd)!= NULL){

if( strstr(line, delim) !=NULL ){
tempagent=strtok(line, delim);
tempstring=strtok(NULL,delim);

if( strstr(tempstring, tmpstr) != NULL ){
addtotable(&newptr, tempagent); ;
}
}
}

de.agents = newptr;

(*deploy)= de;

fseek(fpd,0,SEEK_SET);
}


if( fclose(fpd) != 0 )

printf( "Can't close file!" );

}

////////////////////////////////////////////////////////////


All are fine until it goes to if(fclose(fpd)!=0), where a seg fault
appears and it even doesn't print out "Can't close file!"

I guess there must be something wrong on pointers. however, i really
have no idea where the bug is...

Thanks!

michelle

 

[Mark A. Odell]

Hi, i attach my code here:

////////////////////////

void getNewDeploy(DeployType *deploy ) {

DeployRecType de;
AInTablePtr newptr;

int MAX_LINE_LENGTH=300;

char line[MAX_LINE_LENGTH];

char delim[] = ":";
char *tempagent, *tempstring;
char *tmpstr;

FILE *fpd;


if((fpd = fopen(DEPLOY_FILE, "r")) == NULL){
printf("\n file couldn't be found.");
exit(1);
}


int i;

Hey! You can't do this in C. You have defined a new variable without an
enclosing block -- syntax error unless this is really C++ in disguise.

for(i=0;i<MAXNODES;i++){

sprintf(de.node, "%d", i+1);
tmpstr = de.node;
newptr = NULL;

while (fgets(line, MAX_LINE_LENGTH, fpd)!= NULL){

if( strstr(line, delim) !=NULL ){
tempagent=strtok(line, delim);
tempstring=strtok(NULL,delim);

if( strstr(tempstring, tmpstr) != NULL ){
addtotable(&newptr, tempagent); ;
}
}
}

de.agents = newptr;

(*deploy)= de;

fseek(fpd,0,SEEK_SET);
}


if( fclose(fpd) != 0 )

printf( "Can't close file!" );

}

////////////////////////////////////////////////////////////


All are fine until it goes to if(fclose(fpd)!=0), where a seg fault
appears and it even doesn't print out "Can't close file!"

Well I can't see it. Can you load up DDD, Insight, or gdb and see what
happens to the value of 'fpd' thoughout the program? I can only guess that
the fpd pointer is getting corrupted and you are attempting to close a
non-file or some other file you aren't allowed to.

 

[Irrwahn Grausewitz]

I guess there must be something wrong on pointers. however, i really
have no idea where the bug is...

Michelle,

what looks DeployRecTyp like?
What looks AInTablePtr like?
What does addtotable() do?
Returns it a value? If so, why didn't you check it?
Why do you rewind the file every time the for loop executes?

The problem is that you did not post a compilable code sample. And if
you want to post one, cut it down to a bare minimum - most likely you
will find the error yourself when doing so (and when you are at it,
apply some consistent indentation on your code ).

This is my tip for you:
- Start commenting out chunks of code.
- Compile and test
- When the error disappears, start putting in chunks of code again.

This way you should be able to locate the error.
Using a debugger may also be helpful...

Regards

Irrwahn

 

[Irrwahn Grausewitz]

Hey! You can't do this in C. You have defined a new variable without an
enclosing block -- syntax error unless this is really C++ in disguise.

No problem, as it is enclosed in a block. It's just the bad indentation.



Irrwahn

 

[Mark A. Odell]

No problem, as it is enclosed in a block. It's just the bad indentation.

No, it isn't, in C you have to have a '{' before any variable definitions
without *any* run-time code between the '{' and the definition. E.g.

int main(void)
{
int idx; /* ok */

idx = 12;

char *pFoo; /* syntax error */

{
double fault; /* ok */

fault = 3.141592;

long boat; /* syntax error */
}

return 0;
}


Get the picture?

 

[Irrwahn Grausewitz]

No, it isn't, in C you have to have a '{' before any variable definitions
without *any* run-time code between the '{' and the definition. E.g.

int main(void)
{
int idx; /* ok */

idx = 12;

char *pFoo; /* syntax error */

{
double fault; /* ok */

fault = 3.141592;

long boat; /* syntax error */
}

return 0;
}

Get the picture?

True for C89, but AFAIK the above example is perfectly valid in C99!

Regards

Irrwahn