问题
I need to read a file and store the data from the file into a structure. The first line of the file contains the size of the array of structs that i have to dynamically allocate.
4
12/04/2010
Interview went well I think, though was told to wear shoes.
18/04/2010
Doc advised me to concentrate on something... I forget.
03/05/2010
Was asked today if I was an art exhibit.
19/05/2010
Apparently mudcakes not made of mud, or angry wasps.
I am to run my code perfectly in Windows but when I run in Unix environment it shows me segmentation fault (core dumped). I did use valgrind to check for the memory leak and that is the results
==4344== Invalid read of size 1
==4344== at 0x407F842: ____strtol_l_internal (strtol_l.c:298)
==4344== by 0x407F606: strtol (strtol.c:108)
==4344== by 0x407C87E: atoi (atoi.c:27)
==4344== by 0x8048837: main (in /home/admininistrator/ucp/p6/gg)
==4344== Address 0x0 is not stack'd, malloc'd or (recently) free'd
==4344==
==4344==
==4344== Process terminating with default action of signal 11 (SIGSEGV)
==4344== Access not within mapped region at address 0x0
==4344== at 0x407F842: ____strtol_l_internal (strtol_l.c:298)
==4344== by 0x407F606: strtol (strtol.c:108)
==4344== by 0x407C87E: atoi (atoi.c:27)
==4344== by 0x8048837: main (in /home/admininistrator/ucp/p6/gg)
==4344== If you believe this happened as a result of a stack
==4344== overflow in your program's main thread (unlikely but
==4344== possible), you can try to increase the size of the
==4344== main thread stack using the --main-stacksize= flag.
==4344== The main thread stack size used in this run was 8388608.
==4344==
==4344== HEAP SUMMARY:
==4344== in use at exit: 1,396 bytes in 3 blocks
==4344== total heap usage: 3 allocs, 0 frees, 1,396 bytes allocated
==4344==
==4344== LEAK SUMMARY:
==4344== definitely lost: 0 bytes in 0 blocks
==4344== indirectly lost: 0 bytes in 0 blocks
==4344== possibly lost: 0 bytes in 0 blocks
==4344== still reachable: 1,396 bytes in 3 blocks
==4344== suppressed: 0 bytes in 0 blocks
==4344== Rerun with --leak-check=full to see details of leaked memory
==4344==
==4344== For counts of detected and suppressed errors, rerun with: -v
==4344== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
Segmentation fault (core dumped)
Here is my code attached
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include"struct.h"
int main(int argc, char* argv[])
{
if (argc < 2)
{
printf("You have enter less arguments.\n");
}
else if (argc > 2)
{
printf("You have enter too many arguments.");
}
else
{
FILE *file;
Diary *res;
Diary *res2;
char line[102];
int i, size, k, l, choice;
int day, month, year;
/* int d[10],m[10],y[10];*/
char as[102];
char* oken;
char* yoken;
char* coken;
oken = NULL;
yoken = NULL;
coken = NULL;
i = 0;
file = fopen("struct.txt", "r");
if (file == NULL)
{
perror("Error opening file\n.");
}
else
{
fscanf(file, "%d", &size);
res = (Diary*) malloc(size * sizeof(Diary));
res2 = (Diary*) calloc((5), sizeof(Diary));
while (fgets(line, sizeof(line), file) != NULL)
{
oken = strtok(line, "/");
if (oken != NULL)
{
res2[i].day= atoi(oken);
coken = strtok(NULL, "/");
if (oken != NULL)
{
res2[i].month = atoi(coken);
yoken = strtok(NULL, "\n ");
if (coken != NULL)
{
/*printf("%s",yoken);*/
res2[i].year = atoi(yoken);
fgets(as, 102, file);
strncpy(res2[i].entry, as, 102);
}
}
}
i++;
}
k = 1;
l = 0;
while (l < size)
{
res[l].day = res2[k].day;
res[l].month = res2[k].month;
res[l].year = res2[k].year;
strncpy(res[l].entry, res2[k].entry, 102);
k++;
l++;
}
choice = atoi(argv[1]);
printf("%d-%02d-%02d:%s",res[choice].year, res[choice].month,res[choice].day,res[choice].entry);
free(res2);
free(res);
}
fclose(file);
}
return 0;
}
I need to read all the data from the file to the struct and print it out whenever user want the entry. I tried to debug part by part, and I found out it is the part while( fgets( line, sizeof( line ), file) != NULL) that loop, gives the problem. But I have no idea how to fix it.
My struct.h is given as below:
typedef struct journal{
int day;
int month;
int year;
char entry[1024];
} Diary;
回答1:
I don't quite understand all of what you are trying to achieve, but here are a few issues.
- You probably don't need the
day month yearvariables. This line
day = atoi(oken);should probably be
res2[i].day = atoi(oken);There is a problem with the line that reads the
sizefscanf(file, "%d", &size)This reads an integer but it does not read the trailing newline
You need to change this to be something like
fscanf(file, "%d\n", &size)or use
fgets.Because of the trailing newline, the next time you call
getsyou obtain a string containing just the newline.Your
strtokcalls and NULL checks are out of phase. The first one, forokenis OK. But then you do astrtokreturningcokenbut a NULL check onokenand lastly astrtokreturningyokenand a NULL check oncoken. In all 3 cases, the call tostrtokshould be followed by a NULL check on the returned value (as is the case foroken).I don't understand the purpose of the
while (l < size)loop (maybe because of the mishandling of the newline as described above?). You allocate 5 structs, read 4 from structs.txt intores2(elements 0 to 3) then you copy elements 1 to 4 ofres2into elements 0 to 3 ofres. This means that element 0 ofres2doesn't get copied and element 4 which is all zeroes does get copied.
The cause of the crash is a combination of points 3 and 4.
I would advise against using atoi as it does no error checking. It is unsafe to use unless you are certain that the string contains a well-formed integer. If you want your code to be robust, you need to add more error checking e.g., check the return values of malloc and calloc.
来源：https://stackoverflow.com/questions/50150137/i-get-segmentation-fault-core-dumped-when-i-tried-to-run-program-with-struct