CODEWITHSUNDEEP
cvisual-c++file-io
Granger Obliviate
Granger Obliviate

Reputation: 151

Error reading variable from a file Microsoft Visual C

So I am executing a code that reads values from a file and process them. The workable code is below, and I can provide the file too.

FILE *fp1, *fp2;
short input_filt=0, output_filt=-32767; 
unsigned short alpha = 23528, i=0;

fp1=fopen("sine1kHz.mat", "r");
if(fp1==NULL)
    return 0;
fp2=fopen("filter.mat", "w"); 

for (i=0; i<1024; i++)
{
    fscanf(fp1, "%d", &input_filt);
    output_filt=(output_filt*alpha)+(input_filt*(1-alpha)); 
    fprintf(fp2, "%d %d\n", input_filt, output_filt);
}

fclose(fp1);
fclose(fp2);

return 0;

So I debugged and the reading from the file is absolutely fine. So there are no problems while I am in the loop (no access to values non existent). However, once I leave the loop the program crashes and Microsoft Visual Studio gives me this message:

"Run-Time Check Failure #2 - Stack around the variable 'input_filt' was corrupted."

Any idea why this is happening and how to fix it? Thank you!

Upvotes: 0

Views: 31

Answers (1)

dbush
dbush

Reputation: 223689

You're using the wrong format specifier for scanf.

The %d format specifier to scanf expects an int * argument, however you're passing in a short *. Since a short is smaller than an int on your system, scanf will write past the memory used by input_filt when the value is read in.

You want to use %hd instead which tells it to expect a short *.

fscanf(fp1, "%hd", &input_filt);

Note that it isn't strictly necessary to use %hd for printf because a short value passed to a variadic function will be automatically promoted to int.

Upvotes: 2

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