getting heap corruption detected when freeing memory with calloc and changed stdout [duplicate]

Question

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How should character arrays be used as strings? (4 answers)

Closed 10 months ago.

I am trying to change the stdout into a file, write something and than retrun it back to screen. My code is :

FILE *stream ;
char * file_name = "LRA_SOLVER";
char * file_ext = ".txt";
char file_number [3] = {0};
itoa (lra_solver_couter++,file_number,10);
char* file_full_name = (char*)calloc(strlen(file_number)+10+4,sizeof(char));
strcpy(file_full_name, file_name);
strcat(file_full_name, file_number);
strcat(file_full_name, file_ext); 
if((stream = freopen(file_full_name, "w", stdout)) == NULL)
    exit(-1);
print(); // a lot of printing into the file.
stream = freopen("CON", "w", stdout); // change it back
free(file_full_name);

but I am getting the error heap corruption detected... the lra_solver_couter isn't big (usually 0-20). What am I doing wrong ?

Answer 1

You forgot the terminating '\0' when you calculate the needed length of file_full_name: You only have strlen(file_number)+10+4 with 10 == strlen(file_name) and 4 == strlen(file_ext). Add 1 for `\0'.