Overlapping and too long integer values in dynamic c structs - c

Question

I have the following problem.
I need to create a list of savestates with dynamical length. That's why I decided to create a list by defining some structs and connecting dynamically created structs together to build a list of structs which can dynamically be extended and so on.
However, some things seem to not work at all. Here's the relevant code first:
saves.h:
#ifndef SAVES_H
#include<time.h>
#define SAVES_H
#define SVS_STRLEN 500
#define SVS_FILE "savefile.dat"
#define True 1
#define False 0
typedef struct SVS_STATE SVS_STATE;
typedef struct SVS_STATES SVS_STATES;
struct SVS_STATE {
int i_playfield[6][7];
int i_turn;
time_t i_time;
void *next;
};
struct SVS_STATES {
SVS_STATE *states;
int count;
int loaded;
};
void SVS_Add_State(int i_playfield[][7], int i_turn, time_t i_time);
void SVS_Debug_State(SVS_STATE *state);
void SVS_Format_State(SVS_STATE *state, char text[]);
SVS_STATE *SVS_Get_State(int number);
#endif
saves.c:
#include "saves.h"
#include<string.h>
#include<time.h>
SVS_STATE *SVS_Get_State(int number)
{
int i = 1;
SVS_STATE *state;
if (svs_current_state.loaded == False) return NULL;
if (number > svs_current_state.count) return NULL;
state = svs_current_state.states;
printf("printing state 1:");
SVS_Debug_State(state);
while( i < number)
{
i++;
state = (SVS_STATE*)(state->next);
printf("printing state %i:", i);
SVS_Debug_State(state);
}
return state;
}
void SVS_Format_State(SVS_STATE *state, char text[])
{
int i, j;
if (svs_current_state.loaded == False) return;
text[0] = '\0';
strcat(text, "{\0");
for (i = 0; i < X_SIZE; i++)
{
strcat(text, "{\0");
for(j = 0; j < Y_SIZE; j++)
{
strcat(text, "%i,\0");
sprintf(text, text, state->i_playfield[i][j]);
}
strcat(text, "}\0");
}
strcat(text, "};%i;%i\n\0");
sprintf(text, text, state->i_turn, state->i_time);
printf("\nFormatted state:%s\n", text);
}
void SVS_Debug_State(SVS_STATE *state)
{
char text[SVS_STRLEN];
SVS_Format_State(state, text);
printf("%s\n", text);
}
void SVS_Add_State(int i_playfield[][7], int i_turn, time_t i_time)
{
int i, j;
SVS_STATE *laststate, *newstate;
newstate = (SVS_STATE*)malloc(sizeof(SVS_STATE));
printf("adding state with time:%i\n", i_time);
if (svs_current_state.loaded == False) return;
for (i = 0; i < 6; i++)
for (j = 0; j < 7; j++)
newstate->i_playfield[i][j] = i_playfield[i][j];
newstate->i_turn = i_turn;
newstate->i_time = i_time;
newstate->next = NULL;
printf("initialized state:");
SVS_Debug_State(newstate);
if (svs_current_state.coun > 0)
{
laststate = SVS_Get_State(svs_current_state.count);
laststate->next = (void*)newstate;
} else
svs_current_state.states=newstate;
svs_current_state.count++;
}
int main()
{
int i_playfield[6][7] = {0};
// mark saves library as loaded here, but removed function, since it
// just sets svs_current_state.loaded (which is the global struct of
// type SVS_STATES) to 1
SVS_Add_State(i_playfield, 1, time(NULL));
i_playfield[0][0] = 2;
SVS_Add_State(i_playfield, 2, time(NULL));
return 0;
}
The actual problems I encountered while using the printf's and Debug_State calls in these functions:
- the i_time I give is printed out once in Add_State(), correctly. Means it is a legal time and stuff, but when printed out after creating the full state by using Format_State() the string is 50 percent to long and the last part is displayed twice, for example:
if the time is 12345678, it is displayed correctly while debugging in Add_State, but Format_State() displays 123456785678.
- second problem: the first state added works, more or less, fine. But after adding a second one, printing the first state (retrieved by using Get_State and formatted with Format_State) prints a mixture of two states, for example something like this:
state 1: {{0,0,0,0,0,0,0}{0,0,0,0,0,0,0}{0,0,0,0,0,0,0}...
{0,0,0,0,0,0}};1;123456785678
state 2: {{0,0,0,0,0,0}{0,0,0,0,0,0}...
{0,0,0,0,0,0}};2;1234567856785678,0}{0,0,0,0,0,0}...
Thanks for reading.

Answer 1

These calls
sprintf(text, text, ...
invoke undefined behaviour, as the target buffer and one of the other arguments overlap.
From the POSIX specs to sprintf():
If copying takes place between objects that overlap as a result of a call to sprintf() [...], the results are undefined.