How can I free memory used by malloc() outside a function? - c

Question

I am trying to free the memory allocated by my getSongInfo function, I have tried using a pointer to the function call but I get an error "cannt assign int to type int*" error. Any help would be great as the current way I have seems like it may work, but I might be completely wrong. Thanks!
Original Attempt:
int *memPtr = NULL
memPtr = getSongInfo(&fillPtr[arrayCounter], tempArtist[counter], tempSong[counter]);
Gives error!
Current Attempt:
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#pragma warning(disable:4996)
int getSongInfo(struct songInfo *pFillInfo, char *artistName, char *songName);
void printSongInfo(struct songInfo songList[10]);
struct songInfo {
char *songArtist;
char *songTitle;
};
int main(void)
{
struct songInfo *fillPtr;
struct songInfo songList[10];
fillPtr = &songList[0];
char tempArtist[10][30];
char tempSong[10][30];
int *memPtr = NULL;
int i = 0;
int counter = 0;
int arrayCounter = 0;
while (counter != 10)
{
printf("Please enter the artist name: ");
fgets(tempArtist[counter], sizeof(tempArtist[counter]), stdin);
tempArtist[counter][strcspn(tempArtist[counter], "\n")] = 0;
printf("Please enter the song name: ");
fgets(tempSong[counter], sizeof(tempSong[counter]), stdin);
tempSong[counter][strcspn(tempSong[counter], "\n")] = 0;
getSongInfo(&fillPtr[arrayCounter], tempArtist[counter], tempSong[counter]);
printf("Song and Artist Captured! \n");
counter++;
arrayCounter++;
}
printSongInfo(fillPtr);
free(fillPtr->songArtist);
free(fillPtr->songTitle);
}
int getSongInfo(struct songInfo *pFillInfo, char *artistName, char *songName)
{
pFillInfo->songArtist = (char*)malloc(strlen(artistName) + 1);
pFillInfo->songTitle = (char*)malloc(strlen(songName) + 1);
strcpy(pFillInfo->songArtist, artistName);
strcpy(pFillInfo->songTitle, songName);
return 1;
}
void printSongInfo(struct songInfo songList[10])
{
int counter = 0;
while (counter != 10)
{
printf("%-35s %-35s\n", songList[counter].songArtist, songList[counter].songTitle);
counter++;
}
}

Answer 1

Your getSongInfo function does not return a pointer, so attempting to put the return value into a variable and then free it is pointless. The pointers in question are inside the struct songInfo, specifically, the fillPtr variable (which is actually redundant, since songList and fillPtr point to the same location).
In addition, please be aware that strcspn will not always return a valid index. If it does not find a match, it will return the length of the first argument.
I think this is more like what you are trying to do:
int main(void)
{
const int numSongs = 10;
struct songInfo songList[numSongs];
char tempArtist[30];
char tempSong[30];
int i;
int newline_idx;
for (i = 0; i < numSongs; ++i)
{
printf("Please enter the artist name: ");
fgets(tempArtist, sizeof(tempArtist), stdin);
newline_idx = strcspn(tempArtist, "\n");
if (newline_idx < sizeof(tempArtist))
tempArtist[newline_idx] = 0;
printf("Please enter the song name: ");
fgets(tempSong, sizeof(tempSong), stdin);
newline_idx = strcspn(tempSong, "\n");
if (newline_idx < sizeof(tempSong))
tempSong[newline_idx] = 0;
getSongInfo(&songList[i], tempArtist, tempSong);
printf("Song and Artist Captured! \n");
}
for (i = 0; i < numSongs; ++i)
{
free(songList[i].songArtist);
free(songList[i].songTitle);
}
}
You might consider separating the code for free()ing each struct into its own function.
You might also consider heeding that compiler warning instead of ignoring it, as Bodo commented. Careless handling of strings from stdin is dangerous.