mysql_real_escape_string() causing segmentation fault - mysql

Question

I'm working on a C program that uses the mysql.h library. This is the code:
int newproduct(){
char *name;//nombre del prducto
char *desc;//descripcion del producto
double price;//precio del producto
cprint("Agregar nuevo producto\n\n");
printf("Nombre del producto: ");
scanf("%s", &name);
printf("Descripcion: ");
scanf("%s", &desc);
printf("Precio: ");
scanf("%e", &price);
MYSQL *conn;
conn = mysql_init(NULL);
if (!mysql_real_connect(conn, server,
user, password, database, port, NULL, 0)) {
fprintf(stderr, "%s\n", mysql_error(conn));
exit(1);
}
char *rname = NULL;//string donde guardar el nombre con caracteres de escape
char *rdesc = NULL;
mysql_real_escape_string(conn,rname,name,strlen(name));//se realiza el real escape
mysql_real_escape_string(conn,rdesc,desc,strlen(desc));
/*
char *query;//donde guardar el query
snprintf(query,1000,"INSERT INTO productos (nombre,descripcion,stock,precio) VALUES( %s,%s, 0, %e)",rname,rdesc,price);//query a enviar
if (mysql_query(conn, query)) {//enviar el query
fprintf(stderr, "%s\n", mysql_error(conn));
exit(1);
}*/
mysql_close(conn);
return 0;
}
And this is the console execution
Agregar nuevo producto
Nombre del producto: a
Descripcion: a
Precio: 1
Segmentation fault (core dumped)
------------------
(program exited with code: 139)
Press return to continue
I'm sure that the mysql_real_escape_string is causing the segmentation fault because when I comment it the code works fine but it's my first time working with MySQL and I have no clue why this is failing. Besides that i was able to retrieve some info from the database so its not a connection error.
PD: cprint is a declared function that adds a header to the printf function containing mysql row data.

Answer 1

rname and rdesc are supposed to be buffers, not pointers to NULL. You must alloc the memory space first.
For instance:
char rname[1024];
char rdesc[1024];
mysql_real_escape_string(conn, rname, name, 1024);
mysql_real_escape_string(conn, rdesc, desc, 1024);
Also, the size of rname cannot be strlen(name), because the escape characters will require extra space. The required buffer may have to be up to four times bigger than the original string.

Answer 2

From the docs the to argument:
unsigned long mysql_real_escape_string(MYSQL *mysql, char *to, const char *from, unsigned long length)
^^^^^^^^
which in your case is rname and rdesc need to have space allocated to them. The documents specifically say:
You must allocate the to buffer to be at least length*2+1 bytes long.
You are also not using scanf correctly with name and desc since neither has space allocated to them. Something like the following would work:
char name[80];
scanf("%s", name);
If we go with the a size of 80 for name then following the document, the following would work for rname:
char rname[161] ;