So, I'm working on Binary Trees and I need to move information from one node to another one (structs). The thing is that I have this function that uses strcpy to copy the names and surnames from one node to other node (both sent as pointers) and when I try to run that part of the code in the program, it crashes.
Here is the function that copies the info (It has to copy the info from nodo2 to nodo1):
void MoverDatos(Tarbol *nodo1, Tarbol *nodo2)
{
strcpy((*nodo1)->appat, (*nodo2)->appat);
strcpy((*nodo1)->apmat, (*nodo2)->apmat);
strcpy((*nodo1)->nombre, (*nodo2)->nombre);
(*nodo1)->matr=(*nodo2)->matr;
}
As it wasn't working that way, I tried to use this one instead:
void MoverDatos(Tarbol *nodo1, Tarbol *nodo2)
{
char cad1[20];
char cad2[20];
char cad3[20];
strcpy(cad1, (*nodo2)->appat);
strcpy(cad2, (*nodo2)->apmat);
strcpy(cad3, (*nodo2)->nombre);
strcpy((*nodo1)->appat, cad1);
strcpy((*nodo1)->apmat, cad2);
strcpy((*nodo1)->nombre, cad3);
(*nodo1)->matr=(*nodo2)->matr;
}
But it didn't work either. I don't know if I'm not setting the arguments the right way or if I need to use another function, so any help or sugestion would be great. Thanks in advance.
It does compile with those arguments. I'm not getting any error message, it just crash and says that "program.exe has stopped working".
This is the struct that I'm using:
typedef struct _tdato
{
long matr;
char nombre[20];
char appat[20];
char apmat[20];
struct _tdato *sig;
struct _tdato *ant;
struct _tdato *padre=NULL;
}Tdato;
typedef Tdato *Tarbol;
The crash comes when I trie to copy a char[ ] to nodo1.
Related
I'm try to make simple kernel module with multithreading.
So I'm using linux/kthread.h, kernel v. 5.2.11
Problem: I can't passing the char array into thread: Segmentation fault.
That's what I'm doing:
typedef struct {
int num;
char origin[MAXSTR]; //part of input for current thread
struct completion wait_for_thread; //completion struct
} kthread_arg;
Then:
struct task_struct *task;
static kthread_arg kta_first_thread;
kta_first_thread.num = 1;
strncpy(kta_first_thread.origin, dat1, MAXSTR );
//Here I have normal char array 'origin'
init_completion(&kta_first_thread.wait_for_thread);
task = kthread_run(&thread_function, (void*)&kta_first_thread, "one");
And after that I have the error. Moreover, if you remove the array from struct, then everything works.
I'm sure doing something wrong?
The args passed to kernel_run must be kmalloced, your args is in stack. I have met the same problem, your code should like this:
struct your_struct* test=NULL;
struct task_struct* t=NULL;
test=(struct your_struct*)kmalloc(sizeof(struct your_struct),GFP_KERNEL);
t=kthread_run(your_function,(void*)test,name);
I'm not even sure how to properly formulate question about this.
I'm writing a library where I have multiple implementations (multiple libraries out of one). I want to hide as much as possible, if not all, implementation details from client app, in order to write an app disregarding implementation details.
It's all fine when implementation is contained within one function. However, often I need to instantiate a struct from library, do something to it with a function from library, resume writing app as normal, and then return to a function from library with data from previous function from library.
Struct details are important ONLY to library functions. I don't need to see or touch those from client application apart from passing them around because of this.
So, is there a way to hide struct details from client app and still be able to use it or if there's another way of doing this by some form of encapsulation or maybe even some kind of data (globals?) visible only to library?
Here's my lame illustration example with code:
/*
library_private.h
*/
#if (A)
{
struct mystruct_t {
A *something;
}
}
#else
struct mystruct_t {
B *something;
}
#endif
/*
library_public.h
*/
struct mystruct_t;
/*
library.c
*/
struct mystruct_t* create() {
struct mystruct_t *handle = malloc(sizeof(struct mystruct_t));
return handle;
}
/*
client.h
*/
struct mystruct_t;
/* but, I need a definition, so I have to repeat either from library_private.h */
/*
client.c
*/
int main(int argc, char const *argv[]) {
struct mystruct_t *handle = create();
/*...*/
something(handle);
return 0;
}
Cast to a void * when returning and back to structure mystruct_t just after passing into a function. This is not great as you will loose some of the compiler type checking.
client.c (or client.h) should include library_public.h. There is no need to have the structure definition. Only its declaration struct mystruct_t; is enough to use pointers to the structure. Of course, you cannot access its members, but that is exactly what you want in this case.
I've got an issue with an assignment, but I'm not asking for help to do the assignment, just single problem.
My code is like this:
#include "linux/kernel.h"
#include "linux/unistd.h"
#include <linux/slab.h>
typedef _msg_t msg_t;
struct msg_t { /* members here */ };
static msg_t *bottom = NULL;
static msg_t *top = NULL;
int function_one (argA, argB) {
/* function is working, no need to show code*/
}
int function_two (argA, argB) {
/* function is working, so no need I guess to show the code*/
}
int main(int argc, char ** argv) {
char *in = "This is a testing message";
char msg[50];
int mlen;
function_one(in, strlen(in)+1);
mlen = function_two(msg, 50);
}
Here's the problem: When I do the make command from the directory, I get the error
/home/<username hidden by me>/dm510/linux-3.18.2/arch/um/os-linux/main.c:118:
multipli definition of 'main'
arch/um/kernel/built-in.o:
/home/<username hidden again>/dm510/linux-3.18.2/arch/um/kernel/file_i_created.c:60
first defined here"
What does this error mean? I only defined the main method one time in my own file
The message says you have (at least) two C files, main.c and file_i_created.c that are included in the build. Both have main() functions. (In C, the term is "function", not "method".) Remove one of those source files, or remove/rename the main() function in one of them.
You have multiple approaches here:
Usually there is only one main in a program. If so, decide, which is the actual main and rename the other one
If both mains are essential, you could try putting them in seperate namespaces
Really can't tell without seeing the file_i_created.c code though. Could be something else as well.
I'm running into an issue where my "TEST INSIDE BUILD" works but not "TEST OUTSIDE." A fragment of the code is here
command_t build_op_command(unsigned code, command_t comone, command_t comtwo)
{
commad_t s;
s=malloc(sizeof(*s));
switch(code)
{
case 5:
s->type=SEQUENCE_COMMAND;
...
}
s->status=-1;
s->input=NULL;
s->output=NULL;
s->u.command[0]=comone;
s->u.command[1]=comtwo;
printf("TEST INSIDE BUILD: %d and %s",s->u.command[0]->type, s->u.command[0]->u.word[0]);
s->u.word=NULL;
s->u.subshell_command=NULL; //not yet implemented
return s;
}
and
...
command_t op_command;
op_command=build_op_command(op_pop(op_s),comone,comtwo);
printf("TEST OUTSIDE: %d and %s",op_command->u.command[0]->type,op_command->u.command[0]->u.word[0]);
...
command_t is a pointer for struct command. I'm not quite sure why it would correctly inside the build function, but not work correctly outside of it. Any input would be greatly appreciated. I run into a segmentation fault, I've tried allocating space for s->u.word, but that didn't seem to help anything.
struct command
{
enum command_type type;
int status;
char *input;
char *output;
union
{
struct command *command[2];
char **word;
struct command *subshell_command;
} u;
};
typeder struct command *command_t;
You do not give enough information, post the definition of command_t.
u is probably a union:
s->u.command[0]=comone;
s->u.command[1]=comtwo;
printf("TEST INSIDE BUILD: %d and %s",s->u.command[0]->type, s->u.command[0]->u.word[0]);
After the first printf, you initialize other members of this union and override the command:
s->u.word=NULL;
s->u.subshell_command=NULL; //not yet implemented
The next printf report different contents.
All members of a union share the same location in memory, you cannot use more than one member at a time.
I'm playing with integrating the gssapi into node.js. Im not sure how to represent this:
The gss_init_sec_context function contains many struct based parameters, some of which are nested pretty deeply. For example this struct:
typedef struct gss_ctx_id_struct
{
gss_OID mech;
#ifdef USE_KERBEROS5
struct _gss_krb5_ctx_struct *krb5;
#endif
} gss_ctx_id_desc;
So based on this I'm guessing I need to implement some kind of Structure (with ref-struct) to represent the krb5 pointer (since kerberos5 is being used). So I looked at this _gss_krb_ctx_struct and saw this...
typedef struct _gss_krb5_ctx_struct {
Shishi *sh;
Shishi_ap *ap;
Shishi_tkt *tkt;
Shishi_key *key;
gss_name_t peerptr;
int acceptor;
uint32_t acceptseqnr;
uint32_t initseqnr;
OM_uint32 flags;
int reqdone;
int repdone;
} _gss_krb5_ctx_desc, *_gss_krb5_ctx_t;
Where Shishi is a pointer to a library, and shishi_ap appears to be a pointer to a function. I'm not sure how to implement these things in node-ffi. Can someone give me some guidance here?