I'm confused, could anyone help me? | Together C & C++ | Page 1

unkempt loomBOT Feb 25, 2024, 5:07 PM

#

When your question is answered use !solved to mark the question as resolved.

Remember to ask specific questions, provide necessary details, and reduce your question to its simplest form. For tips on how to ask a good question use !howto ask.

carmine acorn Feb 25, 2024, 5:07 PM

#

The words you don't underestand, are in spanish, forget them

#

error:

login.c: In function ‘user_login’:
login.c:17:40: error: incompatible types when assigning to type ‘float’ from type ‘char *’
   17 |         for(i=0;i<meta;i++){usuario[i]=db_username;contrasena[i]=db_password;}
      |                                        ^~~~~~~~~~~
login.c:17:66: error: incompatible types when assigning to type ‘float’ from type ‘char *’
   17 |         for(i=0;i<meta;i++){usuario[i]=db_username;contrasena[i]=db_password;}
      |                                                                  ^~~~~~~~~~~
login.c:21:20: error: incompatible types when assigning to type ‘float’ from type ‘char *’
   21 |         usuario[i]=user_toprove;
      |                    ^~~~~~~~~~~~
login.c:22:23: error: incompatible types when assigning to type ‘float’ from type ‘char *’
   22 |         contrasena[i]=pass_toprove;
      |                       ^~~~~~~~~~~~
login.c: At top level:
login.c:48:5: error: expected identifier or ‘(’ before ‘return’
   48 |     return output;
      |     ^~~~~~
login.c:49:1: error: expected identifier or ‘(’ before ‘}’ token
   49 | }
      | ^

pliant goblet Feb 25, 2024, 5:08 PM

#

I mean the errors are pretty self-explanatory, no?

unborn iron Feb 25, 2024, 5:08 PM

#

usuario is of type float, and you try to put a char pointer into it

#

yeah

pliant goblet Feb 25, 2024, 5:08 PM

#

Also you should definetly change the way you format your code

carmine acorn Feb 25, 2024, 5:08 PM

#

pliant goblet I mean the errors are pretty self-explanatory, no?

Not for me

carmine acorn Feb 25, 2024, 5:08 PM

#

unborn iron usuario is of type float, and you try to put a char pointer into it

ohhh

carmine acorn Feb 25, 2024, 5:08 PM

#

pliant goblet Also you should definetly change the way you format your code

I know, trying to do it

#

thanks both

unborn iron Feb 25, 2024, 5:09 PM

#

👍

carmine acorn Feb 25, 2024, 5:10 PM

#

But asking, could i just change it to char and the thing work whitout a for?

#

I want to usuario get a especific value when a while is done

pliant goblet Feb 25, 2024, 5:10 PM

#

Your IDE should support an auto-formatting.
E.g. for CLion it's Ctrl + Alt + L or for VS Code it's Shift + Alt + F (Windows), Shift + Option + F (Mac), Ctrl + Shift + I (Linux)

unborn iron Feb 25, 2024, 5:10 PM

#

if you made it into a char then it would only have the first letter of the username

#

but you want to put the whole username inside the usuario right

carmine acorn Feb 25, 2024, 5:11 PM

#

pliant goblet Your IDE should support an auto-formatting. E.g. for CLion it's `Ctrl + Alt + L`...

this?

pliant goblet Feb 25, 2024, 5:11 PM

#

carmine acorn this?

Why are you using an online editor?

carmine acorn Feb 25, 2024, 5:12 PM

#

unborn iron but you want to put the whole username inside the usuario right

let me explain because i cannot underestand

I want to get a data from a db where it's a user and a password.

The user introduce user and password and the program checks

carmine acorn Feb 25, 2024, 5:12 PM

#

pliant goblet Why are you using an online editor?

Because visual studio code wont work

pliant goblet Feb 25, 2024, 5:12 PM

#

Online editors are great for short tests, but for actually programming I would always recommend an IDE

carmine acorn Feb 25, 2024, 5:12 PM

#

he doesnt wnat

carmine acorn Feb 25, 2024, 5:12 PM

#

pliant goblet Online editors are great for short tests, but for actually programming I would a...

recomend me one

#

online editor is bad as crap

#

but no other thing

pliant goblet Feb 25, 2024, 5:13 PM

#

CLion, VS or VS Code.

I've only ever used CLion and VS Code, but I've heard from many that VS is the best thing for Windows

#

Idk why VS Code doesn't work for you, probably because you didn't set it up correctly

unborn iron Feb 25, 2024, 5:13 PM

#

carmine acorn let me explain because i cannot underestand I want to get a data from a db wher...

float usuario[n];

Change To

char* usuario[n];

carmine acorn Feb 25, 2024, 5:13 PM

#

pliant goblet Idk why VS Code doesn't work for you, probably because you didn't set it up corr...

you gor it

carmine acorn Feb 25, 2024, 5:14 PM

#

pliant goblet CLion, VS or VS Code. I've only ever used `CLion` and `VS Code`, but I've heard...

I will try, thanks

carmine acorn Feb 25, 2024, 5:14 PM

#

unborn iron ```c float usuario[n]; ``` Change To ```c char* usuario[n]; ```

Okay

#

But i mean, could i do it other way?

#

because im seeing something

#

that could work

unborn iron Feb 25, 2024, 5:14 PM

#

try other way

#

👍

pliant goblet Feb 25, 2024, 5:14 PM

#

unborn iron ```c float usuario[n]; ``` Change To ```c char* usuario[n]; ```

Btw, when he does that then n == 0, so not only is this a VLA but it's also an array of length 0, which means accessing any index is UB

#

!vla

unkempt loomBOT Feb 25, 2024, 5:14 PM

#

pliant goblet !vla

What Is a VLA, and Why Is It "Bad"?

A Variable Length Array (VLA) is an array where the size is not constant and depends on a variable.

Example

int size = rand();
int vla[size]; // VLA of type int[size]
int not_vla[10]; // regular array of type int[10]
constexpr int size = 10;
int arr[size]; // also not a VLA, of type int[10]

Why Are VLAs "Bad"?

VLAs have poor compiler support and can lead to unsafe code. The core issue with VLAs is that the compiler doesn't know the size of the stack frame. Without warning flags like -Wvla, it can be easy to create a VLA by accident, even in C++ with some compilers.

Compiler Support

:white_check_mark: available since C99
:no_entry: not available in C++ at all
:no_entry: was never supported by MSVC
:warning: optional feature since C11
:warning: supported as non-standard extension by GCC, clang

pliant goblet Feb 25, 2024, 5:15 PM

#

Same for the contrasena array

pliant goblet Feb 25, 2024, 5:15 PM

#

carmine acorn this?

But yeah, for the online IDE this would be the button

unborn iron Feb 25, 2024, 5:15 PM

#

pliant goblet Btw, when he does that then `n == 0`, so not only is this a `VLA` but it's also ...

missed the part where n is zero, you right

#

oh shit

#

I just realized

#

this VLA thing

#

I was trying to research it but couldn't find info

#

this blurb helps a lot, thanks !

pliant goblet Feb 25, 2024, 5:17 PM

#

you're welcome ^^

unborn iron Feb 25, 2024, 5:17 PM

#

:D

#

I compile my code using gcc and my compiler was aok with using VLAs

#

and when I put in visual studio it told me that its not nice

pliant goblet Feb 25, 2024, 5:17 PM

#

:D

unborn iron Feb 25, 2024, 5:17 PM

#

so I've been mallocing() ever since for this case not knowing why

#

very epic

pliant goblet Feb 25, 2024, 5:17 PM

#

So accidently got onto the right track, nice

unborn iron Feb 25, 2024, 5:18 PM

#

yeah it was pure accident, I don't use visual studio at all

#

haha

#

I then checked my gcc options and it turned out i misspelled the Werror stuff I prepared so it wasn't complaining for anything

pliant goblet Feb 25, 2024, 5:19 PM

#

oh no, haha

#

!f

unkempt loomBOT Feb 25, 2024, 5:21 PM

#



#include <stdio.h>
#include <string.h>

int user_login(FILE* user) {
  char username[255], password[255], db_username[255], db_password[255],
      pass_toprove[255], user_toprove[255];
  int output = 0, n = 0, i = 0, meta = 0;
  float usuario[n], contrasena[i];
  if (fopen("user.txt", "r") == NULL) {
    return 3;
  } else {
    rewind(user);
  }

  printf("user: ");
  scanf(" %s", username);
  printf("pass: ");
  scanf(" %s", password);
  while (fscanf(user, "%s %s", db_username, db_password) != EOF) {
    // hay un problema, te pide con el mismo usuario sin cambiar que le
    // introduzcas una contraseña y se queda estacionado en el primero
    meta++;
    for (i = 0; i < meta; i++) {
      usuario[i] = db_username;
      contrasena[i] = db_password;
    }
  }
  for (i = 0; i < meta; i++) {
    usuario[i] = user_toprove;
    contrasena[i] = pass_toprove;
    while ((strcmp(username, user_toprove) != 0) ||
           (strcmp(password, pass_toprove) != 0)) {
      printf("Try again \n");
      printf("user: ");
      scanf(" %s", username);
      printf("pass: ");
      scanf(" %s", password);
    }
  }
  while ((strcmp(username, db_username) != 0) ||
         (strcmp(password, db_password) != 0)) {
    n++;
    if (n == 3) {
      printf("login limits reached. db stopped.\n");
      return 4;
    }
  }

  if ((strcmp(username, db_username) == 0) &&
      (strcmp(password, db_password) == 0)) {
    printf("Succefull loged in, %s.", username);
    output = 1;
  } else {
    return 2;
  }
}
return output;
}

/* re escribir esta parte */

ullenjoyer

pliant goblet Feb 25, 2024, 5:22 PM

#

Okay, and as you may be able to see now that the code is properly formatted you also have a massive problem because the return output line is entirely outside of the function

unkempt loomBOT Feb 25, 2024, 5:27 PM

#

@carmine acorn Has your question been resolved? If so, type !solved :)

pliant goblet Feb 25, 2024, 5:27 PM

#

Also scanf("%s", ...) is amongst the unsafest things you can do

#

https://sekrit.de/webdocs/c/beginners-guide-away-from-scanf.html

carmine acorn Feb 25, 2024, 5:31 PM

#

thanks both lads

#

i will try do one thing and then come back if it doesnt work

#

!solved

unkempt loomBOT Feb 25, 2024, 5:37 PM

#

Thank you and let us know if you have any more questions!

This thread is now set to auto-hide after an hour of inactivity

#I'm confused, could anyone help me?