Program with a GUI crashes when add .h and .cpp files

Pordo

Hello! I'm working on a program that uses multiple classes and a GUI. The thing is that I want to make an extra file where all the global variables, whose values are constant and are used in all the program. This file I did it by creating a header where I define the type of each variable and in a .cpp, I give it the value to each variable. The problem is that before creating the .h and .cpp files the program ran without any problems, but when I add these files the program crashes.

#ifndef CONSTANTESRADARGUI_H
#define CONSTANTESRADARGUI_H

//VARIABLES GLOBALES CON UN VALOR CONSTANTE
//se ponen todas las variables globales que se utilizan en todo el programa y su valor es constante
//las variables se inicializan en constantesradargui.cpp

//----------------------------
//parametros del radar
extern float freqM;         //frecuencia de muestreo, en m/s
extern int nBI;             //frecuencia de bearing increment BI, en Hz   no se usa
extern int nTRG;            //frecuencia de trigger TRG, en Hz    2037
extern int rpmHM;           //frecuencia del hearing mark HM, en rpm

//----------------------------
//parametros de la matriz M
extern int  nfilas;         //cantidad de filas de la matriz M
extern int numeroColumna;   //para modificar tamaño de la matriz (Lucas Pordomingo)
                            //numeroColumna=1 para cantidad de columnas calculadas con parametros del radar
                            //numeroColumna=2 para cantidad de columnas de 4096
                            //numeroColumna=3 para cantidad de columnas de 2096


//----------------------------
//parametros calculados a partir de los parametros del radar
extern int VelGiro;             //velocidad con la que gira el radar
extern int ncolumnas;           //numero de columnas de la matriz M, con los datos del radar
extern int tamano_columna;      //sirve para modificar distancia de graficado desde el centro del radar
//tamano_columna = 1/(ncolumnas/8183) y ncolumnas= int(round((1/nTRG)*(freqM*1000000))), para el caso de usar una matriz M cantidad de  columnas de acuerdo a los parametros del radar
//tamano_columna = 2 y ncolumnas = 4096, para el caso de usar una matriz M con 4096 columnas
//tamano_columna = 4 y ncolumnas = 2096, para el caso de usar una matriz M con 2096 columnas

//----------------------------
//constantes que se utilizan en varios lugares del programa
extern int niveles;        //colores
extern float area;         //area del pixel que se dibuja
extern float kmmilla;
extern float rmillamuestra;
extern float rfilaangulo;

#endif // CONSTANTESRADARGUI_H

#include<constantesradargui.h>

#include<math.h>

//----------------------------
//parametros del radar
float freqM= 16.666;         //frecuencia de muestreo, en m/s
int nBI= 2049;               //frecuencia de bearing increment BI, en Hz   no se usa
int nTRG= 2037;              //frecuencia de trigger TRG, en Hz    2037
int rpmHM= 25;               //frecuencia del hearing mark HM, en rpm

//----------------------------
//parametros de la matriz M
int nfilas= 4096;         //cantidad de filas de la matriz M
int numeroColumna= 1;    //para modificar tamaño de la matriz (Lucas Pordomingo)
                         //numeroColumna=1 para cantidad de columnas calculadas con parametros del radar
                         //numeroColumna=2 para cantidad de columnas de 4096
                         //numeroColumna=3 para cantidad de columnas de 2096

//----------------------------
//parametros calculados a partir de los parametros del radar
int VelGiro= (1/(rpmHM*0.02));;                        //velocidad con la que gira el radar
int ncolumnas= int(round((1/nTRG)*(freqM*1000000)));      //numero de columnas de la matriz M, con los datos del radar
int tamano_columna =1/(ncolumnas/8183);                   //sirve para modificar distancia de graficado desde el centro del radar
//tamano_columna = 1/(ncolumnas/8183) y ncolumnas= int(round((1/nTRG)*(freqM*1000000))), para el caso de usar una matriz M cantidad de  columnas de acuerdo a los parametros del radar
//tamano_columna = 2 y ncolumnas = 4096, para el caso de usar una matriz M con 4096 columnas
//tamano_columna = 4 y ncolumnas = 2096, para el caso de usar una matriz M con 2096 columnas

//----------------------------
//constantes que se utilizan en varios lugares del programa
int niveles = 5;        //colores
float area = 0.1;       //area del pixel que se dibuja
float kmmilla=1.852;
float rmillamuestra = (1 / (freqM * 1000000)) * (300000 / kmmilla);
float rfilaangulo= nfilas/360;

The errror is:
09:55:09: Starting /home/pc2/Descargas/build-Radar-Desktop-Debug/Radar...
09:55:10: /home/pc2/Descargas/build-Radar-Desktop-Debug/Radar crashed.

Christian Ehrlicher

Use a debugger and see where exactly it crashes.

Paul Colby

Hi @Pordo,

There's probably other things, but this line crashes with a floating-point exception on my machine:

int tamano_columna =1/(ncolumnas/8183);

The reason is that ncolumnas (from the preceding line) evaluates to 8182. And since all the values (both variables and literals) in that statement are integers, it evaluates like this:

int tamano_columna =1/(ncolumnas/8183);
                   =1/(8182/8183);
                   =1/trunc(0.99987779543);
                   =1/0;
                   =exception

You can fix this particular exception by making either ncolumnas or the 8183 literal a float or double; eg this does not crash for me:

int tamano_columna =1/(ncolumnas/8183.0);

But as @Christian-Ehrlicher said, the debugger is your friend :)

Cheers.

JonB

@Paul-Colby said in Program with a GUI crashes when add .h and .cpp files:

int tamano_columna =1/(ncolumnas/8183.0);

Good job for working through @Pordo's code to come to this! Indeed this will prevent the crash --- provided ncolumnas != 8183.0! But @Pordo may have a deeper logic problem in this statement.

Since the result is assigned to an int, there is a "limited" set of possibilities for what the 1 / something on the right-hand side will evaluate to anyway:

if something == 0, it will crash/be undefined.
if something >= 1, for any value of something then 1 / something will evaluate to 0 as a (truncated) integer.
if and only if 0 < something < 1 will it produce any int great than 0. Which means that for something, in the (ncolumnas/8183.0) expression ncolumnas needs to be a lot less than 8183.0 if this is the intention. Is it? Else I wonder what OP is expecting the value of tamano_columna to be?

Pordo

Hello, I was reading their answers and tried to comment a section of the code that uses the variable tamano_columa. The code compiles, so I confirm that the problem was there.
The variable is used to maintain a distance ratio on a graphic. I resolved it changing the variable type to float.
Thanks to everyone for their answers, they were helpful.

JonB

@Pordo said in Program with a GUI crashes when add .h and .cpp files:

I resolved it changing the variable type to float.

That sounds a lot more useful :)
Just a comment: consider using double instead of float for this, other constants and arithmetic. In C all floating point calculations are done in double-precision anyway (at least I think/thought this was the case). Using float instead of double throws away precision for no good reason. The only time I would use floats is to save space if I had millions of them....