QMessageBox showing "Loading...."

Guapo

This is for restaurant app. Here in Brazil, all restaurants needs a device called SAT, connected to USB and the internet (to send all sales data to our beloved government) :). This device has its own library to create a sale invoice and send all data to government.
Load by hand is the way used to access the internal functions.
I don´t know another way to acess internal function from a .dll or .so .
My intention is open a screen to warning loading, because the user could think software is crashed. This library takes a several seconds to load.

jsulm

@Guapo said in Qmessagebox showing "Loading....":

I don´t know another way to acess internal function from a .dll or .so

Usually you link your app against a library to use it.
See http://doc.qt.io/qtcreator/creator-project-qmake-libraries.html

Guapo

@jsulm

when I tried to use this library, my first option was
at my .pro file

LIBS += -L"/mnt/midia4/prj/qt/Controle" -lDarumaFramework

But I cannot exec the internal function ( ex: rVerificarComunicacao_SAT_Daruma() ).

So, I received from the library owner a file to load it´s library and execute internal functions;

         bibliotecaDinamica = dlopen("./libDarumaFramework.so", RTLD_NOW);

This is working!

Today, I tried to include this line at my .pro file

LIBS += -L"/mnt/midia4/prj/qt/Controle" -lDarumaFramework -ldl

The library loading is during the aplication load....I can exec the internal function.

But this is all inside the Qt Creator....when I tried to exec my aplication from the CL, there is a segmentation fault.
I need more information, but this note is only to update you that I´m studying your hint.

tks

JonB

@Guapo said in Qmessagebox showing "Loading....":

         bibliotecaDinamica = dlopen("./libDarumaFramework.so", RTLD_NOW); 
But this is all inside the Qt Creator....when I tried to exec my aplication from the CL, there is a segmentation fault.

You need to check the return result of dlopen, as it may fail? Do you proceed to use bibliotecaDinamica without verifying its value?
./libDarumaFramework.so is a relative path; it must be found in the current directory. Is your current directory right for this while running from QtCreator, but something else when run from the command line? (I don't know what dlopen's behaviour is exactly, but you might be better with plain libDarumaFramework.so without the leading ./.) Have you put the library in the same directory as your executable, along LD_LIBRARY_PATH, or what?

Guapo

@JNBarchan

Yes...my library is on the same directory as my executable.

int main(int argc, char *argv[])
{
QApplication a(argc, argv);

qDebug()<< "inicio";

Login w;

w.show();

return a.exec();

}

The segmentation fault occours before "inicio". (only executing in CL at the directory where are all files....this code is ok executing inside the Qt Creator ).

jsulm

@Guapo If you want to execute your app outside of QtCreator you need to deploy it.
See http://doc.qt.io/qt-5/deployment.html

Guapo

@jsulm

I´m trying do execute my aplication only for tests. I´m executing it at the same folder as compiled.

When I do not use this line:

LIBS += -L"/mnt/midia4/prj/qt/Controle" -lDarumaFramework -ldl

It is possible execute it from CL.

When I need to make deployment, I´ve used linuxdeployqt script.

jsulm

@Guapo You can set LD_LIBRARY_PATH to point to the directory where this lib is and then start your app, see http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html

Guapo

@jsulm excuse me for this delay.

I found a performance problem and I need to fix it before.

I don´t know if it´s better open a new point to discuss.

This code has an answer in 1sec. This exec a function "EnviarDadosVenda" from my external lib.


#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <time.h>

#include "helpers.c"

int main(int argc, char *argv[]) 
{
	char * (*_EnviarDadosVenda) (int, char *, char *);

	void * handle;
	char * error;
	char * resposta;
	char cXML[5000];

	strcpy(cXML, "this is for XML");

	handle = dlopen ("./libsat.so", RTLD_LAZY);

	_EnviarDadosVenda = dlsym(handle, "EnviarDadosVenda");

    typedef char* (*funcao)(int, char*, char*);
    funcao runGui = (funcao)dlsym(handle, "EnviarDadosVenda");

    resposta = runGui(_sessao(),"12345678", cXML);  // 1sec to return data

	printf("======================================================\n");
	printf("\nExecutando funcao: _EnviarDadosVenda2\n");
	printf("\nRetorno: %s\n\n", (char *) resposta);
	printf("==++==================================================\n");
}

This function, running in qt, runs the same code in 16 secs. It´s the same function and the same lib.

char * EnviarDadosVenda2_libsat(int numerossessao, QString codigoativacao, QString pszXML){
    char * resposta;
    char cXML[1100];

    QDateTime agora=QDateTime::currentDateTime();
    char* _EnviarDadosVenda(int , char*, char*);

    strcpy(cXML, "My XML data");

    void* handle = dlopen("./libsat.so", RTLD_LAZY);

    typedef char* (*funcao)(int, char*, char*);
    funcao runGui = (funcao)dlsym(handle, "EnviarDadosVenda");

    qDebug() << "Vai executar EnviarDadosVenda2_libsat";

    resposta = runGui(numerossessao,"12345678", cXML);  // 16 seconds to return data

    qDebug() << "saiu EnviarDadosVenda2_libsat " << QDateTime::currentDateTime().toTime_t()-agora.toTime_t();

    return resposta;

}

jsulm

@Guapo Well, I don't know why this difference. Are you sure you pass exactly the same data to EnviarDadosVenda in both cases?
Also you wrote runGui takes 16 seconds to execute, but actually you measure time for copying the data, loading the library and resolving the symbol as well. Loading a library and resolving symbols can take some time, move

QDateTime agora=QDateTime::currentDateTime();

just before you call runGui.

Guapo

@jsulm yes...I´m sure the input data are the same at the both cases.

This xml string has more than 1000 bytes.

I made another test using this same function in a exclusive qt project that contain only this function and this function delay 1sec.

There is something in my project that retards the execution.

jsulm

@Guapo But did you change the way you measure the execution time? As I said in the code you posted you're measuring also library loading and symbol resolution.

Guapo

@jsulm I found the problem about 16 secs...it´s a bad implementation of EnviarDadosVenda ( external library )....there is a parameter ( random ) and if this number is greater than 999.999, EnviarDadosVenda takes 16 secs to answer...this is out of spec. I contacted the suplier to inform this issue.