Now you're leaking memory every time that function is called.
On 14/09/12 15:42, Heidler, Kirstin (GE Oil & Gas) wrote: > Hi, > > thank you, I also found a different solution. I am not sure why it is > working, but it does. > I simply create the file object as a pointer to the file object like that: > QFile *file; > file = new QFile(fileName); > file->open(QIODevice::ReadOnly); > > Thank you for the hint. :) > Kirstin > > -----Ursprüngliche Nachricht----- > Von: interest-bounces+kirstin.heidler=ge....@qt-project.org > [mailto:interest-bounces+kirstin.heidler=ge....@qt-project.org] Im Auftrag > von Thomas McGuire > Gesendet: Freitag, 14. September 2012 13:56 > An: interest@qt-project.org > Betreff: Re: [Interest] Access Violation using QFile and QTextStream > > Hi, > > In the FileParser constructor, you create a QFile object on the stack. This > means that the QFile object will get destroyed when the constructor is done. > Then you create a QTextStream and pass that a pointer to the QFile. This > pointer will however point to invalid memory after the constructor has > finished, as the QFile will have been destroyed. > All further accesses to the QTextStream then internally try to use the > invalid pointer to the already destroyed QFile, which will cause a access > violation. > A solution here would be to make the QFile a member variable as well, so that > it has a longer lifetime than just in the constructor. > > Regards, > Thomas > > On Friday 14 September 2012 13:44:00 Heidler, Kirstin (GE Oil & Gas) wrote: >> Here is what I do: >> >> I open a File with QFile. Next I create a QTextStream for that file. >> This TextStream is saved in a member to my FileParsing-class. >> >> While still in the constructor everything works fine. I can access the >> TextStream, print it's device's size etc. >> >> The problem arises once my TestCase calls a function to read a line. >> >> In that function of my File-Parsing class nothing seems to be working. >> I want to use seek but that does not work. Printing the size also no >> longer works. >> >> When I run the application normally I don't get an error at all. The >> only thing that happens is, that only one testcase is executed (the >> default one, that should always pass). >> >> The testcase runner however does not notify me, that there was an error. >> >> When I debug the application I get a write access violation. (Code: >> 0xc0000005) at: 0x8, flags = 0x0; >> >> This sounds to me like the memory was somehow freed??? I don't >> understand why... >> >> >> >> Here are some code examples: >> >> The testfunction that does the calls: >> >> void FileParserTest::testNameReadCorrectly(){ >> >> FileParser parser = FileParser::FileParser( >> >> "C:/Users/108015407/Documents/DatenSolidAxle/Seite >> A/GE_TDGS_3.5_S56°.GE.20°-80°.ERA.600.2012.2.zeu.Takt 1.txt"); >> >> parser.readName(); >> >> QString name = "GE_TDGS_3.5_S56°.GE.20°-80°.ERA.600.2012.2.zeu"; >> >> QCOMPARE(parser.m_summary.getName(), name); >> >> } >> >> >> >> Relevant header of the parser: >> >> #ifndef FILEPARSER_H >> #define FILEPARSER_H >> #include "scanSummary.h" >> #include <iostream> >> #include <string> >> #include <QFile> >> #include <QString> >> #include <QTextStream> >> class FileParser >> { >> public: >> FileParser(char* fileName); >> ~FileParser(); >> ScanSummary m_summary; >> void readName(); >> >> protected: >> QTextStream *m_file; >> }; >> #endif // FILEPARSER_H >> >> >> >> >> The relevant functions: >> >> FileParser::FileParser(char *fileName){ >> >> QFile file; >> >> file.setFileName(fileName); >> >> if(!file.exists()){ >> >> std::cout << "File not exist" << std::endl; >> >> } >> >> bool succ = file.open(QIODevice::ReadWrite); >> >> std::cout << succ << std::endl; >> >> if(!succ){ >> >> std::cout << "Not Good!" << std::endl; >> >> } >> >> m_file = new QTextStream(&file); >> >> std::cout << m_file->device()->size() << std::endl; >> >> } >> >> FileParser::~FileParser(){ >> >> m_file->device()->close(); >> >> } >> >> >> >> void FileParser::readName(){ >> >> if(!m_file->device()){ >> >> std::cout << "Alarm..." << std::endl; >> >> } >> >> std::cout << "I got here: 4.05" << std::endl; //gets to this mark >> but not the next >> >> //std::cout << m_file->device()->size() << std::endl; //these two >> lines don't work either >> >> //std::cout << m_file->pos() << std::endl; >> >> bool succ = m_file->seek(0); >> >> std::cout << succ << std::endl; >> >> std::cout << "I got here: 4.1" << std::endl; >> >> QString line; >> >> std::cout << "I got here: 4.2" << std::endl; >> >> line = m_file->readLine(); >> >> std::cout << "I got here: 4.3" << std::endl; >> >> m_summary.setName(line); >> >> std::cout << "I got here: 4.4" << std::endl; >> >> } _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
