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PO"this" pointer becomes null c++
primarykey
Id
15759614
data
AcceptedAnswerId
15760139
AnswerCount
1
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11
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CreationDate
2013-04-02T08:40:53.570
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0
LastActivityDate
2013-04-02T09:07:20.647
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0
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1726690
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0
PostTypeId
1
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1
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3750
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text
Body
I have a C++ Qt static library with two classes - dataprocthread and calcvalue. In the first one, when I call a method from an instance of calcvalue, pointer <code>this</code> (which references to dataprocthread class) suddenly becomes <code>null</code>. This is dataprocthread.h: <pre><code>class DataProcThread : public QThread { Q_OBJECT public: DataProcThread(int sarray[9], int val); signals: workDone(int result); private: int _sarray[9]; int _val; void run(); }; </code></pre> dataprocthread.cpp: <pre><code>DataProcThread::DataProcThread(int sarray[9], int val) { for (int x = 0; x < 9; x++) { _sarray[x] = sarray[x]; } _val = val; } void DataProcThread::run() { CalcValue* cv = new CalcValue(); int myval = 0; for (int i = 0; i < 100; i++) { myval = cv->processData(this->_val); if (this->_sarray[0] != myval) { //do something } } emit workDone(intValue); } </code></pre> calcvalue.h: <pre><code>class CalcValue { public: CalcValue(); int processData(int someval); }; </code></pre> calcvalue.cpp: <pre><code>CalcValue::CalcValue() { } int processData(int someval) { //do something and return int value } </code></pre> When I run this code, it suddenly recieves signal "Segmentation fault". Using debugger, I found that the problem in <code>DataProcThread::run()</code> function: when I call <code>cv->processData</code> function, all works good. But on the next line (<code>if (this->_sarray[0] != myval)</code>), <code>this</code> pointer becomes <code>null</code> (I can see it in Locals window), therefore, I can't access <code>this->_sarray</code> variable. In case it is important, that's how I start the thread (from another class outside my library): <pre><code>DataProcThread* thread = new DataProcThread(sarray, val); QObject::connect(thread, SIGNAL(workDone(int)), this, SLOT(collectWork(int))); thread->start(); </code></pre> What I am doing wrong?
Tags
<c++><qt><qthread>
Title
"this" pointer becomes null c++
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PostAcceptedAnswerId
1. PO
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 PTAnswer
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1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
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1. This table or related slice is empty.
UserOwnerUserId
1. USahawkthomas
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1. PL
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1. This table or related slice is empty.
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1. This table or related slice is empty.
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1. PO
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1. This table or related slice is empty.
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