what does this mean " error: ISO C++ forbids declaration of --- with no type?

[qtlinuxnewbie]

actually it is sampleThread only

[Kumosan]

actually it is sampleThread only

??? Pardon? I don't understand.

It is either:
QThread *newThread;
or:
sampleThread *newThread;

You don't have a class 'Thread'.

[qtlinuxnewbie]

may be i was not clear for u .
it is

sampleThread *newThread

sampleThread *newThread

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[squidge]

In the code you have posted, you use just "Thread", not "sampleThread".

[qtlinuxnewbie]

i changed the posted code to sampleThread and tried to build but i am getting the same error.

[wysota]

You have a loop in your includes - mainwindow.h includes sampleThread.h which again includes mainwindow.h. Use a forward declaration in mainwindow.h instead of including sampleThread.h or don't include mainwindow.h in the other file.