C ++堆栈溢出未处理的大数组异常

Question

Right, having looked up this issue, I believe that it is caused because I have in my class definition wchar_t downloadedText[400000]; I have read solutions about how I should deal with this by using the new operator to assign the space, ie: wchar_t *downloadedText; downloadedText = new wchar_t[400000]; wchar_t *downloadedText; downloadedText = new wchar_t[400000];

However I need to write instances of the class to a file, and assigning the variable like above appears to use pointers to point to data stored in a way that does not get written to my file. It is this same reason why I cannot use std::vector .

I have read that another option I may have is that I can increase the size of the 'stack'. I use VS2010 as my IDE, and I located in my project properties > Linker > System 'Stack Commit Size', 'Stack Reserve Size', 'Heap Commit Size' and 'Heap Reserve Size' fields, but I am unsure if this is how I can deal with my issue, and if it is, what to correctly set the appropriate fields to.

Answer 1

If you must do it this way... You could just write the array explicitly, after writing out the object. eg.

write((char*)&myObjects[i]), sizeof(MyClass));
write((char*)downloadedText, sizeof(downloadedText[0]) * 400000);

And to read it back in:

read((char*)&myObjects[i]), sizeof(MyClass));
downloadedText = new wchar_t[400000];
read((char*)downloadedText, sizeof(downloadedText[0]) * 400000);

However, this is very fragile and prone to errors. Overwriting objects in memory as done by the read is at best bad form except perhaps if you're using a struct created explicitly for that purpose which would typically contain only PODs. As a minimum, note that you have to set the downloadedText member field after the read writes over it.

Answer 2

You can allocate the whole object with new operator in system heap but not on stack. In this case you can write this object to file in the same manner and have no troubles with stack overflow.

Answer 3

Yes, you can increase the stack size in Visual Studio with the linker option /STACK . This linker option is also editable with the project properties Stack Reserve Size and Stack Commit Size . It is enough to set the reserve size, the commit size is optional. Nevertheless you should also be able to use std::vector .

Answer 4

It sounds like you're fine with your current serialization strategy (make the object POD, and write it as a POD value). In that case, your question really is "how can a keep these objects from taking up too much space on the stack?" The answer: don't put them on the stack.

Allocate them with new. Or, preferably, wrap them in smart pointers of some kind.

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You have string-like data. It so happens that C++ offers a string class. In fact, since you're talking about wchar_t characters, you want to look at std::wstring (in the <string> header).