警告：数组元素超过 100

Question

I have a piece of code declaring an array.

#define MAX_ELEMENT 150
Struct_arr  arr_elem[MAX_ELEMENT];

Here Struct_arr is a structure. On compilation i am getting the warning for this later line as:

warning:array elements are more than 100

could someone please help me about this?

regards, vivG

Answer 1

That's almost certainly the result of a #warning directive in the code somewhere. C++ itself does not limit you to 99 array elements, this will be an artificial limit introduced for some reason.

My advice would be to search for that message and see if there's any comments close by which explain why that's a problem. Something like:

fgrep 'array has more than' *.c *.cpp *.h *.hpp

in as UNIX-like operating system would be a good starting point.

Answer 2

The warnings says that you're trying to allocate a big array on the stack. On typical linux system, the stack has 8Mb, so it can be quite easy to reach that limit (causing a segfault). This is why you have this warning.

As you tagged your question as C++, please notice that it's not very common to use C-style array in C++. You would rather use an

std::vector<Struct_arr> arr_elem(150);

This allocates a vector of 150 elements, but it can be dynamicaly resized, so if you allocated such a big array "just in case", then a std::vector is even more the way to go.

Last thing, just use plain old constants instead of macros, there is really no benefit from using them in this particular situation.