Is there any way to determine the size of a C
How would the compiler know what the size of p is? The root of the problem is that there are no real arrays in C or in C++. There are only pointers, and there is patagonia down vest closeout2no way for the compiler or the program itself to know whether a pointer points to the beginning of a chunk of memory allocated by new, or to a single object, or to some place in the middle of a chunk of memory allocated by new.
One reason for this is that C and C++ leave memory management to the programmer and to the operating system, which is also why they do not have garbagepatagonia outlet new england collection. Implementation of new and delete is not part of the C++ standard, because C++ is meant to be used on a variety of platforms, which may manage their memory in very different ways. It may be possible to let C++ keep track of all the allocated arrays and their sizes if you are writing a word processor for apatagonia men's better sweater ebay windows box running on the latest Intel CPU, but it may be completely infeasible when you are writing an embedded system running on a DSP.
There is no really good reason why not that I m aware of. Probably, the size was considered an implementation detail, and best not exposed. Note that when you say malloc(1000), there is no guarantee that the block returned is 1000 bytes only that it s at least 1000 bytes. Most likely it s about 1020 (1K minus 4 bytes for overhead). In that case, the 1020 size is the important one for the run time library to remember. And of course, that would change between patagonia down vest closeoutimplementations.
Which is why the Standards committee added std:vector, which does keep track of it exact size.
C++ decided to add new to do a typesafe malloc, than new must know both size e numbers of elements for calling ctors, so delete for calling dtors. In the early days you have to actually pass to delete the numbers a objects you passed to new.
string p = new string[5];
delete[5] p;
However they thought that if use new[] the overhead of a number was small. So they decided that new[n] must remember n and pass it to delete. There are three main ways to implement it.
keep a hash table of pointer to size
wrote it directly near the vector
do something completely different
Maybe is possible to obtain the size like that:
size_t p = new size_t[10];There is no portable way of determining the size of a dynamically allocated array in C++ given only its pointer. C++ is made to be very flexible and to give power to the user. by adding a required size header. Not requiring a header allows for a lot more flexibility.
As one example, consider a string implemented as a char array. It s common to use pointers into the middle of the array to pick out substrings. As an example, see the strtok function in the standard C library. If some header were required to be embedded just before each array, you d need to trash portions of the array before the substring.
An alternative way to handle the headers would be to have array headers in one block of memory and have thpatagonia rain coat reviewsem point to the raw array memory elsewhere. In many situations, this would require two pointer lookups for each reference, which would be a big drag on performance. There are ways of overcoming these deficiencies, but they add complexity and reduce implementation flexibility.
The std::vector template is my favorite way of keeping the size of an array bound to the array itself.
C is portable assembly language with a better syntax.
In general, no. Arrays in C and C++ are just blocks of memory with no bookkeeping information attached. Without storing the length of the array in memory, and adding overhead to do so, it is impossible in the general case.
There is an exception for arrays that are statically allocated. For instance, if you declare: int a[50] then sizeof(a) will work. This is possible because the [50] is part of the static type of the array: it is known to the compiler. sizeof is interpreted at compile time.
However, if you create a pointer: int p = a, then sizeof(p) will return the size of the pointer as you mention, not the size of the array, because the compiler does not kpatagonia down vest closeout0now what p poipatagonia discount code vitacostnts to.
Unfortunately, this is not possible. In C and C++, it is the responsibilipatagonia down vest closeout1ty of the programmer to remember of the length of an array since array length is not stored anywhere. Delete[] and free() does remember the size of the allocated block but they might allocate more memory than requested so their internal data structures storing the sizes of allocated memory blocks might not give you the exact size of the your array.
Note that C++ STL vectors, which are basically arrays wrapped in a class with some helper functions, do store the patagonia everlong review under the domelength of the array so if you really need this functionality, you could just use vectors.
A C++ array is nothing more than a collection of objects which are stored in a contiguous memory region. Since there are no holes betweeen them (padding is inside objects), you can find the next element of an array by simply incerementing the pointer. At CPU level, this is a simple adjustment. C++ only inserts a sizeof(element) multiplier.
Note thapatagonia down vest closeout3t implementations may choose to implement fat pointers which contain array bounds. They d need to be twice as big, as you d need to link to some kind of array bound descriptor . As a side effect, on such implementations you could be able to call delete [] (1+new int[5]);
You could just create an extra element of the array and then apply the most unlikely number that will be stored in the array. Then you can determine the number of elements through some function by passing that number.
In the case of declaring and initializing an array at the moment of creation, you can then scan it and then generate a number that does not match any of the elements of the array. But ipatagonia guide pants xoxof you then modify one of the elements, you will not know if that elemenpatagonia guide pants 2 beltt stores the same value as thepatagonia guide pants 44x29 last element, so you will then have to generate a new number to store in the last element. patagonia hiking boots how to buyGoing through all that, you might as well just store the total number of elements at the moment of creation in a variable. And that will probably be the case if you only use the array within a function.
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