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Jidong Xiao
2024-01-26 13:33:05 -05:00
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lectures/06_memory/README.md
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@@ -125,7 +125,7 @@ delete q;
## 6.3 Dynamic Allocation of Arrays ## 6.3 Dynamic Allocation of Arrays
- How do we allocate an array on the stack? What is the code? What memory diagram is produced by the code? - How do we allocate an array on the stack? What is the code? What memory diagram is produced by the code?
- Declaring the size of an array at compile time doesn’t offer much flexibility. Instead we can dynamically allocate an array based on data. This gets us part-way toward the behavior of the standard library vector class. Here’s an example: - Declaring the size of an array at compile time doesn’t offer much flexibility. Instead we can dynamically allocate an array based on data. Here’s an example:
<table> <table>
<tr> <tr>
@@ -161,14 +161,11 @@ array are not known until the program is executed and the the memory must be all
In fact, the expression a[i] is exactly equivalent to the pointer arithmetic and dereferencing expression *(a+i) In fact, the expression a[i] is exactly equivalent to the pointer arithmetic and dereferencing expression *(a+i)
which we have seen several times before. which we have seen several times before.
- After we are done using the array, the line: delete [] a; releases the memory allocated for the entire - After we are done using the array, the line: delete [] a; releases the memory allocated for the entire
array and calls the destructor (we’ll learn about these soon!) for each slot of the array. Deleting a dynamically array and calls the destructor for each slot of the array. Deleting a dynamically allocated array without the [] is an error (but it may not cause a crash or other noticeable problem, depending
allocated array without the [] is an error (but it may not cause a crash or other noticeable problem, depending
on the type stored in the array and the specific compiler implementation). on the type stored in the array and the specific compiler implementation).
- Since the program is ending, releasing the memory is not a major concern. However, to demonstrate - Since the program is ending, releasing the memory is not a major concern. However, to demonstrate that you understand memory allocation & deallocation, you should always delete dynamically allocated
that you understand memory allocation & deallocation, you should always delete dynamically allocated
memory in this course, even if the program is terminating. memory in this course, even if the program is terminating.
- In more substantial programs it is ABSOLUTELY CRUCIAL. If we forget to release memory repeatedly - In more substantial programs it is ABSOLUTELY CRUCIAL. If we forget to release memory repeatedly the program can be said to have a memory leak. Long-running programs with memory leaks will eventually
the program can be said to have a memory leak. Long-running programs with memory leaks will eventually
run out of memory and crash. run out of memory and crash.
- Play this [animation](https://jidongxiao.github.io/CSCI1200-DataStructures/animations/dynamic_memory/example2/index.html) to see what exactly the above code snippet does. - Play this [animation](https://jidongxiao.github.io/CSCI1200-DataStructures/animations/dynamic_memory/example2/index.html) to see what exactly the above code snippet does.