malloc vs calloc

The three memory allocation statements you’ve shown:

arr = (int *)malloc(nx * sizeof(int));
arr = malloc(nx * sizeof(int));
arr = calloc(nx, sizeof(int));

all serve the purpose of dynamically allocating memory for an array of nx integers. However, there are key differences in terms of syntax, behavior, and intent:

*1. (int )malloc(nx * sizeof(int))

Type-casted malloc

• Allocates memory for nx integers.
• Does not initialize the allocated memory — it contains garbage values.
• The cast (int *) is not necessary in C, but is required in C++.

→ Best practice in C: Avoid casting malloc.

2. malloc(nx * sizeof(int))

Raw malloc without casting

• Standard usage in C — this is idiomatic and clean.
• Same behavior as above: allocates nx * sizeof(int) bytes.
• Memory is uninitialized — unpredictable content.

→ This is preferred in modern C code.