Few limitations can be mentioned:
•
The alloca() function is machine dependent; its use is discouraged.
•
The alloca() function is slightly unsafe because it cannot ensure that the pointer returned points to a valid and usable block of memory. The allocation made may exceed the bounds of the stack, or even go further into other objects in memory, and alloca() cannot determine such an error. Avoid alloca() with large unbounded allocations.
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Since
alloca() modifies the stack at runtime, it causes problems to certain security features. See
security(8) for a discussion.