Nested function
This is known as the funarg problem and is a key reason why nested functions was not implemented in some simpler languages as it significantly complicates code generation and analysis, especially when functions are nested to various levels, sharing different parts of their environment.The nested function technology allows a programmer to write source code that includes beneficial attributes such as information hiding, encapsulation and decomposition.Thus it is possible to return a function that is set to fulfill a certain task with little or no further parameters given to it, which can increase performance quite significantly.[2] A simple example in Pascal: The function F is nested within E. Note that E's parameter x is also visible in F (as F is a part of E) while both x and y are invisible outside E and F respectively.For this reason nested functions are not supported in some languages such as C, C++ or Java as this makes compilers more difficult to implement.A well known example of this is the GNU C implementation of C which shares code with compilers for languages such as Pascal, Ada and Modula.This implementation calls nested functions through a jump instruction placed on the machine stack at runtime.If a nested function is used in the development of a program, then the NX stack is silently lost, unless GCC is called with the ‑Wtrampoline option to alert of the condition.Software engineered using Secure Development Lifecycle often do not allow the use of nested functions in this particular compiler due to the loss of NX stacks.