Dynamic Dead Code Elimination
Dead code is normally considered dead unconditionally. Therefore, it is reasonable attempting to remove dead code through dead code elimination at compile time.
However, in practise it is also common for code sections to represent dead or unreachable code only under certain conditions, which may not be known at the time of compilation. Such conditions may be imposed by different runtime environments (for example different versions of an operating system, or different sets and combinations of drivers or services loaded in a particular target environment), which may require different sets of special cases in the code, but at the same time become conditionally dead code for the other cases. Also, the software (for example, a driver or resident service) may be configurable to include or exclude certain features depending on user preferences, rendering unused code portions useless in a particular scenario. While modular software may be developed to dynamically load libraries on demand only, in most cases, it is not possible to load only the relevant routines from a particular library, and even if this would be supported, a routine may still include code sections which can be considered dead code in a given scenario, but could not be ruled out at compile time, already.
The techniques used to dynamically detect demand, identify and resolve dependencies, remove conditionally dead code, and recombine the remaining code at load or runtime are called dynamic dead code elimination.
Most computer languages, compilers and operating systems offer no or little more support than dynamic loading of libraries and late linking, therefore software utilizing dynamic dead code elimination is very rare.
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