Compile time

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In computer science, compile time is the time when a compiler compiles code written in a programming language into an executable form. Compile time can also refer to the amount of time it takes for the compiler to compile a program.

A compiler will typically perform syntax checking, which includes type checks, scoping rule enforcement, amongst other checks; and other processes such as static binding, instantiation of templates, and optimization. Those are also called semantic analyses. Dynamic binding is typically done after compile time, but before runtime, usually by means of a program loader. Boundary checking of arrays can be done at compile time, but this is not commonly done as default.

Cross-compilers can produce programs which will run on a different CPU type, something which is often prohibitively slow at run time, though sophisticated implementations which perform efficient once-only conversion either at first execution and saved semi-permanently or once per execution do exist. Such implementations aren't as efficient as cross-compilation but they may be the only practical solution where a vendor does't produce a program on the desired CPU.

When an interpreter is used there may be no separation between compile time and run time. There may instead be a interpretation phase (often into bytecode) followed by execution, but performed by the same software and not exposed to the user. Compile time errors in a program that is normally compiled may instead be detected as runtime errors when interpreted instead.