compilerruntime

Compiler runtime, often called a runtime library or CRT (C runtime), is the collection of support code that accompanies compiled programs to provide execution-time facilities not defined by the language standard alone. It typically includes startup and initialization routines, basic I/O support, memory management helpers, and services such as exception handling or stack unwinding, depending on the language and compiler.

The exact contents of a compiler runtime vary by language and toolchain. For C and C++ programs, the runtime works together with the standard C library (libc) and may rely on compiler-specific libraries such as libgcc or compiler-rt to implement builtins, runtime checks, and low-level support. In LLVM-based toolchains, compiler-rt provides sanitizer runtimes, builtins, and other low-level helpers used by Clang. Other language ecosystems supply their own runtimes aligned with their standard libraries and execution models.

Beyond traditional system libraries, compiler runtimes can include language-specific features such as exception handling mechanisms, garbage collection support, or runtime checks that are not part of the language syntax itself. Some runtimes also provide integration with tooling, debugging support, and platform abstraction layers to ease portability across operating systems.

Usage and deployment vary by platform and compiler. Runtimes can be linked statically into the executable or loaded dynamically at run time, and they are responsible for bridging the gap between language abstractions and the underlying OS and hardware. The concept of a compiler runtime has historical roots in early C compilers and remains a central part of modern language implementations.