emRun / emRun++ / emFloat

SEGGER emRun is a complete C runtime library specifically designed and optimised for GCC/LLVM-based toolchains and embedded systems, delivering dramatically smaller code and faster execution than the standard newlib/newlib-nano libraries that ship with most Arm and RISC-V toolchains. emRun++ extends coverage to C++ runtime needs, while emFloat provides an IEEE 754 compliant floating-point library that achieves FPU-like performance in pure software, critical for microcontrollers without a hardware floating-point unit. Together, these three libraries form a drop-in replacement for the default runtime that can cut ROM usage in half and multiply execution speed without any source code changes.

Performance Benchmarks

Independent benchmarks on RISC-V 32-bit targets show the scale of improvement over GCC/newlib:

Benchmark	emRun	newlib	Improvement
Floating-point arithmetic	1,097 cycles	1,907 cycles	1.7x faster
Integer arithmetic	251 cycles	1,042 cycles	4.2x faster
printf ROM (simple test)	4,392 bytes	9,552 bytes (nano)	2.2x smaller
printf RAM (simple test)	184 bytes	416 bytes (nano)	2.3x smaller

emRun achieves these gains through hand-optimised assembly routines for Arm (Cortex-M and 32-bit Cortex-A) and RISC-V (RV32M, RV64), customisable formatted I/O that excludes unused conversion specifiers, full localization and UTF-8 support linked only when used, and zero heap requirements. A generic ANSI C implementation covers additional architectures.

Adoption and Quality

emRun and emFloat have been adopted by leading silicon vendors including SiFive, Microchip, and Nuclei, and are integrated into SEGGER Embedded Studio and Rowley CrossWorks. The libraries are verified with over 450 test suites comprising millions of test cases, including corner-case validation for every function. Source code delivery and royalty-free licensing, with no viral open-source clauses or attribution requirements, make emRun suitable for commercial products in any market segment. Silicon vendor buyout licences are also available for companies that want to bundle the runtime with their own toolchain distribution.