TCC (Tiny C Compiler) is small, fast, unlimited, and safe. You can compile and execute C code everywhere (e.g., on rescue disks). It generates optimized x86 code, and can compile, assemble, and link several times faster than 'gcc -O0'. Any C dynamic library can be used directly. It includes an optional memory and bounds checker, and bounds-checked code can be mixed freely with standard code. C script is also supported--just add '#!/usr/bin/tcc' at the first line of your C source, and execute it directly from the command line.
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