The leading underscore on MacOS is part of the Mach-O standard [1]. This was inherited from a.out which really wasn't much of a standard per se but rather just

The leading underscore on MacOS is part of the Mach-O standard [1]. This was inherited from a.out which really wasn't much of a standard per se but rather just a collection of a.out implementations [2]. Mach-O (1987) predated ELF (1993) and the later ELF abandoned the underscore as unnecessary. [1] http://math-atlas.sourceforge.net/devel/assembly/MachORuntime.pdf http://math-atlas.sourceforge.net/devel/assembly/MachORuntim... [2] https://www.nasm.us/doc/nasmdoc9.html https://www.nasm.us/doc/nasmdoc9.html