How different compilers mangle the same functions

There isn't a standard scheme by which even trivial C++ identifiers are mangled, and consequently different compiler vendors (or even different versions of the same compiler, or the same compiler on different platforms) mangle public symbols in radically different (and thus totally incompatible) ways. Consider how different C++ compilers mangle the same functions:
Compiler 	void h(int) 	void h(int, char) 	void h(void)
Intel C++ 8.0 for Linux 	_Z1hi 	_Z1hic 	_Z1hv
HP aC++ A.05.55 IA-64 	_Z1hi 	_Z1hic 	_Z1hv
IAR EWARM C++ 5.4 ARM 	_Z1hi 	_Z1hic 	_Z1hv
GCC 3.x and 4.x 	_Z1hi 	_Z1hic 	_Z1hv
GCC 2.9x 	h__Fi 	h__Fic 	h__Fv
HP aC++ A.03.45 PA-RISC 	h__Fi 	h__Fic 	h__Fv
Microsoft Visual C++ v6-v10 (mangling details) 	?h@@YAXH@Z 	?h@@YAXHD@Z 	?h@@YAXXZ
Digital Mars C++ 	?h@@YAXH@Z 	?h@@YAXHD@Z 	?h@@YAXXZ
Borland C++ v3.1 	@h$qi 	@h$qizc 	@h$qv
OpenVMS C++ V6.5 (ARM mode) 	H__XI 	H__XIC 	H__XV
OpenVMS C++ V6.5 (ANSI mode) 	CXX$__7H__FI0ARG51T 	CXX$__7H__FIC26CDH77 	CXX$__7H__FV2CB06E8
OpenVMS C++ X7.1 IA-64 	CXX$_Z1HI2DSQ26A 	CXX$_Z1HIC2NP3LI4 	CXX$_Z1HV0BCA19V
SunPro CC 	__1cBh6Fi_v_ 	__1cBh6Fic_v_ 	__1cBh6F_v_
Tru64 C++ V6.5 (ARM mode) 	h__Xi 	h__Xic 	h__Xv
Tru64 C++ V6.5 (ANSI mode) 	__7h__Fi 	__7h__Fic 	__7h__Fv
Watcom C++ 10.6 	W?h$n(i)v 	W?h$n(ia)v 	W?h$n()v

Notes:

    The Compaq C++ compiler on OpenVMS VAX and Alpha (but not IA-64) and Tru64 has two name mangling schemes. The original, pre-standard scheme is known as ARM model, and is based on the name mangling described in the C++ Annotated Reference Manual (ARM). With the advent of new features in standard C++, particularly templates, the ARM scheme became more and more unsuitable — it could not encode certain function types, or produced identical mangled names for different functions. It was therefore replaced by the newer "ANSI" model, which supported all ANSI template features, but was not backwards compatible.
    On IA-64, a standard ABI exists (see external links), which defines (among other things) a standard name-mangling scheme, and which is used by all the IA-64 compilers. GNU GCC 3.x, in addition, has adopted the name mangling scheme defined in this standard for use on other, non-Intel platforms.
    The Visual Studio and Windows SDK include the program undname which prints the C-style function prototype for a given mangled name.
    On Microsoft Windows the Intel compiler uses the Visual C++ name mangling for compatibility.[1]