Reference 1
A technique to resolve unique names for programming entities in many modern programming languages.
Provides a way of encoding additional information in the name of a function, structure, class or another datatype in order to pass more semantic information from compilers to linkers.
Linker: To link different object code together, linker needs a great deal of information on each program entity. For example, to correctly link a function, it needs the function name, the number of arguments and their types, and so on.
C: distinguish pieces of code by function name only, ignoring any other information like parameter types or return types.
C++: distinguish by function name, parameter types, return type, and calling convention of a function. To implement this, additional information was encoded in the name of a symbol.
no function overloading, but have different calling conventions to be used when being called.
Compilers targeted at Microsoft Windows platforms support a variety of calling conventions.
A consistant mangling scheme across different language, allows subroutines in those languages to call or be called correctly.
Example of name mangling for C in Windows:
int _cdecl f (int x) {return 0;}
int _stdcall g (int y) {return 0;}
int _fastcall h (int z) {return 0;}
After compiled ni 32-bit compilers:
_f
_g@4
@h@4
Example 1. Before mangling:
int f (void) { return 1; }
int f (int) { return 0; }
void g (void) { int i = f(), j = f(0); }
After mangling:
int __f_v (void) { return 1; }
int __f_i (int) { return 0; }
void __g_v (void) { int i = __f_v(), j = __f_i(0); }
Example 2. Source code with mangled names in comments:
namespace wikipedia
{
class article
{
public:
std::string format (void);
/* = _ZN9wikipedia7article6formatEv */
bool print_to (std::ostream&);
/* = _ZN9wikipedia7article8print_toERSo */
class wikilink
{
public:
wikilink (std::string const& name);
/* = _ZN9wikipedia7article8wikilinkC1ERKSs */
};
};
}
Mangled symbols begin with _Z, followed by N for nested names, then a series of wikipedia::article::format becomes:
format: _ZN9Wikipedia7article6formatEv
print_to: _ZN9Wikipedia7article8print_toERSo
std::ostreamthe common C++ idiom:
#ifdef __cplusplus
extern "C" {
#endif
#ifdef __cplusplus
}
#endif
is used to avoid the name mangling by C++ compilers to be applied to C code.
If you could revise
the fundmental principles of
computer system design
to improve security...
... what would you change?