Name mangling

Learn name mangling and C++ symbol names.

Name mangling

Name mangling is the compiler encoding the function signature into the symbol name. Because C++ supports overloading and namespaces, the same name foo can appear multiple times; the linker needs the signature embedded in the name to tell them apart.

Example: int add(int, int) becomes _Z3addii in the Itanium ABI. Here _Z is the prefix, 3 the name length, add the name, ii two int parameters. double add(double, double) becomes _Z3adddd; different signature, different symbol.

Mangling notation

Itanium mangling codes: v=void, i=int, d=double, b=bool, c=char. The name is prefixed with its length: 3foo = foo.

Namespaces are wrapped with N...E: ns::bar() → _ZN2ns3barEv. Here N opens, 2ns is ns (length 2), 3bar is bar (length 3), E closes, v is the void parameter. Each signature maps to one symbol.

Exercise Write the add function

Write int add(int a, int b) with body return a + b;. In main write std::cout << add(3, 4);.

Show example solution

#include <iostream>

int add(int a, int b) {
    return a + b;
}

int main() {
    std::cout << add(3, 4);
    return 0;
}

Test yourself

Complete the body

int add(int a, int b) { return ____; }

Show answer

int add(int a, int b) { return a + b; }

Why does C++ mangle names?
```
int add(int, int);
double add(double, double);
```
- To shrink class size
- To speed up the program
- To hide the code
- For overloading and namespaces
Show answer

For overloading and namespaces — Mangling separates same-named different signatures at the linker.
Match each signature to its mangled symbol

add(int, int)

_Z3addii
add(double, double)

_Z3adddd
foo()

_Z3foov
ns::bar()

_ZN2ns3barEv

Next lesson: Itanium ABI

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