Enum Visibility 

pub enum Visibility {
    Default,
    Hidden,
    Protected,
}

How far outside a shared library a name reaches.

A different question from Linkage and asked of a different linker. The linkage is what the static linker does with a name while it is building the output, and this is what the dynamic linker may do with it once that output is a shared library and is being loaded. A hidden name is still external as far as the static link is concerned, so two files in the same library reach each other by it; it is simply not in the dynamic symbol table afterwards.

Four strings are written and there are three answers, because internal is hidden plus a promise the program makes about never taking the address across a component boundary. Reading it as hidden gives less than was asked for, which is safe in the way -fstrict-aliasing is safe: every program correct under the stronger assumption is correct under the weaker one and nothing here derives anything from the difference. It is written down in spec/13-gnu-compat.md section 13.4 rather than left for someone to find in the output.

Variants

Default

In the dynamic symbol table and interposable, which is what a name gets when nothing said otherwise and what visibility("default") puts back after -fvisibility=hidden.

Hidden

Not in the dynamic symbol table, so nothing outside the library can name it.

Protected

In the dynamic symbol table, and a reference from inside the library binds to the definition inside it.

Trait Implementations

impl Clone for Visibility

fn clone(&self) -> Visibility

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Visibility

impl Debug for Visibility

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Visibility

impl PartialEq for Visibility

fn eq(&self, other: &Visibility) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Visibility