fvisibility

Specifies the default visibility for global symbols or the visibility for symbols in a file.

IDE Equivalent

None

Architectures

IA-32, Intel® EM64T, Intel® Itanium® architecture

Syntax

Linux:	-fvisibility=keyword -fvisibility-keyword=file
Windows:	None

Arguments

keyword	Specifies the visibility setting. Possible values are:
	default	Sets visibility to default.
	extern	Sets visibility to extern.
	hidden	Sets visibility to hidden.
	internal	Sets visibility to internal.
	protected	Sets visibility to protected.

file

Is the pathname of a file containing the list of symbols whose visibility you want to set. The symbols must be separated by whitespace (spaces, tabs, or newlines).

Default

-fvisibility=default

The compiler sets visibility of symbols to default.

Description

This option specifies the default visibility for global symbols (syntax -fvisibility=keyword) or the visibility for symbols in a file (syntax -fvisibility-keyword=file). The second syntax form overrides the first.

Note

These two ways to explicitly set visibility are mutually exclusive. You may set visibility in the declaration, or specify the symbol name in a file, but not both.

Option	Description
-fvisibility=default -fvisibility=default=file	Sets visibility of symbols to default. This means other components can reference the symbol, and the symbol definition can be overridden (preempted) by a definition of the same name in another component.
-fvisibility=extern -fvisibility=extern=file	Sets visibility of symbols to extern. This means the symbol is treated as though it is defined in another component. It also means that the symbol can be overridden by a definition of the same name in another component.
-fvisibility=hidden -fvisibility=hidden=file	Sets visibility of symbols to hidden. This means that other components cannot directly reference the symbol. However, its address may be passed to other components indirectly.
-fvisibility=internal -fvisibility=internal=file	Sets visibility of symbols to internal. This means the symbol cannot be referenced outside its defining component, either directly or indirectly.
-fvisibility=protected -fvisibility=protected=file	Sets visibility of symbols to protected. This means other components can reference the symbol, but it cannot be overridden by a definition of the same name in another component.

Alternate Options

None

Example

Assume that a file named prot.txt contains symbols a, b, c, d, and e. Now, consider the following:

-fvisibility-protected=prot.txt

This option sets protected visibility for all the symbols in the file.