Description |
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You can use only one storage-class specifier in a declaration.
The typedef keyword is listed as a storage-class specifier
because it is syntactically similar to one.
The keyword extern affects the linkage of a function or object name.
If the name has already been declared in a declaration with file
scope, the linkage will be the same as in that previous declaration.
Otherwise, the name will have external linkage.
The static storage-class specifier may appear in declarations
of functions or data objects. If used in an external declaration
(either a function or a data object), static indicates that the name cannot be referenced by
other translation units. Using the static storage class in this way allows translation units
to have collections of local functions and data objects that are
not exported to other translation units at link time.
If the static storage class is used in a declaration within
a function, the value of the variable is preserved between invocations
of that function.
The auto storage-class specifier is permitted only in the
declarations of objects within blocks. An automatic variable is
one that exists only while its enclosing block is being executed. Variables
declared with the auto storage-class are all allocated when a function
is entered. Auto variables that have initializes are initialized
when their defining block is entered normally. This means that auto variables with initializes are not initialized
when their declaring block is not entered through the top.
The register storage class suggests that the compiler store
the variable in a register, if possible. You cannot apply the & (address-of) operator to register variables.
If no storage class is specified and the declaration appears
in a block, the compiler defaults the storage duration for an object
to automatic. If the declaration of an identifier for a function has
no storage-class specifier, its linkage is determined exactly as
if it were declared with the extern storage-class specifier.
If no storage class is specified and the declaration appears
outside of a function, the compiler treats it as an externally visible
object with static duration.
