c - Why doesn't `bar` in this code have static storage duration? -


code goes first:

#include <stdio.h>  void foo() {         static int bar; }  int main() {         bar++;         return 0; }

the compiler(clang) complains:

static.c:10:2: error: use of undeclared identifier 'bar'

shouldn't statement static int bar; in foo() give bar static storage duration, makes declared , initialized prior main function?

you confusing scope of variable storage duration.

as mentioned in c11 standard, chapter §6.2.1, scopes of identifiers,

  • for file scope

[...] if declarator or type specifier declares identifier appears outside of block or list of parameters, identifier has file scope, terminates @ end of translation unit. [...]

and function (or block) scope

[...] if declarator or type specifier declares identifier appears inside block or within list of parameter declarations in function definition, identifier has block scope, terminates @ end of associated block. [...]

in case, bar has file scope in foo(). not visible in main().

otoh, storage duration part,

an object identifier declared without storage-class specifier _thread_local, , either external or internal linkage or storage-class specifier static, has static storage duration. lifetime entire execution of program , stored value initialized once, prior program startup.

so, summarize, bar has static storage duration, scope limited foo() function. so, is

declared , initialized prior main() function

(before main() starts, exact) not visible , accessible in main().


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