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().


Comments

Post a Comment

Popular posts from this blog

Redirect to a HTTPS version using .htaccess -

i need modify .htaccess file redirect urls https version without "www". http://example.com --> https://example.com http://www.example.com --> https://example.com https://www.example.com --> https://example.com this how .htaccess file looks like: rewriteengine on rewritecond %{request_filename} !-d rewritecond %{request_filename} !-f rewriterule ^(.*)$ redirect.php?id=$1&page=$2 [qsa,l] what modifications need make .htaccess in order forward https without "www"? it depends on doing current code. looks file called redirect trying display php page seo friendly url. think might confusing people. anyway, need , force https without www, need 1 more rule above. also second rule needs two capture groups in rewriterule test string because wanting 2 different values using $1 , $2 references. rewriteengine on #rediect www non www and/or http https --- combinations. rewritecond %{http_host} !^example\.com [nc,or] rewritecond %{https} !^...
Read more

Unlimited choices in BASH case statement -

consider simple bash snippet: case $option in 1) image=${options[0]%.tar} ;; 2) image=${options[1]%.tar} ;; 3) image=${options[2]%.tar} ;; 4) image=${options[3]%.tar} ;; *) echo "invalid option" exit 1 esac in real script numbers goes 30. makes pretty long. can somehow specify cases variable? something this: case $option in $i) image=${options[$(($i-1))]%.tar} any pointer appreciated. you can match against multiple patterns in single clause: case $option in 1|2|3: echo "$option one, 2 or three" ;; esac if still typing you, can use simple pattern matching: case $option in # following matches # - single-digit numbers 0-9 # - two-digit numbers starting either 1 or 2 # - number 30 [0-9]|[12][0-9]|30) image=${options[$(($option-1))]%.tar} ;; *) echo "invalid option" 1>&2 exit 1 esac
Read more

javascript - jQuery: Add class depending on URL in the best way -

i have html progress meter: <div class="col-md-3" style="margin-left: -20px;"> <div class="progress-pos active" id="progess-1"> <div class="progress-pos-inner"> login </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-2"> <div class="progress-pos-inner"> scan items </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-3"> <div class="progress-pos-inner"> confirm address </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-4"> <div class="progress-pos-in...
Read more