c - Can #ifndef ignore method or variable duplications? -


consider code.

#ifndef foo_h #define foo_h //code #endif

code can following cases

// case 1:  #define foo 0 
// case 2: void foo_method(){}; 
// case 3: int foo;

foo.h included in many c files. when compile case 1 without errors, other cases throw errors of duplication.

why when foo.h not concatenated c files except 1 while compiling?

about case 2:
should declare function signature, not body. has nothing pre-processor commands.

in header file (decleration only)

#if <condition> void foo(); #endif

in c file 

#if <condition> void foo(){    //body }  #endif

about case 3:
it's similar case 2, addition should declare variables in header file if extern , there no need declare them in header file otherwise. if are declared extern, need declared in c file without extern keyword:

in header file:

#if <condition> extern int bar; #endif

in c file:

#if <condition> int bar; #endif

Comments

Post a Comment

Popular posts from this blog

1111. appearing after print sequence - php -

morning, i have code takes string of shoe sizes, explodes , puts in table. code works , info displayed correctly on page after table there few 1's after table. i'm confused this. so table looks (in columns of 3 on webpage) available in following sizes: 3 4 5 6 9 10 111 here's codes, purpose of example $x = 3|4|6|10|9 function get_sizes_pipe($x) { $counter = 0; $splits = explode("|",$x); asort($splits); $x = print "<table class='greentable'>"; $x .= print "<thead><tr><th scope='col' colspan='3' abbr='starter'>available in following sizes:</th></tr></thead><tbody><tr>"; foreach ($splits $split) { $entry = print "<td>".$split."</td>"; if($counter == 2){ $entry .= print "</tr><tr>"; $counter =0; } else { $counter++; ...
Read more

excel - I can't get the attachement of the email PHP -

i have script connect imap , excel files. worked till today. 1 of our supplier script can't attached file. think there wrong decoding email. this code decoding if($attachments[$i]['is_attachment']) { $attachments[$i]['attachment'] = imap_fetchbody($this->_mbox,$email_number,$i); /* 4 = quoted-printable encoding */ if($flattenedparts[$i]->encoding == 3) { $attachments[$i]['attachment'] = base64_decode($attachments[$i]['attachment']); } elseif($flattenedparts[$i]->encoding == 4)/* 3 = base64 encoding */ { $attachments[$i]['attachment'] = quoted_printable_decode($attachments[$i]['attachment']); } } is there other ways decode email imap on php? the array of imap array ( [1] => stdclass object ( [type] => 0 [encoding] => 0 [ifsubtype] => 1 [subtype] => plain [ifdescription] => 0 [ifid] => 0 [lines] ...
Read more

node.js - Express and Redis - If session exists for this user, don't allow access -

i using redis , express this: // app.js var redis = require('redis'), redisclient = redis.createclient(), session = require('express-session'), redisstore = require('connect-redis')(session); session = session({ store: new redisstore({client: redisclient}), secret: 'secretkey', resave: true, saveuninitialized: true }) app.use(session); in index route file, set user session this: req.session.user = user; when user comes (or opens tab), how detect how many sessions having , block him access if has 1 active session? express-session working via cookies. had cookie named session sessionid. tabs inside browsed share cookies , can't rely on cookies if want strict working via 1 browser tab. you need create own sessions each opened browser tab. generating tabid @ client side , saving {userid, tabid} redis or can use websockets ( http://socket.io/ ) that, little overhead, doing want
Read more