Why do some include guards have a defined value? -



Why do some include guards have a defined value? -

usually when using include guards write them so:

#ifndef filename_h #define filename_h ... #endif // filename_h

now in librarys i've seen like:

#ifndef filename_h #define filename_h 1 ... #endif // filename_h

after reserach didn't find reason why include-gurad needed initialized.

is there reason doing this?

though i've never seen such compiler, i've been told "empty" define regarded not defined. i'm interested in compiler behaves so.

even c89 states: 3.8.1 conditional inclusion constraints

the look controls conditional inclusion shall integral constant look [...] of form

defined identifier

defined ( identifier )

which evaluate 1 if identifier defined macro name (that is, if predefined or if has been subject of #define preprocessing directive without intervening #undef directive same subject identifier), 0 if not.

include include-guards

Comments

Post a Comment

Popular posts from this blog

php - Android app custom user registration and login with cookie using facebook sdk -

php - Android app custom user registration and login with cookie using facebook sdk - i developing android application in users need register , log in using facebook. approximately, flow. open app first time, authenticate facebook, data, send info server create them business relationship in application, start session new business relationship in server, cookie perform later interactions. so far good. what need know wich info have send server, can able identify users when log in seccond time. because need start session in server , send cookie android app farther interactions. i'm using php server side language. i thinking getting getaccesstoken() in android facebook sdk, pass server on business relationship creation , storing in android app. but can't manage how login users on sec time utilize app. any suggestions ? in advance ! to uniquely identify user within app, should create request /me , user's id. guaranteed unique , remain con
Read more

django - Access session in user model .save() -

django - Access session in user model .save() - is possible access current session in user model .save()? pseudo code of want achieve: # users.models.py def save(self, *args, **kwargs): created = true if self.pk: created = false super(abstractuser, self).save(*args, **kwargs) # post-save if created: look_for_invite_in_session_and_register_if_found(self, session) seems wrong in architecture. shouldn't access request in models layer. work request must done in view. can this: user, created = abstractuser.objects.get_or_create(name=name) if created: look_for_invite_in_session_and_register_if_found(user, request.session) django session
Read more

php - .htaccess Multiple Rewrite Rules / Prioritizing -

php - .htaccess Multiple Rewrite Rules / Prioritizing - here current htaccess file: rewriteengine on rewritecond %{http_host} !^www\.website\.com [nc] rewritecond %{http_host} ([^.]+)\.website\.com [nc] rewriterule ^(.*)$ http://www.website.com/gotourl.php?urlid=?%1 [l] rewriterule ^(\w+)$ ./gotourl.php?urlid=$1 [nc,l] rewriterule ^(\w+)/$ ./gotourl.php?urlid=$1 [nc,l] the website in question url shortener i'm working on testing/developing , personal use. above code may not ideal i'm not familiar .htaccess , made via googling , testing. want url shortening aspect: http://website.com/1234 -> http://website.com/gotourl.php?urlid=1234 http://website.com/1234/ -> http://website.com/gotourl.php?urlid=1234 the problem cannot figure out how ignore directories. want specific directories go specific pages: http://website.com/img (or) http://website.com/img/ -> http://website.com/img.php http://website.com/img/1234 (or) http://website.com/
Read more