c++ - Strange code that compiles with g++ -


the following code compiles g++ 4.8.1:

int main() {     int(*)(); }

it looks simple declaration of pointer function:

int(*f)();

it doesn't compile clang 3.4 , vc++ 2013.

is compiler bug or 1 of dark places of standard?

list of similar strange code pieces compile fine g++ 4.8.1 (updated):

  1. int(*)();

  2. int(*);

  3. int(*){};

  4. int(*());

live example these strange code pieces.

update 1: @ali added interesting information in comments:

all 4 cases give compile error clang 3.5 trunk (202594) , compile fine gcc 4.9 trunk (20140302). behavior same -std=c++98 -pedantic, except int(*){}; understandable; extended initializer lists available -std=c++11.

update 2: @cantchooseusernames noted in his answer still compile fine initialization , no assembly generated them g++ (neither nor without initialization) without enabled optimization:

  1. int(*)() = 0;

  2. int(*) = 0;

  3. int(*){} = 0;

  4. int(*()) = 0;

live example initializations.

update 3: surprised find int(*)() = "hello, world!"; compiles fine, (while int(*p)() = "hello, world!"; doesn't compile, of course).

update 4: fantastic int(*){} = hello, world!; compiles fine. , following extremely strange piece of code, too: int(*){}() = -+*/%&|^~.,:!?$()[]{}; (live example).

update 5: @zwol noted in his comment

this , number of related syntactic problems being tracked gcc bug 68265.

according c++ standard (p. #6 of section 7 declarations)

6 each init-declarator in init-declarator-list contains 1 declarator-id, name declared init-declarator , hence 1 of names declared declaration

so compiler bug.

the valid code example (apart function pointer declaration showed you) though can not compile ms vc++ 2010.

int(*p){};

it seems compiler using testing allows declarations without declarator-id.

also take account following paragraph of section 8.1 type names

1 specify type conversions explicitly, , argument of sizeof, alignof, new, or typeid, name of type shall specified. can done type-id, syntactically declaration variable or function of type omits name of entity.


Comments

Post a Comment

Popular posts from this blog

apache - Remove .php and add trailing slash in url using htaccess not loading css -

i have add following code htaccess file removing .php extension , add trailing slash urls. worked fine reduced page loading speed , css code not loading @ all. pages ugly. please help rewriteengine on rewritebase / ## hide .php extension snippet # externally redirect /dir/foo.php /dir/foo rewritecond %{the_request} ^[a-z]{3,}\s([^.]+)\.php [nc] rewriterule ^ %1/ [r,l] # add trailing slash rewritecond %{request_filename} !-f rewritecond %{request_uri} !/$ rewriterule . %{request_uri}/ [l,r=301] # internally forward /dir/foo /dir/foo.php rewritecond %{request_filename} !-d rewritecond %{request_filename}.php -f rewriterule ^(.*?)/?$ $1.php [l] we can rewrite urls using .htaccess files. before writing in .htaccess files need verify kind of server using. can check server adding a <?php phpinfo(); ?> in php page. ensure mod_rewrite module enabled in apache server. can identified checking phpinfo included page. common methods used url rewriting follows ...
Read more

javascript - jQuery show full size image on click -

pretty self explanatory not workking . i want display full image when user click on image... yes know there tons of plugins but i want keep simple. any idea ? css : .full { display: none; width: 500px; height: 500px; margin-left: 100px; margin-top: -300px; position: fixed; background-color: #f00; z-index: 6; } .thumbnail { width: 50px; height: 50px; } html: <img class="thumbnail" src="http://4.bp.blogspot.com/-uhbdp2esxng/txneptvi92i/aaaaaaaaaky/upfqis7zto0/s1600/rihanna-wallpaper.jpg"> jquery: $(document).ready(function() { $('.thumbnail').on('click', function() { var img = $('<img />',{src:this.src,'class':'full'}); $('.full').html(img).show(); console.log('done!'); }); }); try looking how jquery works. $(document).ready(function() { $('.thumbnail').on('click', function(...
Read more