c++ - g++ 4.7 bug with SFINAE + decltype? -

-

i have constructed following mcve illustrate issue i'm having g++ 4.7. uses sfinae via decltype() determine if functor type can called given argument type (specialized test if functor type can called no arguments when argument type void).

#include <iostream> #include <utility>  template <typename f, typename a> class can_call_functor_impl { private:     typedef char yes[1];     typedef char no[2];      template <typename u>     static auto test(u *)         -> decltype(void(std::declval<u const &>()(std::declval<a &>())),                     std::declval<yes &>());      template <typename>     static no & test(...);  public:     static constexpr bool value = sizeof(test<f>(0)) == sizeof(yes); };  template <typename f> class can_call_functor_impl<f, void> { private:     typedef char yes[1];     typedef char no[2];      template <typename u>     static auto test(u *)         -> decltype(void(std::declval<u const &>()()),                     std::declval<yes &>());      template <typename>     static no & test(...);  public:     static constexpr bool value = sizeof(test<f>(0)) == sizeof(yes); };  template <typename f, typename a> class can_call_functor :     public std::integral_constant<bool, can_call_functor_impl<f, a>::value> {};  class int_functor { public:     void operator()(int) const; };  #define print_exp(e) (std::cout << #e " == " << (e) << std::endl)  int main(void) {     print_exp((can_call_functor<int_functor, int>::value));     print_exp((can_call_functor<int_functor, short>::value));     print_exp((can_call_functor<int_functor, void>::value));     print_exp((can_call_functor<int_functor, double>::value));     print_exp((can_call_functor<int_functor, int_functor>::value)); }

output on g++ (debian 4.7.2-5) 4.7.2:

(can_call_functor<int_functor, int>::value) == 1 (can_call_functor<int_functor, short>::value) == 1 (can_call_functor<int_functor, void>::value) == 1 (can_call_functor<int_functor, double>::value) == 1 (can_call_functor<int_functor, int_functor>::value) == 1

this output troubling, expect third , fifth lines have result of 0, , indeed later g++ , clang in agreement should case.

it appears g++ 4.7 evaluates can_call_functor<int_functor, t>::value true t can come with.

i suspect g++ bug specific 4.7, can't find evidence of (these kinds of problems being particularly difficult search on bug trackers), i'm looking definitive answer:

is g++ 4.7 bug, , if there workaround? if it's not bug in g++ bug in code?

is g++ 4.7 bug?

it appears be

on 4.9.1 produced

(can_call_functor<int_functor, int>::value) == 1 (can_call_functor<int_functor, short>::value) == 1 (can_call_functor<int_functor, void>::value) == 0 (can_call_functor<int_functor, double>::value) == 1 (can_call_functor<int_functor, int_functor>::value) == 0

but can't find evidence of (these kinds of problems being particularly difficult search on bug trackers)

this 1 might bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53788

and if there workaround?

ummm....

i cannot think one

move @ least 4.8? have several gcc installed side-by-side


Comments

Post a Comment

Popular posts from this blog

python - mat is not a numerical tuple : openCV error -

-
i have write down code showing error ma not getting it: please help: showing mat not numerical tuple: import cv import cv2 capture = cv2.videocapture("j.3gp") while(1): _, frame1 = capture.read() grayimage1 = cv2.cvtcolor(frame1, cv2.color_bgr2gray) _, frame2 = capture.read() grayimage2 = cv2.cvtcolor(frame2, cv2.color_bgr2gray) differenceimage = cv2.absdiff(grayimage1,grayimage2) thresholdimage = cv2.threshold(differenceimage,25,255,cv2.thresh_binary) cv2.imshow("difference image", differenceimage) cv2.imshow("threshold image", thresholdimage) cv2.imshow("image", frame1) k = cv2.waitkey(30) & 0xff error arising : ----------------------------------------------------------------------------------------- traceback (most recent call last): file "desk.py", line 15, in <module> cv2.imshow("threshold image", thresholdimage) typeerror: mat not numerical tuple
Read more

c# - MSAA finds controls UI Automation doesn't -

-
i'm working on automating windows application. i'm using teststack white framework. i've hit problem. program has 'window' object cannot see inside of. white shows no controls inside of it. inspect.exe shows no controls inside of either when running in ui automation mode. if switch inspect msaa see controls inside fine. there anyway me use msaa c# handle on these controls? if can identify msaa functions need, can use p/invoke call them c#. here's example article doing msaa: http://www.codeproject.com/articles/38906/ui-automation-using-microsoft-active-accessibility also, pinvoke.net can used identify iaccessible (msaa) functions: http://www.pinvoke.net/search.aspx?search=iaccessible&namespace=[all] here's answer along lines: msaa com-based? finally, alternative p/invoke, might able use tlbimp.exe create wrapper assembly oleacc.dll, , access msaa functions through it. i'm not sure if works msaa, it's worth try. as e
Read more

wordpress - .htaccess: RewriteRule: bad flag delimiters -

-
pulling hair out on one. have following .htaccess file custom redirects in addition wordpress's default settings. when tested on local wamp server worked fine after moving production i'm not getting rewriterule: bad flag delimiters error in server log , after while site goes down internal server error any appreciated. in advance! <ifmodule mod_rewrite.c> rewriteengine on rewritebase / rewriterule ^rockford_weddings___welcome\.html$ /wedding/ [r=301,l] rewriterule ^blog/?$ /journal/ [r=301,l] rewriterule ^blog/(.*)$ /$1 [r=301,l] rewriterule ^portraitinvestment/?$ /portraitinvestment\.pdf [r=301,l] rewriterule ^weddinginvestment/?$ /weddinginvestment\.pdf [r=301,l] rewriterule ^holidaycards2014/?$ /holidaycards2014\.pdf [r=301,l] </ifmodule> # begin wordpress <ifmodule mod_rewrite.c> rewriteengine on rewritebase / rewriterule ^index\.php$ - [l] rewritecond %{request_filename} !-f rewritecond %{request_filename} !-d rewriterule . /index.php [l] </
Read more