接続数

COUNTER367101FROM 2012/5/16

MISRA-C diary(C言語日誌)

MISRA-C >> Article details

2014/06/14

C++N3242, 2011 (55) 7.1.5 The constexpr specifier

Tweet ThisSend to Facebook | by kaizen
// 1 filename:cpp2011-7-1-5.cpp
// ver 0.1 June.12, 2014
//
// 2 original examples and/or notes:
// (c) ISO/IEC JTC1 SC22 WG21 N3242, April 12, 2011
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
// > 7 Declarations 7.1 Specifiers 7.1.5 The constexpr specifier
//
// 3 compile and output mechanism:
// (c) Dr. OGAWA Kiyoshi, kaizen at gifu-u.ac.jp,
//
// 4 compile errors and/or warnings:
// 4.1(c) Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
// Target: x86_64-apple-darwin13.2.0,  Thread model: posix
// Command/Options: c++ -std=c++11 -stdlib=libc++ -Wall cpp2011-7-1-5.cpp 
// (c) LLVM 2003-2009 University of Illinois at Urbana-Champaign.

// 4.2. g++-4.9 (GCC) 4.9.0 20131229 (experimental)
// Copyright (C) 2013 Free Software Foundation, Inc.
// This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// http://gcc.gnu.org/onlinedocs/gcc/Standards.html
// Command/Options: g++-4.9  -std=c++11  -Wall cpp2011-7-1-5.cpp 
// g++-4.9: error: unrecognized command line option '-stdlib=libc++'
// Configuration:brew install gcc49
//
// 4.3. Visual Studio Express 2013, 
// (c) Microsoft http://www.visualstudio.com/
// SPEC:
// Windows 7, .NET Framework
// (c) VMware, Inc.
// VMWare fusion 6
//
// 5. Hardware:  MacBook Pro, 
//(c) Intel http://ark.intel.com/products/37006/
//Core 2 Duo 2.53GHz, 8GB, 1067MHz DDR3
//
// 6. Special Thanks: Upper organizatios and 
// ITSCJ/IPSJ http://www.itscj.ipsj.or.jp/itscj_english/index.html
// Renesas Electronics Corporation.http://www.renesas.com/
// NPO SESSAME project, http://www.sessame.jp/workinggroup/WorkingGroup3/
// Toyo Corporation, http://www.toyo.co.jp/English/
// Japan Standard Association, http://bit.ly/1lzykg1
// NPO TOPPERS project, https://www.toppers.jp/asp-d-download.html
// Daido Universcity, http://www.daido-it.ac.jp/gakubugakka/computer/index.html
// WITZ Co.Ltd., http://www.witz-inc.co.jp/products/solution/solution.html
// SevenWise.co., http://www.7ws.co.jp/index.html
// TOYOTA Motor Corporation, http://toyota.jp/
// IT planning Inc., http://www.itpl.co.jp/en/index.html
// DENSO Corporation, http://www.globaldenso.com/en/
// Aisin Seiki co. Ltd., http://www.aisin.com/
// Spancion Inc., http://www.spansion.com/
// Yazaki Corporation, http://www.yazaki-group.com/global/
// Pananosic Corporation, http://www.panasonic.net/
// SWEST: Summer Workshop on Embedded System Technologies , http://swest.toppers.jp
// CEST: Consortium for Embedded System Technology, http://www.ertl.jp/CEST/
// JUSE: Union of Japanese Scientists and Engineers, http://www.juse.or.jp/e/
// OSC:Open Source Conference, http://www.ospn.jp/

#include <iostream>
//#include <cstdlib>
//#include <string.h>
//#include <cstring>
//#include <type_traits>
//#include <cassert>
//#include <algorithm>
//#include <cmath>
//#include <complex>
using namespace std;
//
constexpr int square(int x); // OK: declaration
constexpr int bufsz = 1024; // OK: definition
//error: constexpr struct pixel { // error: pixel is a type
constexpr struct pixel_s {
int x;
int y;
constexpr pixel(int); // OK: declaration
};
constexpr pixel::pixel(int a)
: x(square(a)), y(square(a)) // OK: definition
{ }
//error: constexpr pixel small(2); // error: square not defined, so small(2)
// not constant (5.19) so constexpr not satisfied
constexpr int square(int x) { // OK: definition
return x * x;
}
constexpr pixel_s large(4); // OK: square defined
//error: int next(constexpr int x) { // error: not for parameters
//return x + 1;
//}
//error: extern constexpr int memsz; // error: not a definition
//
constexpr int square2(int x){ return x * x; } // OK
constexpr long long_max(){ return 2147483647; } // OK
constexpr int abs(int x){ return x < 0 ? -x : x; } // OK
//error: constexpr void f(int x) { /* ... */ }// error: return type is void
//error: constexpr int prev(int x){ return --x; } // error: use of decrement
constexpr int g(int x, int n) { // error: body not just “return expr”
int r = 1;
while (--n > 0) r *= x;
return r;
}
//
struct Length {
explicit constexpr Length(int i = 0) : val(i) { }
private:
int val;
};
//
constexpr int f(void *) { return 0; }
constexpr int f(...) { return 1; }
constexpr int g1() { return f(0); } // calls f(void *)
constexpr int g2(int n) { return f(n); } // calls f(...) even for n == 0
constexpr int g3(int n) { return f(n*0); } // calls f(...)
namespace N {
constexpr int c = 5;
constexpr int h() { return c; }
}
constexpr int c = 0;
constexpr int g4() { return N::h(); } // value is 5, c is not looked up again after the substitution
//
constexpr int f(bool b){ return b ? throw 0 : 0; } // OK
//error: constexpr int f() { throw 0; } // ill-formed, no diagnostic required
struct B {
constexpr B(int x) : i(0) { } // x is unused
int i;
};
int global;
struct D : B {
//error: constexpr D() : B(global) { } // ill-formed, no diagnostic required
// lvalue-to-rvalue conversion on non-constant global
//
};
class debug_flag {
public:
explicit debug_flag(bool);
//error: constexpr bool is_on(); // error: debug_flag not
// literal type
private:
bool flag;
};
constexpr int bar(int x, int y) // OK
{ return x + y + x*y; }
// ...
//error: int bar(int x, int y) // error: redefinition of bar
//{ return x * 2 + 3 * y; }
//
struct pixel {
int x, y;
};
constexpr pixel_s ur = { 1294, 1024 };// OK
//error: constexpr pixel origin; // error: initializer missing
//
int main() {
cout << global << std::endl;
cout << "7 Declarations 7.1 Specifiers 7.1.5 The constexpr specifier" << std::endl;
}
// 1 error
// 1.1 LLVM c++ -std=c++11 -stdlib=libc++ -Wall cpp2011-7-1-5.cpp 
cpp2011-7-1-5.cpp:79:11: error: C++ requires a type specifier for all declarations
constexpr pixel(int); // OK: declaration
~~~~~~~~~ ^
cpp2011-7-1-5.cpp:81:20: error: C++ requires a type specifier for all declarations
constexpr pixel_s::pixel(int a)
~~~~~~~~~          ^
cpp2011-7-1-5.cpp:82:1: error: only constructors take base initializers
: x(square(a)), y(square(a)) // OK: definition
^
cpp2011-7-1-5.cpp:89:19: error: no matching constructor for initialization of 'const pixel_s'
constexpr pixel_s large(4); // OK: square defined
                  ^     ~
cpp2011-7-1-5.cpp:76:18: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from 'int' to 'const pixel_s' for 1st
      argument
constexpr struct pixel_s {
                 ^
cpp2011-7-1-5.cpp:76:18: note: candidate constructor (the implicit move constructor) not viable: no known conversion from 'int' to 'pixel_s' for 1st argument
constexpr struct pixel_s {
                 ^
cpp2011-7-1-5.cpp:76:18: note: candidate constructor (the implicit default constructor) not viable: requires 0 arguments, but 1 was provided
cpp2011-7-1-5.cpp:97:15: error: constexpr declaration of 'abs' follows non-constexpr declaration
constexpr int abs(int x){ return x < 0 ? -x : x; } // OK
              ^
/usr/include/stdlib.h:129:6: note: previous declaration is here
int      abs(int) __pure2;
         ^
cpp2011-7-1-5.cpp:101:5: warning: variable declaration in a constexpr function is a C++1y extension [-Wc++1y-extensions]
int r = 1;
    ^
cpp2011-7-1-5.cpp:102:1: error: statement not allowed in constexpr function
while (--n > 0) r *= x;
^
cpp2011-7-1-5.cpp:109:5: warning: private field 'val' is not used [-Wunused-private-field]
int val;
    ^
>2 warnings and 6 errors generated.
// 1.2 gcc:  g++-4.9 -std=c++11 -Wall cpp2011-7-1-5.cpp 
cpp2011-7-1-5.cpp:79:20: error: ISO C++ forbids declaration of 'pixel' with no type [-fpermissive]
 constexpr pixel(int); // OK: declaration
                    ^
cpp2011-7-1-5.cpp:80:1: error: 'constexpr' cannot be used for type declarations
 };
 ^
cpp2011-7-1-5.cpp:81:11: error: 'pixel' does not name a type
 constexpr pixel::pixel(int a)
           ^
cpp2011-7-1-5.cpp:89:26: error: no matching function for call to 'pixel_s::pixel_s(int)'
 constexpr pixel_s large(4); // OK: square defined
                          ^
cpp2011-7-1-5.cpp:89:26: note: candidates are:
cpp2011-7-1-5.cpp:76:18: note: pixel_s::pixel_s()
 constexpr struct pixel_s {
                  ^
cpp2011-7-1-5.cpp:76:18: note:   candidate expects 0 arguments, 1 provided
cpp2011-7-1-5.cpp:76:18: note: constexpr pixel_s::pixel_s(const pixel_s&)
cpp2011-7-1-5.cpp:76:18: note:   no known conversion for argument 1 from 'int' to 'const pixel_s&'
cpp2011-7-1-5.cpp:76:18: note: constexpr pixel_s::pixel_s(pixel_s&&)
cpp2011-7-1-5.cpp:76:18: note:   no known conversion for argument 1 from 'int' to 'pixel_s&&'
cpp2011-7-1-5.cpp: In function 'constexpr int g(int, int)':
cpp2011-7-1-5.cpp:104:1: error: body of constexpr function 'constexpr int g(int, int)' not a return-statement
 }
 ^


21:35 | Impressed! | Voted(0) | Comment(0)