-O1 / 2/3与-std = c ++ 1y / 11/98 - 如果< cmath>是包含我得到错误：'_hypot'没有在此范围中声明 [英] -O1/2/3 with -std=c++1y/11/98 - If <cmath> is included i'm getting error: '_hypot' was not declared in this scope

问题描述

我刚刚更新MinGW使用 mingw-get-setup ，我无法建立包含< cmath> code> -std = c ++ 1y 时，使用大于 -O0 （我也试过 c ++ 11 和 c ++ 98 ）我得到这样的错误： / p>

I've just updated MinGW using mingw-get-setup and i'm unable to build anyting that contains <cmath> header if I use anything larger than -O0 with -std=c++1y. (I also tried c++11 and c++98) I'm getting errors like this one:

g++.exe -pedantic-errors -pedantic -Wextra -Wall -std=c++1y -O3  -c Z:\Projects\C++\L6\src\events.cpp -o obj\src\events.o
In file included from z:\lander\mingw\lib\gcc\mingw32\4.8.1\include\c++\cmath:44:0,
                 from Z:\Projects\C++\L6\src\utils.h:4,
                 from Z:\Projects\C++\L6\src\events.cpp:10:
z:\lander\mingw\include\math.h: In function 'float hypotf(float, float)':
z:\lander\mingw\include\math.h:635:30: error: '_hypot' was not declared in this scope
 { return (float)(_hypot (x, y)); }

我的身边有问题吗？

或mingw repo的版本bugged？

Is something wrong on my side?
Or version at mingw repo is bugged? And if so, is there any quick fix for this header?

推荐答案

为了避免任何进一步的猜测，以及严重的错误建议，如使用 #if 0 ，让我从MinGW项目贡献者的角度给出权威的答案。

To avoid any further speculation, and downright bad suggestions such as using #if 0, let me give an authoritative answer, from the perspective of a MinGW project contributor.

是， include / math.h 的MinGW.org实现确实在其内联实现中有一个错误 hypotf（float，float）;编译C ++时会触发错误，包括受影响的标题（因为它包含 cmath ），和任何编译器选项，指定要定义的code> __ STRICT_ANSI __ （如 -std = c ... OP）。合适的解决方案是不封闭 math.h 文件的一部分， #if 0 或其他，但是要更正 hypotf（float，float）的破坏的内联实现;只需从内联引用 _hypot（float，float）中删除​​假的前导下划线，其中的返回值强制转换为float返回类型就足够了。

Yes, the MinGW.org implementation of include/math.h does have a bug in its inline implementation of hypotf (float, float); the bug is triggered when compiling C++, with the affected header included (as it is when cmath is included), and any compiler option which causes __STRICT_ANSI__ to become defined is specified, (as is the case for those -std=c... options noted by the OP). The appropriate solution is not to occlude part of the math.h file, with #if 0 or otherwise, but to correct the broken inline implementation of hypotf (float, float); simply removing the spurious leading underscore from the inline reference to _hypot (float, float), where its return value is cast to the float return type should suffice.

或者，用 -std = gnu ... 替换 -std = c ... 在编译器选项应该绕过bug，并可能提供一个合适的解决方法。

Alternatively, substituting an equivalent -std=gnu... for -std=c... in the compiler options should circumvent the bug, and may offer a suitable workaround.

FWIW，我不完全满意MinGW.org的当前实现 hypotl（long double，long double） either;纠正这两个问题是我下一个版本的MinGW运行时打印列表，但ATM，我没有时间专心准备这个。

FWIW, I'm not entirely happy with MinGW.org's current implementation of hypotl (long double, long double) either; correcting both issues is on my punch list for the next release of the MinGW runtime, but ATM, I have little time to devote to preparing this.

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