在Mac OS X中进行make时出现错误的未知类型名称'constexpr'

Question

当我使用scons编写一些程序时，会发生类似的错误，

错误：未知类型名称'constexpr'

错误：预期的不合格ID

我已经安装了xcode和xquartz最新版本。这是我的Mac clang版本

Apple LLVM版本8.1.0（clang-802.0.42）目标：x86_64-apple-darwin16.6.0线程模型：posix InstalledDir：/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

而且，我附上我的整个错误日志，以防万一。

/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:54:10: error: unknown type name 'constexpr'
static constexpr double     pi  = 3.1415;
       ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:54:20: error: expected unqualified-id
static constexpr double     pi  = 3.1415;
                 ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:55:10: error: unknown type name 'constexpr'
static constexpr double  twopi  = 2*pi;
       ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:55:20: error: expected unqualified-id
static constexpr double  twopi  = 2*pi;
                 ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:56:10: error: unknown type name 'constexpr'
static constexpr double halfpi  = pi/2;
       ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:56:20: error: expected unqualified-id
static constexpr double halfpi  = pi/2;
                 ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:57:10: error: unknown type name 'constexpr'
static constexpr double     pi2 = pi*pi;
       ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:57:20: error: expected unqualified-id
static constexpr double     pi2 = pi*pi;
                 ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:62:10: error: unknown type name 'constexpr'
static constexpr double millimeter  = 1.;
       ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:62:20: error: expected unqualified-id
static constexpr double millimeter  = 1.;
                 ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:63:10: error: unknown type name 'constexpr'
static constexpr double millimeter2 = millimeter*millimeter;
       ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:63:20: error: expected unqualified-id
static constexpr double millimeter2 = millimeter*millimeter;
                 ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:64:10: error: unknown type name 'constexpr'
static constexpr double millimeter3 = millimeter*millimeter*millimeter;
       ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:64:20: error: expected unqualified-id
static constexpr double millimeter3 = millimeter*millimeter*millimeter;
                 ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:66:10: error: unknown type name 'constexpr'
static constexpr double centimeter  = 10.*millimeter;
       ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:66:20: error: expected unqualified-id
static constexpr double centimeter  = 10.*millimeter;
                 ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:67:10: error: unknown type name 'constexpr'
static constexpr double centimeter2 = centimeter*centimeter;
       ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:67:20: error: expected unqualified-id
static constexpr double centimeter2 = centimeter*centimeter;
                 ^
/Users/jeon.hk/Documents/geant4/geant4.10.3-install/bin/../include/Geant4/CLHEP/Units/SystemOfUnits.h:68:10: error: unknown type name 'constexpr'
static constexpr double centimeter3 = centimeter*centimeter*centimeter;
       ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
scons: *** [build/macosx64/rat.o] Error 1 
scons: building terminated because of errors.

我真的很感谢您的任何评论。

Answer 1

正确的答案是编译启用c ++ 11支持（针对clang -std=c++11）以便识别constexpr关键字。