C++ 使用constexpr进行编译时字符串连接 #包括 #包括 constexpr std:：string appendStringC（std:：string s） { 返回s+“Constexpr func”； } std:：string appendString（std:：string s） { 返回s+“常规函数”； } int main（） { std:：string s1=“string 1”； std:：string s2=“string 2”； std:：cout

std:string:：operator+（）

不是一个

constepr

，实际上它通常是以一种非常动态的方式实现的，依赖于堆内存。您可以像这样附加静态字符串常量：

const_string_generation.cpp: In function ‘constexpr std::__cxx11::string appendStringC(std::__cxx11::string)’:
const_string_generation.cpp:4:23: error: invalid type for parameter 1 of constexpr function ‘constexpr std::__cxx11::string appendStringC(std::__cxx11::string)’
 constexpr std::string appendStringC(std::string s)
                       ^
In file included from /usr/include/c++/5.3.0/string:52:0,
                 from /usr/include/c++/5.3.0/bits/locale_classes.h:40,
                 from /usr/include/c++/5.3.0/bits/ios_base.h:41,
                 from /usr/include/c++/5.3.0/ios:42,
                 from /usr/include/c++/5.3.0/ostream:38,
                 from /usr/include/c++/5.3.0/iostream:39,
                 from const_string_generation.cpp:1:
/usr/include/c++/5.3.0/bits/basic_string.h:71:11: note: ‘std::__cxx11::basic_string<char>’ is not literal because:
     class basic_string
           ^
/usr/include/c++/5.3.0/bits/basic_string.h:71:11: note:   ‘std::__cxx11::basic_string<char>’ has a non-trivial destructor
const_string_generation.cpp:4:23: error: invalid return type ‘std::__cxx11::string {aka std::__cxx11::basic_string<char>}’ of constexpr function ‘constexpr std::__cxx11::string appendStringC(std::__cxx11::string)’
 constexpr std::string appendStringC(std::string s)

---

您不能这样做，因为

std:：string

通常在内部使用动态分配（不太

constepr

-友好）。但是，您可以通过将两个或多个字符串文本按顺序排列来连接它们。@Cheersandhth.-Alf是的，但我有很多长字符串需要在字符串的前面或后面连接。有点像转义码，因此手动放置和编辑它们中的每一个可能很快就会变得笨拙。您可以使用char sequence，一些ike@Jarod42太麻烦了，如果没有任何效果，我只会抛出一个hacky宏方法。

const_string_generation.cpp: In function ‘constexpr std::__cxx11::string appendStringC(std::__cxx11::string)’:
const_string_generation.cpp:4:23: error: invalid type for parameter 1 of constexpr function ‘constexpr std::__cxx11::string appendStringC(std::__cxx11::string)’
 constexpr std::string appendStringC(std::string s)
                       ^
In file included from /usr/include/c++/5.3.0/string:52:0,
                 from /usr/include/c++/5.3.0/bits/locale_classes.h:40,
                 from /usr/include/c++/5.3.0/bits/ios_base.h:41,
                 from /usr/include/c++/5.3.0/ios:42,
                 from /usr/include/c++/5.3.0/ostream:38,
                 from /usr/include/c++/5.3.0/iostream:39,
                 from const_string_generation.cpp:1:
/usr/include/c++/5.3.0/bits/basic_string.h:71:11: note: ‘std::__cxx11::basic_string<char>’ is not literal because:
     class basic_string
           ^
/usr/include/c++/5.3.0/bits/basic_string.h:71:11: note:   ‘std::__cxx11::basic_string<char>’ has a non-trivial destructor
const_string_generation.cpp:4:23: error: invalid return type ‘std::__cxx11::string {aka std::__cxx11::basic_string<char>}’ of constexpr function ‘constexpr std::__cxx11::string appendStringC(std::__cxx11::string)’
 constexpr std::string appendStringC(std::string s)

"append this string " " to this string"