我有一个对我来说看起来很奇怪的问题。我的代码是：
#include <string>
#include <chrono>
#include <thread>
#include <ncurses.h>
int main(int argc, char const *argv[])
{
const unsigned int refresh_time_miliseconds = 500;
const int exit_key1 = 'q';
const int exit_key2 = 'Q';
initscr(); // Start curses mode
cbreak();
nodelay(stdscr, TRUE); // getch is noblocking
noecho(); // don't echo keyboard input
curs_set(0); // make cursor invisible
printw("To quit hit the key '%c' or '%c'\n", exit_key1, exit_key2);
refresh(); // Print it on the screen
int row, col;
getyx(stdscr,row,col);
int counter = 0;
int ch = 0;
while(ch != exit_key1 || ch != exit_key1) {
mvprintw(row, col, "Counter: %d\n", counter++);
std::string data = "Example";
printw("Data vector: %s\n", data.c_str());
refresh();
ch = getch();
std::this_thread::sleep_for(std::chrono::milliseconds(
refresh_time_miliseconds));
}
endwin(); // End curses mode
return 0;
}
它只是启动 ncurses 并打印计数器值和示例文本，直到用户按下“q”或“Q”键。
我尝试用以下方法编译它：
clang++ -o monitor -std=c++11 -Wall monitor.cpp --verbose -lncursesclang -x c++ -o monitor -std=c++11 -Wall monitor.cpp --verbose -lncursesclang version 3.8.1-16 (tags/RELEASE_381/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.2.1
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1
Candidate multilib: .;@m64
Selected multilib: .;@m64
"/usr/lib/llvm-3.8/bin/clang" -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name monitor.cpp -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -v -dwarf-column-info -debugger-tuning=gdb -resource-dir /usr/lib/llvm-3.8/bin/../lib/clang/3.8.1 -internal-isystem /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../../include/c++/6.2.1 -internal-isystem /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../../include/x86_64-linux-gnu/c++/6.2.1 -internal-isystem /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../../include/x86_64-linux-gnu/c++/6.2.1 -internal-isystem /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../../include/c++/6.2.1/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-3.8/bin/../lib/clang/3.8.1/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -Wall -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /home/mike/REPOS/AGH_SO_Coffee/PROBLEM -ferror-limit 19 -fmessage-length 158 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/monitor-9488c0.o -x c++ monitor.cpp
clang -cc1 version 3.8.1 based upon LLVM 3.8.1 default target x86_64-pc-linux-gnu
ignoring nonexistent directory "/include"
ignoring duplicate directory "/usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../../include/x86_64-linux-gnu/c++/6.2.1"
#include "..." search starts here:
#include <...> search starts here:
/usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../../include/c++/6.2.1
/usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../../include/x86_64-linux-gnu/c++/6.2.1
/usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../../include/c++/6.2.1/backward
/usr/local/include
/usr/lib/llvm-3.8/bin/../lib/clang/3.8.1/include
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
"/usr/bin/ld" --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o monitor /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../x86_64-linux-gnu/crt1.o /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../x86_64-linux-gnu/crti.o /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/crtbegin.o -L/usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1 -L/usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../.. -L/usr/lib/llvm-3.8/bin/../lib -L/lib -L/usr/lib /tmp/monitor-9488c0.o -lncurses -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/crtend.o /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.1/../../../x86_64-linux-gnu/crtn.o
/tmp/monitor-9488c0.o: In function `main':
monitor.cpp:(.text+0x190): undefined reference to `std::allocator<char>::allocator()'
monitor.cpp:(.text+0x1a7): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&)'
monitor.cpp:(.text+0x1b5): undefined reference to `std::allocator<char>::~allocator()'
monitor.cpp:(.text+0x1be): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::c_str() const'
monitor.cpp:(.text+0x237): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()'
monitor.cpp:(.text+0x24e): undefined reference to `std::allocator<char>::~allocator()'
monitor.cpp:(.text+0x265): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()'
/tmp/monitor-9488c0.o:(.eh_frame+0x13): undefined reference to `__gxx_personality_v0'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
我注意到，如果我注释掉所有对 std::string: 的引用：
std::string data = "Example";
printw("Data vector: %s\n", data.c_str());
然后两个编译命令都成功。
你知道我为什么会观察到这种行为吗？
患者：“当我这样做时，我的手臂很痛！”
医生：“不要这样做！”
clang 是一个 C 编译器。它不会自动链接 C++ 运行时库（为什么会这样？）
clang++ 是一个 C++ 编译器。
默认情况下，Clang 不链接标准 C++ 库（是的，需要多个库）。
clang -x c++cmake-lc++