'SerialStream‘没有命名类型

Question

我用的是Ubuntu 14.04。我想将libSerial用于像描述的这里那样的项目。我使用sudo apt-get install libserial-dev安装了这个库。

我写了一个小程序(嗯，其实不是一个程序)：

#include "SerialStream.h"
#include <iostream>

#define PORT "/dev/ttyUSB0"

SerialStream ardu;

using namespace std;
using namespace LibSerial;

但是编译器说：‘SerialStream’ does not name a type

有什么帮助吗？

编辑:在将SerialStream ardu放在命名空间行之后，问题就更奇怪了：

g++ main.cpp -o ArduCom
/tmp/ccNzzINg.o: In Funktion `main':
main.cpp:(.text+0x7a): not defined reference to `LibSerial::SerialStream::Open(std::string, std::_Ios_Openmode)'
main.cpp:(.text+0x12d): not defined reference to `LibSerial::SerialStream::SetBaudRate(LibSerial::SerialStreamBuf::BaudRateEnum)'
main.cpp:(.text+0x181): not defined reference to `LibSerial::SerialStream::SetCharSize(LibSerial::SerialStreamBuf::CharSizeEnum)'
main.cpp:(.text+0x1d5): not defined reference to `LibSerial::SerialStream::SetParity(LibSerial::SerialStreamBuf::ParityEnum)'
main.cpp:(.text+0x229): not defined reference to `LibSerial::SerialStream::SetNumOfStopBits(short)'
main.cpp:(.text+0x27d): not defined reference to `LibSerial::SerialStream::SetFlowControl(LibSerial::SerialStreamBuf::FlowControlEnum)'
/tmp/ccNzzINg.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[_ZTVN9LibSerial15SerialStreamBufE]+0x48): not defined reference to `LibSerial::SerialStreamBuf::showmanyc()'
/tmp/ccNzzINg.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[_ZTVN9LibSerial15SerialStreamBufE]+0x50): not defined reference to `LibSerial::SerialStreamBuf::xsgetn(char*, long)'
/tmp/ccNzzINg.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[_ZTVN9LibSerial15SerialStreamBufE]+0x58): not defined reference to `LibSerial::SerialStreamBuf::underflow()'
/tmp/ccNzzINg.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[_ZTVN9LibSerial15SerialStreamBufE]+0x68): not defined reference to `LibSerial::SerialStreamBuf::pbackfail(int)'
/tmp/ccNzzINg.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[_ZTVN9LibSerial15SerialStreamBufE]+0x70): not defined reference to `LibSerial::SerialStreamBuf::xsputn(char const*, long)'
/tmp/ccNzzINg.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[_ZTVN9LibSerial15SerialStreamBufE]+0x78): not defined reference to `LibSerial::SerialStreamBuf::overflow(int)'

Answer 1

首先，您从名称空间LibSerial中定义了一个类型为LibSerial的对象，但没有对它进行适当的限定：

#include "SerialStream.h"
#include <iostream>

#define PORT "/dev/ttyUSB0"

SerialStream ardu; // error this type is unqualified

using namespace std;
using namespace LibSerial;

有许多方法来限定类型。一种方法是将定义放在命名空间的使用声明之后，类型在以下文件中定义：

#include "SerialStream.h"
#include <iostream>

#define PORT "/dev/ttyUSB0"

using namespace std;
using namespace LibSerial;

// qualified by the compiler searching through the
// declared namespaces and finding it in `namespace LibSerial`.

SerialStream ardu; 

另一种方法是将typename显式地限定为属于特定的命名空间：

LibSerial::SerialStream ardu; // fully qualifies name

这样做后，您的第二个问题是编译器需要知道libserial库位于文件系统中的位置，以便能够链接到它。

假设您将库安装到默认位置，那么这可能就足够了：

g++ main.cpp -o ArduCom -lserial

否则，您可能必须指定库使用-L开关的位置：

g++ main.cpp -o ArduCom -Wl,-rpath,/path/to/library/folder -L/path/to/library/folder -lserial

libserial库是使用自动工具构建的，因此，如果您从源代码构建和安装它，它将提供链接说明作为安装过程的一部分。

这些说明有点像这样：

----------------------------------------------------------------------
Libraries have been installed in:
   /path/to/libserial/lib

If you ever happen to want to link against installed libraries
in a given directory, LIBDIR, you must either use libtool, and
specify the full pathname of the library, or use the '-LLIBDIR'
flag during linking and do at least one of the following:
   - add LIBDIR to the 'LD_LIBRARY_PATH' environment variable
     during execution
   - add LIBDIR to the 'LD_RUN_PATH' environment variable
     during linking
   - use the '-Wl,-rpath -Wl,LIBDIR' linker flag
   - have your system administrator add LIBDIR to '/etc/ld.so.conf'

See any operating system documentation about shared libraries for
more information, such as the ld(1) and ld.so(8) manual pages.
----------------------------------------------------------------------