Question

我正在使用g ++ 4.6.3。这是g ++ -v的输出。

g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-linux-gnu/4.6/lto-wrapper
Target: i686-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.6.3-1ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-  languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --enable-targets=all --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=i686-linux-gnu --host=i686-linux-gnu --target=i686-linux-gnu
Thread model: posix
gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5)

以下是我的代码示例：

#include "Word.h"
#include <string>
using namespace std;

pthread_mutex_t Word::_lock = PTHREAD_MUTEX_INITIALIZER;

Word::Word():
_occurrences(1)
{
    memset(_buf, 0, 25);
}

Word::Word(char *str):
_occurrences(1)
{
    memset(_buf, 0, 25);
    if (str != NULL)
    {
        strncpy(_buf, str, strlen(str));
    }
}

g ++ -c -ansi或g ++ -c -std = c ++ 98或g ++ -c -std = c ++ 03，这些选项都不能正确构建代码。我收到以下编译错误：

mriganka@ubuntu:~/WordCount$ make
g++ -c -g -ansi Word.cpp -o Word.o
Word.cpp: In constructor ‘Word::Word()’:
Word.cpp:10:21: error: ‘memset’ was not declared in this scope
Word.cpp: In constructor ‘Word::Word(char*)’:
Word.cpp:16:21: error: ‘memset’ was not declared in this scope
Word.cpp:19:34: error: ‘strlen’ was not declared in this scope
Word.cpp:19:35: error: ‘strncpy’ was not declared in this scope
Word.cpp: In member function ‘void Word::operator=(const Word&)’:
Word.cpp:37:42: error: ‘strlen’ was not declared in this scope
Word.cpp:37:43: error: ‘strncpy’ was not declared in this scope
Word.cpp: In copy constructor ‘Word::Word(const Word&)’:
Word.cpp:44:21: error: ‘memset’ was not declared in this scope
Word.cpp:45:52: error: ‘strlen’ was not declared in this scope
Word.cpp:45:53: error: ‘strncpy’ was not declared in this scope

所以基本上Ubuntu 12.04上的g ++ 4.6.3无法识别标准的c ++头文件。我并没有找到摆脱这种情况的方法。

第二个问题：

为了取得进步，我包括了＆lt; string.h中＆GT;而不是＆lt;串取代。但现在我面临着将错误与我的消息队列和pthread库函数联系起来的问题。

这是我得到的错误：

mriganka@ubuntu:~/WordCount$ make
g++ -c -g -ansi Word.cpp -o Word.o
g++ -lrt -I/usr/lib/i386-linux-gnu Word.o HashMap.o main.o -o word_count
main.o: In function `main':
/home/mriganka/WordCount/main.cpp:75: undefined reference to `pthread_create'
/home/mriganka/WordCount/main.cpp:90: undefined reference to `mq_open'
/home/mriganka/WordCount/main.cpp:93: undefined reference to `mq_getattr'
/home/mriganka/WordCount/main.cpp:113: undefined reference to `mq_send'
/home/mriganka/WordCount/main.cpp:123: undefined reference to `pthread_join'
/home/mriganka/WordCount/main.cpp:129: undefined reference to `mq_close'
/home/mriganka/WordCount/main.cpp:130: undefined reference to `mq_unlink'
main.o: In function `count_words(void*)':
/home/mriganka/WordCount/main.cpp:151: undefined reference to `mq_open'
/home/mriganka/WordCount/main.cpp:154: undefined reference to `mq_getattr'
/home/mriganka/WordCount/main.cpp:162: undefined reference to `mq_timedreceive'
collect2: ld returned 1 exit status

这是我的makefile：

CC=g++ 
CFLAGS=-c -g -ansi 
LDFLAGS=-lrt 
INC=-I/usr/lib/i386-linux-gnu 
SOURCES=Word.cpp HashMap.cpp main.cpp 
OBJECTS=$(SOURCES:.cpp=.o) EXECUTABLE=word_count

all: $(SOURCES) $(EXECUTABLE)

$(EXECUTABLE): $(OBJECTS) $(CC) $(LDFLAGS) $(INC) -pthread $(OBJECTS) -o $@

.cpp.o: $(CC) $(CFLAGS) $< -o $@

clean: rm -f *.o word_count

请帮我解决这两个问题。我无情地在网上搜索了这些问题的任何解决方案，但似乎没有人遇到过这些问题。

Answer 1

这些项目位于<string.h>（或<cstring>），而不是<string>。

对于第二个问题，您需要链接到相应的库中。对于pthread，将-pthread添加到编译器命令行。对于消息队列库，您需要一个-l选项来命名库，并且可能需要一个-L选项，让工具知道它的位置。

无法用g ++ 4.6.3构建我的c ++代码

1 个答案: