UNIX 'read' conflicting with Myclass:read()

Question

Hello!
I'm cretaing a class FileChannel, qith a method called read. This mehod has the prototype:
int read(Buffer& buffer, int offset =0);And the implementation is like this:
int FileChannel::read(Buffer& buf, int offset){
     ssize_t howmanyQ = read( this->fileDescriptor, (buf.data()+offset), (size_t)buf.capacity()-offset);
     return howmanyQ;
}The compiler throws me this error(GCC 4.1):
../FileChannel.cpp: In member function �virtual int raxIO::FileChannel::read(raxIO::Buffer&, int)�:
../FileChannel.cpp:29: error: pointer of type �void *� used in arithmetic
../FileChannel.cpp:29: error: no matching function for call to �raxIO::FileChannel::read(int&, void*, unsigned int)�
../FileChannel.cpp:27: note: candidates are: virtual int raxIO::FileChannel::read(raxIO::Buffer&, int)
../FileChannel.hpp:31: note: virtual int raxIO::FileChannel::read(raxIO::Buffer&, int, int)
../FileChannel.hpp:32: note: virtual int raxIO::FileChannel::read(void*, int)
make: *** [FileChannel.o] Error 1
The include files at the beginning of my .cpp file are:
#include "FileChannel.hpp"
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
How can I solve this? :S Hlp Please
Edited by: RaulHuertas on Apr 7, 2008 1:34 PM

Answer 1

You haven't shown all the declarations that would affect whether the code is correct, nor shown which line numbers apply to the portion of source code that you supplied, so I can't provide a detailed answer. But I can make these observations, assuming line 29 is this one ssize_t howmanyQ = read( this->fileDescriptor, (buf.data()+offset), (size_t)buf.capacity()-offset);line 29, �void *� used in arithmetic:
Apparently you have declared Buffer::data() to return void*, and are trying to add an offset to the return value. That operation is not valid. If p is pointer type, p+1 means adding sizeof(*p) bytes to the address that p points to. Since sizeof(void) has no meaning, the operation is not valid. Probably Buffer::data() should return a type like char* or unsigned char*, but I can't say without seeing the design for class Buffer.
Note: Some compilers allow using void* in pointer arithmetic as a non-standard extension. Such code violates the C++ language standard, and you should not write code that depends on such an extension.
line 29, no matching function:
The call to read in function FIleChannel::read will try to call one of the overloaded "read" functions declared in FileChannel, which is probably not what you intended. Fortunately, none of the FileChannel::read functions has a matching parameter list, so the call failed at compile time instead giving a bizarre result or crashing at run time.
- If you meant the system call "read", you have to qualify the name to show you mean the one at global scope. If that is the case, write the name as ::read.
- If you meant some other function, use its fully-qualified name.
- If you actually meant to call one of the other FileChannel::read functions, you have to supply a set of arguments that matches the parameter list of one of them.