Not a member of global namespace?

Question

I have the error:

error C2039: 'read' : is not a member of '`global namespace'' and error C2661: 'Calc::SymString::read' : no overloaded function takes 3 arguments from the line: if (::read(fd_sock, &size, 4) != 4)

This error and similar ones appear quite a lot in my code. Does anyone know what the problem could be? I am using Windows Visual Studio 2010 and I am migrating code from Unix. Thanks in advance!

Answer 1

read() is a UNIX function defined (in LINUX) in unistd.h - all the documentation I have read indicates it is not a standard C function. That may be why it is compiling in UNIX but not in Windows.

In UNIX read() takes a file descriptor, but the equivalent construct in Windows is a "handle".

Do you really need low level file descriptor I/O in your program? Can you use fread , which is a standard C function?

This Microsoft support article describes the types of file handles available in Windows:

There are multiple types of file handles that can be opened using 
the Win32 API and the C Run-time:

   Returned Type  File Creation API      API Set
   ---------------------------------------------
   HANDLE         CreateFile()           Win32
   HFILE          OpenFile()/_lcreat()   Win32
   int            _creat()/_open()       C Run-time
   FILE *         fopen()                C Run-time

Answer 2

Microsoft declares the Unix-style I/O functions in io.h .

Try including that header - you may get a bunch of warnings about using deprecated names (MS would prefer you use the name _read() ). If so, you may want to define the macro _POSIX_ which should quiet those warnings.