How do I retrieve an error string from WSAGetLastError()?

Question

I\'m porting some sockets code from Linux to Windows.

In Linux, I could use strerror() to convert an errno code into a human-readable string.

MS

Answer 1

A slightly simpler version of mxcl's answer, which removes the need for malloc/free and the risks implicit therein, and which handles the case where no message text is available (since Microsoft doesn't document what happens then):

int
   err;

char
   msgbuf [256];   // for a message up to 255 bytes.


msgbuf [0] = '\0';    // Microsoft doesn't guarantee this on man page.

err = WSAGetLastError ();

FormatMessage (FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,   // flags
               NULL,                // lpsource
               err,                 // message id
               MAKELANGID (LANG_NEUTRAL, SUBLANG_DEFAULT),    // languageid
               msgbuf,              // output buffer
               sizeof (msgbuf),     // size of msgbuf, bytes
               NULL);               // va_list of arguments

if (! *msgbuf)
   sprintf (msgbuf, "%d", err);  // provide error # if no string available