[zeromq-dev] zmq_version

[Steven McCoy]

2010/1/27 Martin Sustrik <sustrik at 250bpm.com>

> Peter,
>
> > BTW, don't forget to add a function which returns the version of the
> > ZMQ library. That gives the bindings the chance to check whether they
> > are using the right version. At least for the Common Lisp bindings
> > this is important, because no code is compiled against the header
> > files. If the ZMQ API changes, this can result in error messages which
> > are hard to understand.
>
> Yes, this have been on TODO list for quite a long time already.
>
> Any suggestions about the format? Something like this?
>
> const char *version = zmq_version ();
> // version == "2.0-beta3"
>
>
For the C++ Google Protocol buffers has a pretty neat method of version
checking, just one macro GOOGLE_PROTOBUF_VERIFY_VERSION and it does all the
work for you.  A string or set of numbers is not so useful without a defined
means of checking for compatibility.

GLib and presumably a lot of the Gtk projects use a version triplet with
basic macro checker.

if (!GLIB_CHECK_VERSION (1, 2, 0))
    g_error ("GLib version 1.2.0 or above is needed");

http://library.gnome.org/devel/glib/stable/glib-Version-Information.html

Here are the relevant pieces inside protobufs,

// The current version, represented as a single integer to make comparison
// easier:  major * 10^6 + minor * 10^3 + micro
#define GOOGLE_PROTOBUF_VERSION 2001000

// The minimum library version which works with the current version of the
// headers.
#define GOOGLE_PROTOBUF_MIN_LIBRARY_VERSION 2001000

// The minimum header version which works with the current version of
// the library.  This constant should only be used by protoc's C++ code
// generator.
static const int kMinHeaderVersionForLibrary = 2001000;

// Verifies that the headers and libraries are compatible.  Use the macro
// below to call this.
void LIBPROTOBUF_EXPORT VerifyVersion(int headerVersion, int
minLibraryVersion,
                                      const char* filename);

// Converts a numeric version number to a string.
string LIBPROTOBUF_EXPORT VersionString(int version);

#define GOOGLE_PROTOBUF_VERIFY_VERSION                                    \
  ::google::protobuf::internal::VerifyVersion(                            \
    GOOGLE_PROTOBUF_VERSION, GOOGLE_PROTOBUF_MIN_LIBRARY_VERSION,         \
    __FILE__)

void VerifyVersion(int headerVersion,
                   int minLibraryVersion,
                   const char* filename) {
  if (GOOGLE_PROTOBUF_VERSION < minLibraryVersion) {
    // Library is too old for headers.
    GOOGLE_LOG(FATAL)
      << "This program requires version " <<
VersionString(minLibraryVersion)
      << " of the Protocol Buffer runtime library, but the installed version
"
         "is " << VersionString(GOOGLE_PROTOBUF_VERSION) << ".  Please
update "
         "your library.  If you compiled the program yourself, make sure
that "
         "your headers are from the same version of Protocol Buffers as your
"
         "link-time library.  (Version verification failed in \""
      << filename << "\".)";
  }
  if (headerVersion < kMinHeaderVersionForLibrary) {
    // Headers are too old for library.
    GOOGLE_LOG(FATAL)
      << "This program was compiled against version "
      << VersionString(headerVersion) << " of the Protocol Buffer runtime "
         "library, which is not compatible with the installed version ("
      << VersionString(GOOGLE_PROTOBUF_VERSION) <<  ").  Contact the program
"
         "author for an update.  If you compiled the program yourself, make
"
         "sure that your headers are from the same version of Protocol
Buffers "
         "as your link-time library.  (Version verification failed in \""
      << filename << "\".)";
  }
}

string VersionString(int version) {
  int major = version / 1000000;
  int minor = (version / 1000) % 1000;
  int micro = version % 1000;

  return strings::Substitute("$0.$1.$2", major, minor, micro);
}

-- 
Steve-o
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