[Gambas-bugtracker] Bug #2534: Libc mmap() call always returns -1

[bugtracker at gambaswiki.org]

http://gambaswiki.org/bugtracker/edit?object=BUG.2534&from=L21haW4-

Comment #8 by Brian G:

Here is a summary of what I am using that seems to work well.

using pointers

Extern mmap(MapPoint As Pointer, MapLength As Integer, prot As Integer, flags As Integer, fd As Integer, offset As Integer) As Pointer In "libc:6"
Extern munmap(MapPoint As Pointer, MapLength As Integer) As Integer In "libc:6"
Extern shm_open(name As String, oflag As Integer, mode As Integer) As Integer In "librt:1"
Extern shm_unlink(name As String) As Integer In "librt:1"
Extern ftruncate(FileHandle As Integer, length As Integer) As Integer In "libc:6"

Static Private MemoryStorage As Pointer = Null                 ' actual storage address
Static Public NamedMemHandle As Integer = -1                       ' Handle of the named memory area

 NamedMemHandle = shm_open(MemName, O_CREAT Or O_RDWR Or O_EXCL, &O666) ' return an error if its already there
  If NamedMemHandle = -1 Then
    NamedMemHandle = shm_open(MemName, O_RDWR, &O666)
    If NamedMemHandle = -1 Then
      Error.Raise("Unable to open Named Shared Memory" & MemName & " " & Str(System.error) & " " & String@(strerror(System.error)))
      Return False
    Endif
  else
     If ftruncate(NamedMemHandle, MemSize + SharedMemoryControlHeader) = -1 Then
      Error "Unable to create the storage area for variables" & MemName & " " & Str(System.error) & " " & String@(strerror(System.error))
      rClose(NamedMemCollectionHandle)
      rClose(NamedMemHandle)
      shm_unlink(MemName)
      shm_unlink(ColName)
      Error.Raise("Unable to create the storage area for variables" & MemName & " " & Str(System.error) & " " & String@(strerror(System.error)))
    Endif
  Endif

'my interface supports named and unnammed memory
 If NamedMemHandle = -1 Then
      MemoryStorage = mmap(Null, BlockSize, (PROT_READ Or PROT_WRITE), (MAP_SHARED Or MAP_ANONYMOUS), NamedMemHandle, 0) 'Or MAP_ANONYMOUS
 Else
      MemoryStorage = mmap(Null, BlockSize, (PROT_READ Or PROT_WRITE), MAP_SHARED, NamedMemHandle, 0) 'Or MAP_ANONYMOUS
 Endif


Hope this helps!