Hi,

I'm trying to assing dynamic array variables to a record type on the heap and handing that record over to the caller:

type
TCompoundInfo = record
		Id: hid_t;
		Name: string;
		TotalSize: longword;
		ElementNames: array of PChar;
		ElementSizes: array of longword;
		ElementTypes: HidTArray;
		ElementOffsets: array of longword;
	end;
PTableInfo = ^TTableInfo;
TTableInfo = TCompoundInfo;
  TBaseCompoundDescriptor = class
  private
    fItemName: string;
    fTotalTypeSize: longword;
    fFieldCount: integer;
    fFieldNames: array of PChar;
    fFieldSizes: array of longword;
    fFieldOffsets: array of longword;
    fFieldTypes: HidtArray;

TTableDescriptor = class(TBaseCompoundDescriptor)
...
...

constructor TTableDescriptor.create;
begin
  inherited create;
  GetMem(fInfo, sizeof(TTableInfo));
...
function TTableDescriptor.GetInfo: PTableInfo;
begin
  with fInfo^ do begin
    Name := fItemName;
    TotalSize := fTotalTypeSize;
    ElementNames := fFieldNames;

the last line trying to assign a (already sized and holding information) dynamic array to a similar variable fails:

Program received signal SIGSEGV, Segmentation fault. 0x8051eb5 in fpc_dynarray_decr_ref ()
(gdb) bt
#0 0x8051eb5 in fpc_dynarray_decr_ref ()
#1 0x80a2b26 in TTABLEDESCRIPTOR__GETINFO (this=0x283981e8) at CompoundTypes.pas:398 #2 0x80624e3 in TDS_HDF__INIT (C=0x80a8fc4, this=0x283c8028) at DS_HDF.pp:210 #3 0x8064fd1 in TDATACONVERTER__CONVERT (this=0x283b0248) at DataConverter.pp:191 #4 0x8049425 in main () at DC.pas:156

The ref guide says when assigning one dyn-array to another variable of the same type, this is done by reference and those arrays are ref-counted.

Why does it fail?

I tried using SetLength on the target var first, same error.

TIA,
Marc

Marc Santhoff wrote

constructor TTableDescriptor.create; begin inherited create; GetMem(fInfo, sizeof(TTableInfo));

Getmem allocates memory, but does not perform any initialisation. Use new() for record types containing fields that must be initialised (such as all reference counted types).

Joans

That does work. :)

So the caller has to use Dispose() instead of FreeMem() or will the work the same?

Thanks,
Marc

It's the same deal: freemem frees record's memory but does not finalise its contents, so you get memory leaks. Use dispose.

Jonas