Why is this C appeal to Pascal turning?

Question

I have this C code:

/*
  WARNING:  The order of this table must also match the order of a table
  located in AcquireResizeFilter() in "resize.c" otherwise the users filter
  will not match the actual filter that is setup.
*/
typedef enum
{
  UndefinedFilter,
  PointFilter,
  BoxFilter,
  TriangleFilter,
  HermiteFilter,
  HannFilter,
  HammingFilter,
  BlackmanFilter,
  GaussianFilter,
  QuadraticFilter,
  CubicFilter,
  CatromFilter,
  MitchellFilter,
  JincFilter,
  SincFilter,
  SincFastFilter,
  KaiserFilter,
  WelchFilter,
  ParzenFilter,
  BohmanFilter,
  BartlettFilter,
  LagrangeFilter,
  LanczosFilter,
  LanczosSharpFilter,
  Lanczos2Filter,
  Lanczos2SharpFilter,
  RobidouxFilter,
  RobidouxSharpFilter,
  CosineFilter,
  SplineFilter,
  LanczosRadiusFilter,
  CubicSplineFilter,
  SentinelFilter  /* a count of all the filters, not a real filter */
} FilterType;

and

WandExport MagickBooleanType MagickResizeImage(MagickWand *wand,
  const size_t columns,const size_t rows,const FilterType filter)

I convert it to Pascal as follows:

type
  FilterType =(
    UndefinedFilter,
    PointFilter,
    BoxFilter,
    TriangleFilter,
    HermiteFilter,
    HannFilter,
    HammingFilter,
    BlackmanFilter,
    GaussianFilter,
    QuadraticFilter,
    CubicFilter,
    CatromFilter,
    MitchellFilter,
    JincFilter,
    SincFilter,
    SincFastFilter,
    KaiserFilter,
    WelchFilter,
    ParzenFilter,
    BohmanFilter,
    BartlettFilter,
    LagrangeFilter,
    LanczosFilter,
    LanczosSharpFilter,
    Lanczos2Filter,
    Lanczos2SharpFilter,
    RobidouxFilter,
    RobidouxSharpFilter,
    CosineFilter,
    SplineFilter,
    LanczosRadiusFilter,
    CubicSplineFilter,
    SentinelFilter);  // a count of all the filters, not a real filter

and

function MagickResizeImage(wand: PMagickWand; const columns: size_t; rows: size_t; const filter: FilterType): MagickBooleanType; cdecl; external MagickWandDLL;

When I call MagickResizeImage(), I get an access violation :(

if i change const filter: FilterTypeto const filter: integer, it works.

Any idea what I'm doing wrong?

Answer 1

In C on Windows, the enumeration is inttherefore 4 bytes in size. In Delphi, the default is one byte or two bytes if there are more than 256, etc.

You need to make sure that your Delphi type is the same size as type C. For example, using the directive MINENUMSIZE.

{$MINENUMSIZE 4}

Put this before you define a numbered type.