Calling external dll with array of pchar as parameter in XE - delphi

Question

I have a delphi project that works fine in delphi 6, but when I upgraded to XE it does not work.
I know it has to do with the new unicode type in delphi XE, I have tried changing the definition of the parameter from pchar to pansichar, ansichar but no succes so far. Can anyone see what i have done wrong?
My project calls a function in an third party dll that is defined like this:
type
PPChar = array of PChar;
{$EXTERNALSYM gsapi_init_with_args}
function gsapi_init_with_args(pinstance:Pgs_main_instance;argc:integer;argv:PPChar):integer; stdcall;
Implementation
{$EXTERNALSYM gsapi_init_with_args}
function gsapi_init_with_args; stdcall; external gsdll32 name 'gsapi_init_with_args';
And here is how I call the function.
procedure PSPDF(input : string; output:string);
var
code:integer;
instance:Pointer;
argv:array of PAnsiChar;
begin
new(instance);
setlength(argv,10);
code:=gsapi_new_instance(#instance,nil);
if code<>0 then
begin
raise Exception.Create('Impossible to open an instance of ghostscript. Error code: '+IntToStr(code));
end;
try
argv[0] := PAnsiChar('ps2pdf');
argv[1] := PAnsiChar('-dNOPAUSE');
argv[2] := PAnsiChar('-dBATCH');
argv[3] := PAnsiChar('-dSAFER');
argv[4] := PAnsiChar('-sDEVICE=pdfwrite');
argv[5] := PAnsiChar(PAnsiString('-sOutputFile='+output));
argv[6] := PAnsiChar('-c');
argv[7] := PAnsiChar('.setpdfwrite');
argv[8] := PAnsiChar('-f');
argv[9] := PAnsiChar(PAnsiString(input));
gsapi_new_instance(instance, nil);
code := gsapi_init_with_args(instance,length(argv),#argv[0]);
if code<0 then
raise Exception.Create('ERROR: init_args: '+IntToStr(code));
gsapi_exit(instance);
gsapi_delete_instance(instance);
finally
end;
end;
I will very much appreciate if someone can help me out.
Mario.

Answer 1

Changing PChar to PAnsiChar is the correct thing to do, however array of ... is not safe to use in DLL function parameters and was the wrong thing to use even in your Delphi 6 project. After looking at the official Ghostscript documentation, try this instead, in both projects:
interface
type
PPAnsiChar = ^PAnsiChar;
{$NODEFINE PPAnsiChar}
function gsapi_new_instance(var pinstance: Pointer; caller_handle: Pointer): Integer; stdcall;
{$EXTERNALSYM gsapi_new_instance}
procedure gsapi_delete_instance(instance: Pointer); stdcall;
{$EXTERNALSYM gsapi_delete_instance}
function gsapi_init_with_args(instance: Pointer; argc: Integer; argv: PPAnsiChar): Integer; stdcall;
{$EXTERNALSYM gsapi_init_with_args}
function gsapi_exit(instance: Pointer): Integer; stdcall;
{$EXTERNALSYM gsapi_exit}
implementation
function gsapi_new_instance; external gsdll32 name 'gsapi_new_instance';
procedure gsapi_delete_instance; external gsdll32 name 'gsapi_delete_instance';
function gsapi_init_with_args; external gsdll32 name 'gsapi_init_with_args';
function gsapi_exit; external gsdll32 name 'gsapi_exit';
.
procedure PSPDF(input : AnsiString; output: AnsiString);
var
code:integer;
instance: Pointer;
argv: array of PAnsiChar;
begin
code := gsapi_new_instance(instance, nil);
if code < 0 then
raise Exception.Create('Impossible to open an instance of ghostscript. Error code: '+IntToStr(code));
try
SetLength(argv, 10);
argv[0] := PAnsiChar('ps2pdf');
argv[1] := PAnsiChar('-dNOPAUSE');
argv[2] := PAnsiChar('-dBATCH');
argv[3] := PAnsiChar('-dSAFER');
argv[4] := PAnsiChar('-sDEVICE=pdfwrite');
argv[5] := PAnsiChar('-sOutputFile='+output);
argv[6] := PAnsiChar('-c');
argv[7] := PAnsiChar('.setpdfwrite');
argv[8] := PAnsiChar('-f');
argv[9] := PAnsiChar(input);
code := gsapi_init_with_args(instance, Length(argv), #argv[0]);
if code < 0 then
raise Exception.Create('ERROR: init_args: '+IntToStr(code));
try
...
finally
gsapi_exit(instance);
end;
finally
gsapi_delete_instance(instance);
end;
end;
Update: here is a corrected version of the gsapi.pas unit that should work in both Delphi versions:
// Copyright (c) 2001-2002 Alessandro Briosi
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use, copy,
// modify, merge, publish, distribute, sublicense, and/or sell copies
// of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//
//
// This software was written by Alessandro Briosi with the
// assistance of Russell Lang, as an example of how the
// Ghostscript DLL may be used Delphi.
//
unit gsapi;
interface
uses
Windows;
// {$HPPEMIT '#include <iminst.h>'}
const
gsdll32 = 'gsdll32.dll';
STDIN_BUF_SIZE = 128;
{$EXTERNALSYM STDIN_BUF_SIZE}
STDOUT_BUF_SIZE = 128;
{$EXTERNALSYM STDOUT_BUF_SIZE}
STDERR_BUF_SIZE = 128;
{$EXTERNALSYM STDERR_BUF_SIZE}
DISPLAY_VERSION_MAJOR = 1;
{$EXTERNALSYM DISPLAY_VERSION_MAJOR}
DISPLAY_VERSION_MINOR = 0;
{$EXTERNALSYM DISPLAY_VERSION_MINOR}
//* Define the color space alternatives */
DISPLAY_COLORS_NATIVE = $01;
{$EXTERNALSYM DISPLAY_COLORS_NATIVE}
DISPLAY_COLORS_GRAY = $02;
{$EXTERNALSYM DISPLAY_COLORS_GRAY}
DISPLAY_COLORS_RGB = $04;
{$EXTERNALSYM DISPLAY_COLORS_RGB}
DISPLAY_COLORS_CMYK = $08;
{$EXTERNALSYM DISPLAY_COLORS_CMYK}
DISPLAY_COLORS_MASK = $000f;
{$EXTERNALSYM DISPLAY_COLORS_MASK}
//* Define whether alpha information, or an extra unused bytes is included */
//* DISPLAY_ALPHA_FIRST and DISPLAY_ALPHA_LAST are not implemented */
DISPLAY_ALPHA_NONE = $00;
{$EXTERNALSYM DISPLAY_ALPHA_NONE}
DISPLAY_ALPHA_FIRST = $10;
{$EXTERNALSYM DISPLAY_ALPHA_FIRST}
DISPLAY_ALPHA_LAST = $20;
{$EXTERNALSYM DISPLAY_ALPHA_LAST}
DISPLAY_UNUSED_FIRST = $40; //* e.g. Mac xRGB */
{$EXTERNALSYM DISPLAY_UNUSED_FIRST}
DISPLAY_UNUSED_LAST = $80; //* e.g. Windows BGRx */
{$EXTERNALSYM DISPLAY_UNUSED_LAST}
DISPLAY_ALPHA_MASK = $0070;
{$EXTERNALSYM DISPLAY_ALPHA_MASK}
// * Define the depth per component for DISPLAY_COLORS_GRAY,
// * DISPLAY_COLORS_RGB and DISPLAY_COLORS_CMYK,
// * or the depth per pixel for DISPLAY_COLORS_NATIVE
// * DISPLAY_DEPTH_2 and DISPLAY_DEPTH_12 have not been tested.
// *
DISPLAY_DEPTH_1 = $0100;
{$EXTERNALSYM DISPLAY_DEPTH_1}
DISPLAY_DEPTH_2 = $0200;
{$EXTERNALSYM DISPLAY_DEPTH_2}
DISPLAY_DEPTH_4 = $0400;
{$EXTERNALSYM DISPLAY_DEPTH_4}
DISPLAY_DEPTH_8 = $0800;
{$EXTERNALSYM DISPLAY_DEPTH_8}
DISPLAY_DEPTH_12 = $1000;
{$EXTERNALSYM DISPLAY_DEPTH_12}
DISPLAY_DEPTH_16 = $2000;
{$EXTERNALSYM DISPLAY_DEPTH_16}
//* unused (1<<14) */
//* unused (1<<15) */
DISPLAY_DEPTH_MASK = $ff00;
{$EXTERNALSYM DISPLAY_DEPTH_MASK}
// * Define whether Red/Cyan should come first,
// * or whether Blue/Black should come first
// */
DISPLAY_BIGENDIAN = $00000; //* Red/Cyan first */
{$EXTERNALSYM DISPLAY_BIGENDIAN}
DISPLAY_LITTLEENDIAN = $10000; //* Blue/Black first */
{$EXTERNALSYM DISPLAY_LITTLEENDIAN}
DISPLAY_ENDIAN_MASK = $00010000;
{$EXTERNALSYM DISPLAY_ENDIAN_MASK}
//* Define whether the raster starts at the top or bottom of the bitmap */
DISPLAY_TOPFIRST = $00000; //* Unix, Mac */
{$EXTERNALSYM DISPLAY_TOPFIRST}
DISPLAY_BOTTOMFIRST = $20000; //* Windows */
{$EXTERNALSYM DISPLAY_BOTTOMFIRST}
DISPLAY_FIRSTROW_MASK = $00020000;
{$EXTERNALSYM DISPLAY_FIRSTROW_MASK}
//* Define whether packing RGB in 16-bits should use 555
// * or 565 (extra bit for green)
// */
DISPLAY_NATIVE_555 = $00000;
{$EXTERNALSYM DISPLAY_NATIVE_555}
DISPLAY_NATIVE_565 = $40000;
{$EXTERNALSYM DISPLAY_NATIVE_565}
DISPLAY_555_MASK = $00040000;
{$EXTERNALSYM DISPLAY_555_MASK}
type
TGSAPIrevision = record
product: PAnsiChar;
copyright: PAnsiChar;
revision: Longint;
revisiondat: Longint;
end;
TStdioFunction = function(caller_handle: Pointer; buf: PAnsiChar; len: Integer): Integer; stdcall;
TPollFunction = function(caller_handle: Pointer): Integer; stdcall;
TDisplayEvent = function(handle: Pointer; device: Pointer): Integer; cdecl;
TDisplayPreResizeEvent = function(handle: Pointer; device: Pointer;
width: Integer; height: Integer; raster: Integer; format: UINT): Integer; cdecl;
TDisplayResizeEvent = function(handle: Pointer; device: Pointer;
width: Integer; height: Integer; raster: Integer; format: UINT; pimage: PAnsiChar): Integer; cdecl;
TDisplayPageEvent = function(handle: Pointer; device: Pointer; copies: Integer; flush: Integer): Integer; cdecl;
TDisplayUpdateEvent = function(handle: Pointer; device: Pointer; x: Integer; y: Integer; w: Integer; h: Integer): Integer; cdecl;
TDisplayMemAlloc = procedure(handle: Pointer; device: Pointer; size: ulong); cdecl;
TDisplayMemFree = function(handle: Pointer; device: Pointer; mem: Pointer): Integer; cdecl;
TDisplayCallback = record
size: Integer;
version_major: Integer;
version_minor: Integer;
// New device has been opened */
// This is the first event from this device. */
display_open: TDisplayEvent;
// Device is about to be closed. */
// Device will not be closed until this function returns. */
display_preclose: TDisplayEvent;
// Device has been closed. */
// This is the last event from this device. */
display_close: TDisplayEvent;
// Device is about to be resized. */
// Resize will only occur if this function returns 0. */
// raster is byte count of a row. */
display_presize: TDisplayPreResizeEvent;
// Device has been resized. */
// New pointer to raster returned in pimage */
display_size: TDisplayResizeEvent;
// flushpage */
display_sync: TDisplayEvent;
// showpage */
// If you want to pause on showpage, then don't return immediately */
display_page: TDisplayPageEvent;
// Notify the caller whenever a portion of the raster is updated. */
// This can be used for cooperative multitasking or for
// progressive update of the display.
// This function pointer may be set to NULL if not required.
//
display_update: TDisplayUpdateEvent;
// Allocate memory for bitmap */
// This is provided in case you need to create memory in a special
// way, e.g. shared. If this is NULL, the Ghostscript memory device
// allocates the bitmap. This will only called to allocate the
// image buffer. The first row will be placed at the address
// returned by display_memalloc.
//
display_memalloc: TDisplayMemAlloc;
// Free memory for bitmap */
// If this is NULL, the Ghostscript memory device will free the bitmap */
display_memfree: TDisplayMemFree;
end;
PPAnsiChar = ^PAnsiChar;
{$NODEFINE PPAnsiChar}
function gsapi_revision(var pr: TGSAPIrevision; len: Integer): Integer; stdcall;
{$EXTERNALSYM gsapi_revision}
function gsapi_new_instance(var pinstance: Pointer; caller_handle: Pointer): Integer; stdcall;
{$EXTERNALSYM gsapi_new_instance}
procedure gsapi_delete_instance(pinstance: Pointer); stdcall;
{$EXTERNALSYM gsapi_delete_instance}
function gsapi_set_stdio(pinstance: Pointer;
stdin_fn: TStdioFunction; stdout_fn: TStdioFunction;
stderr_fn: TStdioFunction): Integer; stdcall;
{$EXTERNALSYM gsapi_set_stdio}
function gsapi_set_poll(pinstance: Pointer; poll_fn: TPollFunction): Integer; stdcall;
{$EXTERNALSYM gsapi_set_poll}
function gsapi_set_display_callback(pinstance: Pointer; const callback: TDisplayCallback): Integer; stdcall;
{$EXTERNALSYM gsapi_set_display_callback}
function gsapi_init_with_args(pinstance: Pointer; argc: Integer; argv: PPAnsiChar): Integer; stdcall;
{$EXTERNALSYM gsapi_init_with_args}
function gsapi_run_string_begin(pinstance: Pointer; user_errors: Integer; var pexit_code: Integer): Integer; stdcall;
{$EXTERNALSYM gsapi_run_string_begin}
function gsapi_run_string_continue(pinstance: Pointer; str: PAnsiChar; len: Integer; user_errors: Integer; var pexit_code: Integer): Integer; stdcall;
{$EXTERNALSYM gsapi_run_string_continue}
function gsapi_run_string_end(pinstance: Pointer; user_errors: Integer; var pexit_code: Integer): Integer; stdcall;
{$EXTERNALSYM gsapi_run_string_end}
function gsapi_run_string_with_length(pinstance: Pointer; str: PAnsiChar; len: Integer; user_errors: Integer; var pexit_code: Integer): Integer; stdcall;
{$EXTERNALSYM gsapi_run_string_with_length}
function gsapi_run_string(pinstance: Pointer; str: PAnsiChar; user_errors: Integer; var pexit_code: Integer): Integer; stdcall;
{$EXTERNALSYM gsapi_run_string}
function gsapi_run_file(pinstance: Pointer; file_name: PAnsiChar; user_errors: Integer; var pexit_code: Integer): Integer; stdcall;
{$EXTERNALSYM gsapi_run_file}
function gsapi_exit(pinstance: Pointer): Integer; stdcall;
{$EXTERNALSYM gsapi_exit}
implementation
function gsapi_revision; external gsdll32 name 'gsapi_revision';
function gsapi_new_instance; external gsdll32 name 'gsapi_new_instance';
procedure gsapi_delete_instance; external gsdll32 name 'gsapi_delete_instance';
function gsapi_set_stdio; external gsdll32 name 'gsapi_set_stdio';
function gsapi_set_poll; external gsdll32 name 'gsapi_set_poll';
function gsapi_set_display_callback; external gsdll32 name 'gsapi_set_display_callback';
function gsapi_init_with_args; external gsdll32 name 'gsapi_init_with_args';
function gsapi_run_string_begin; external gsdll32 name 'gsapi_run_string_begin';
function gsapi_run_string_continue; external gsdll32 name 'gsapi_run_string_continue';
function gsapi_run_string_end; external gsdll32 name 'gsapi_run_string_end';
function gsapi_run_string_with_length; external gsdll32 name 'gsapi_run_string_with_length';
function gsapi_run_string; external gsdll32 name 'gsapi_run_string';
function gsapi_run_file; external gsdll32 name 'gsapi_run_file';
function gsapi_exit; external gsdll32 name 'gsapi_exit';
end.

Answer 2

The old Delphi 6 PChar is PAnsiChar on Unicode Delphi (2009+), so everything should work if you change all the PChar references to PAnsiChar.
(Including your Pgs_main_instance declaration, if any PChar is over there)
type
PPAnsiChar = array of PAnsiChar;
{$EXTERNALSYM gsapi_init_with_args}
function gsapi_init_with_args(pinstance: Pgs_main_instance;
argc: Integer; argv:PPAnsiChar): Integer; stdcall;
implementation
function gsapi_init_with_args(pinstance: Pgs_main_instance;
argc: Integer; argv:PPAnsiChar): Integer;
external gsdll32 name 'gsapi_init_with_args';
Calling code:
var
argv:PPAnsiChar;
instance: Pointer;
begin
new(instance); //how many bytes, this really doesn't make sense with a untyped pointer!
setlength(argv, 4);
argv[0] := PAnsiChar('ps2pdf');
argv[1] := PAnsiChar('-dNOPAUSE');
argv[2] := PAnsiChar('-dBATCH');
argv[3] := PAnsiChar('-dSAFER');
gsapi_init_with_args(instance, Length(argv), argv);
end;
To understand what's new in Unicode, I advise you to read the Delphi and Unicode white paper from Marco Cantù.