[fpc-pascal] Syserrormessage, parameter data type

[Sven Barth]

Am 06.10.2014 17:55 schrieb "Jürgen Hestermann" <juergen.hestermann at gmx.de>:
>
> Am 2014-10-06 um 07:55 schrieb Sven Barth:
>
> > On 06.10.2014 07:20, Jürgen Hestermann wrote:
> >>
> >> Am 2014-10-05 um 20:21 schrieb Sven Barth:
> >>> Please note that GetLastError is Windows-specific. The cross platform
> >>> function in SysUtils is called GetLastOSError which does return
Integer.
> >> And why does a function SysErrorMessage exist that expects an INTEGER
> >> and handes this over to FormatMessage which expects a DWORD?
> >
> > SysErrorMessage is the cross platform function while FormatMessage
> > is the Windows specific implementation so the types returned/used
> > by these two functions are already compatible.
>
> This is incorrect.
> SysErrorMessage expects an INTEGER while FORMATMESSAGEA is
> declared to use a DWORD parameter (see code snippets at the bottom).

I was a bit unclear here: I talked about the return type of GetLastOSError
and the parameter of SysErrorMessage.

>
>
> > GetLastOSError merely uses GetLastError on Windows (on Linux it
> > is errno for example) and casts its DWORD result to Integer.
>
> Again incorrect. GetLastOSError gives back an Integer and
> the DWORD coming from GetLastError it directly assigned to
> this integer-type Result. There is no type casting (see below).

There is nevertheless an implicit typecast performed by the compiler even
if in the end it's just a "mov" instruction (or something along that line).

Regards,
Sven
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