[fpc-pascal]More strangeness...

L D Blake ldblake at sympatico.ca
Thu Aug 28 23:03:05 CEST 2003

In reply to your message of August 28, 2003

> On Thu, 28 Aug 2003, L D Blake wrote:

>> Why is it that if I compile an FPC program with range checking turned on,
>> opening any HTML file in ie immediately causes "Error 201" from my FPC program?

> Ahem.
> A litlle bit more information may be in order here ?
> What kind of program is this ? What units does it use ? What function
> does it perform ? Is this a GUI program or a console app ?

Okey dokey...  I gave quite a bit of information in my other message about
these problems... XP1800/win2k/sp4/256mbram/tnt64 video, all stable on other
software... so, to add the new info..

It's a Gui app. No OOP, just plain pascal. Basically it's media player with
some special functions, such as a text editor for transcribing lyrics. From
FPC, it uses only mmsystem and windows, and of course it has it's own private
units. I'm compiling with delphi and gui support enabled at the top of each
unit and in the main program.

To restate what's going on... If I compile without range checking it will play
songs perfectly, and the text editor behaves normally so long as I don't open
any other window over it or let it fall into the screen saver. If it goes into
the background I sometimes (often, but not every time) lose the title bars
from the windows and re-draws occur at random locations on the screen making
the program appear to break in to pieces, this happens with any window or
dialog the program opens, including those built into windows. If I guess where
the buttons should be I can click them, even if I can't see them and the
images scattered on the screen have the menu context numbers on them instead
of the button text. Sometimes it will also grab bits of other windows and
displace them as well. If I compile it with range checking it errors off (code
201 at random addresses) every time I try to open a html file in IE. The IE
window will not open until I exit the application. It also errors off
unexpectedly (but not very often) giving Error 201 at seemingly random
addresses while running in background.   All though this, it will continue
playing music very nicely...

Also, keep in mind that so long as it's in the foreqround, none of these errors
occur. I've tortured it horribly and it runs error free so long as it never
gets covered by anything else.

I've been all over my own code with a fine tooth comb. I've tried declaring my
variables with win-api names (eg. dword instead of longword) and I've tried
using the native pascal type declarations and this seems to have little effect
on it. I've tried re-doing the windows dispatcher and the 4 winproc routines
(one for each main window) in several different ways, but this does not change
the errors. I've also tried commenting out blocks of code to see if the error
vanishes along with the function and, unless I render it unworkable, the
errors persist.

The FP IDE will not point me to a source code line when the errors occur
because, weirdly enough, I don't get the errors in debug mode.

I'm slowly becoming convinced that it's an error someplace in FP, perhaps
in the "Windows" unit ... perhaps a type declaration that doesn't match the
C equivalent or some other more fundimental problem. I've experimented with
lots of differing combinations of compiler switches (in fpc.cfg) and tried
several different compiler directives in the source code itself. All to no
avail. Depending on the use of range checking, I either get a scrambled
display or randomly occuring "Error 201" popups sometimes listing 20 or more

So far, I've been resisting tampering with the FPC distribution, because
frankly I would have no idea where to start looking for these kinds of
problems in all that source code.

I was a professional programmer some years back, worked with TP extensively
and liked it just fine on the DOS platform, but FP and windows has been a real
hassle.  I've never yet had a problem I can't find and fix... until now.

Needless to say, I'm rather frustrated and very near scrapping FP...

 L D Blake

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