Symbols

Posted by ALB42 on 30. April 2017No Comments

Yesterday I was at the Amiga and retro computer meeting here in Berlin, always nice to be there and talk to the people. ChainQ was also there so we worked a little bit on this strange WBStartup problem on MorphOS. As some already mentioned in the comments to MUIMapparium, it is not possible to start fpc compiled programs at MorphOS via an Icon. The programs just do not start directly freeze, the reason is simple, when starting via Icon the WBStartup Message is sent to the application via an MsgPort at the Process structure. Freepascal waits for this Message, which never arrives. After some trying we found, that the needed structures and functions in fpc are in good shape so not the root of this problem. The problem appeared when ChainQ changed the startup code from a assembler one to a pure Pascal startup code. So my guess was that it somehow relates to the needed symbol inside the executable, which defines it as a MorphOS executeable __abox__. Of course I do not have much knowledge about it, just a wild guess. But it turns out that this was quite right. The first problem is that I used an older version of vlink, which seems to have a bug and removed this symbol (because never used). After an new compilation of vlink the __abox__ symbol is there but still it do not work. ChainQ knows a little bit more about this stuff and also knows whom to ask in the inner circle of MorphOS developer what could be the root of it. Some strange things I was able to see, the program I started stopped when starting via Icon. But via TaskManager you can see, two of them are started. An other thing with Snoopium you can check when the program does at the start. Especially the OpenLibrary function is interesting in this case. You can see how the program tries to open the ppc.library, which I learned now, is a sign that MorphOS thinks that this program is an PowerUp executable, which explains the odd behavior. In the end the solution was not so difficult, FreePascal did not set symbol type and symbol size as expected by MorphOS. (The size is important because the __abox__ symbol should point to a longword with value one) It appears FreePascal already have a function to care about such things, which only have to be activated for the MorphOS compiler. Finally it’s fixed again. Thanks for the help.

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