[fpc-devel]Delphi incompatibility again!
Pavel V. Ozerski
pavel at insect.mail.iephb.ru
Mon Apr 2 14:40:29 CEST 2001
Again a Delphi incompatibility is found! At least with Delphi 3. Essence: the internals of longbool, wordbool and bytebool
types in FPC aren't the same as in Delphi 3. That causes serious problems by porting Delphi code with typecastings
like word(a_wordbool_variable), e.g. by calculating of index offsets in arrays!
A sample which demonstrates differences between FPC and Delphi 3:
writeln(longint(x),' ',word(y),' ',byte(z),' ',byte(w));
1) sample is compiled by FPC:
1 1 1 1
2) sample is compiled by Delphi 3:
-1 65535 255 1
Cause (only essence, I did not search details in compiler source):
Delphi 3 sets ALL bits in variable to binary 1 if the variable value will be true and its type is
longbool, wordbool or even bytebool (unlike boolean).
Unlike Delphi, FPC uses actually only one bit.
Pavel V. Ozerski | Inst. of Evolutionary Physiology & Biochemistry,
office +7 (812)552-6870(291)| Russian Academy of Sciences,
FAX +7 (812)552-3012 | Thorez pr. 44, St.Petersburg, 194223, Russia
home +7 (812)528-5576 | E-mail: pavel at insect.mail.iephb.ru
| pavel at insect.ief.spb.su
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