2012/6/30 Sven Barth <pascaldra...@googlemail.com>: > Your explanation is very nice and mostly correct, but in case of external > cdecl functions in FPC the "varargs" modifier and a "array of const" > parameter imply the same C compatible parameter passing in the compiler. See > also here: > http://freepascal.org/docs-html/ref/refsu77.html#x180-19000014.9.17 > > The only difference is when calling the functions. E.g.: > > procedure a(args: array of const); cdecl; external; > procedure b; cdecl; varargs; external; > > begin > a([1, 'foo', somevar]); > b(1, 'foo', somevar); > end.
This means in my case I declared the external function correctly and only need to pass [nil] to make it a null terminated list? Because I tried this last night and looked at the generated assembler and if I for example call it with purple_prpl_got_user_status(@self, Pointer(AName), Pointer(AStatusID), [1,2,3,nil]); then it will generate the following code: 0162EF17 6a00 push $0x0 0162EF19 6a03 push $0x3 0162EF1B 6a02 push $0x2 0162EF1D 6a01 push $0x1 0162EF1F ff75f8 pushl -0x8(%ebp) 0162EF22 ff75fc pushl -0x4(%ebp) 0162EF25 8b45f4 mov -0xc(%ebp),%eax 0162EF28 50 push %eax 0162EF29 e8b20afaff call 0x15cf9e0 <purple_prpl_got_user_status@plt> so its just just pushing the contents of the list onto the stack as they are and If I pass [] there would be nothing pushed at all, so the right thing for me to do in this case would be to call it with purple_prpl_got_user_status(@self, Pointer(AName), Pointer(AStatusID), [nil]); 0162EF17 6a00 push $0x0 0162EF19 ff75f8 pushl -0x8(%ebp) 0162EF1C ff75fc pushl -0x4(%ebp) 0162EF1F 8b45f4 mov -0xc(%ebp),%eax 0162EF22 50 push %eax 0162EF23 e8b80afaff call 0x15cf9e0 <purple_prpl_got_user_status@plt> so that it will push exactly one zero onto the stack, so it gets what it wants (an empty null-terminated list)? Then my only mistake was to assume that [] would automatically generate a null terminated list (for automagic[TM] C-friendlyness) just like strings do? _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
