Re: [fpc-pascal] callback from c with varargs
El 20/12/20 a les 14:00, Jonas Maebe via fpc-pascal ha escrit: On 20/12/2020 13:01, Luca Olivetti via fpc-pascal wrote: El 19/12/20 a les 23:15, Jonas Maebe via fpc-pascal ha escrit: It is indeed not possible to implement a function with C varargs in FPC. I was afraid that's the answer :-( as an ugly workaround, I wrote a c library that vsnprintf msg and args to a buffer and then calls a pascal function with no varargs. It works but, as I said, it's ugly and I'd need to provide a .a for every platform I plan to use. Is there a better/simpler way (apart from asking the library developers to use a callback with no varargs)? No. :-( Oh, well, that's life. Now I'm struggling to integrate my stub function under win32 (no problem with linux/64). The linker complains about Error: Undefined symbol: _vsnprintf Error: Undefined symbol: _ua_pascallog the first it's probably because it's missing some library (which?) but the second is defined in my program (and, as I said, it builds and works fine under linux/64) as: procedure ua_pascallog(logContext: Pointer; level: UA_LogLevel; category: UA_LogCategory; msg: PAnsiChar);cdecl;export; Any hint? Bye -- Luca ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] callback from c with varargs
On 20/12/2020 14:43, Tomas Hajny via fpc-pascal wrote: > On 2020-12-20 14:00, Jonas Maebe via fpc-pascal wrote: >> On 20/12/2020 13:01, Luca Olivetti via fpc-pascal wrote: >>> El 19/12/20 a les 23:15, Jonas Maebe via fpc-pascal ha escrit: It is indeed not possible to implement a function with C varargs in FPC. >>> >>> I was afraid that's the answer :-( >>> >>> as an ugly workaround, I wrote a c library that vsnprintf msg and args >>> to a buffer and then calls a pascal function with no varargs. >>> >>> It works but, as I said, it's ugly and I'd need to provide a .a for >>> every platform I plan to use. >>> >>> Is there a better/simpler way (apart from asking the library developers >>> to use a callback with no varargs)? >> >> No. > > Not necessarily better than platform specific .a files mentioned by > Luca, but the required playing with stack and registers should be still > doable with a function written in assembler (inside the Pascal sources), > shouldn't it? Yes, but you'd have to write it separately for each ABI. Jonas ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] callback from c with varargs
On 2020-12-20 14:00, Jonas Maebe via fpc-pascal wrote: On 20/12/2020 13:01, Luca Olivetti via fpc-pascal wrote: El 19/12/20 a les 23:15, Jonas Maebe via fpc-pascal ha escrit: It is indeed not possible to implement a function with C varargs in FPC. I was afraid that's the answer :-( as an ugly workaround, I wrote a c library that vsnprintf msg and args to a buffer and then calls a pascal function with no varargs. It works but, as I said, it's ugly and I'd need to provide a .a for every platform I plan to use. Is there a better/simpler way (apart from asking the library developers to use a callback with no varargs)? No. Not necessarily better than platform specific .a files mentioned by Luca, but the required playing with stack and registers should be still doable with a function written in assembler (inside the Pascal sources), shouldn't it? Tomas ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] callback from c with varargs
On 20/12/2020 13:01, Luca Olivetti via fpc-pascal wrote: > El 19/12/20 a les 23:15, Jonas Maebe via fpc-pascal ha escrit: >> It is indeed not possible to implement a function with C varargs in FPC. > > I was afraid that's the answer :-( > > as an ugly workaround, I wrote a c library that vsnprintf msg and args > to a buffer and then calls a pascal function with no varargs. > > It works but, as I said, it's ugly and I'd need to provide a .a for > every platform I plan to use. > > Is there a better/simpler way (apart from asking the library developers > to use a callback with no varargs)? No. Jonas ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] callback from c with varargs
El 19/12/20 a les 23:15, Jonas Maebe via fpc-pascal ha escrit: On 19/12/2020 22:35, Luca Olivetti via fpc-pascal wrote: I'm trying to use a c library where I can define a logging plugin. The c prototype for the callback is void (*log)(void *logContext, UA_LogLevel level, UA_LogCategory category, const char *msg, va_list args); however I couldn't find a way to define a suitable callback in fpc since the "array of const" construct is not allowed with cdecl without external, i.e. It is indeed not possible to implement a function with C varargs in FPC. I was afraid that's the answer :-( as an ugly workaround, I wrote a c library that vsnprintf msg and args to a buffer and then calls a pascal function with no varargs. It works but, as I said, it's ugly and I'd need to provide a .a for every platform I plan to use. Is there a better/simpler way (apart from asking the library developers to use a callback with no varargs)? Bye -- Luca ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] callback from c with varargs
On 19/12/2020 22:35, Luca Olivetti via fpc-pascal wrote: > I'm trying to use a c library where I can define a logging plugin. > > The c prototype for the callback is > > void (*log)(void *logContext, UA_LogLevel level, UA_LogCategory > category, const char *msg, va_list args); > > > however I couldn't find a way to define a suitable callback in fpc since > the "array of const" construct is not allowed with cdecl without > external, i.e. It is indeed not possible to implement a function with C varargs in FPC. Jonas ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] callback from c with varargs
Hello, I'm trying to use a c library where I can define a logging plugin. The c prototype for the callback is void (*log)(void *logContext, UA_LogLevel level, UA_LogCategory category, const char *msg, va_list args); however I couldn't find a way to define a suitable callback in fpc since the "array of const" construct is not allowed with cdecl without external, i.e. procedure LogLog(logContext: Pointer; level: UA_LogLevel; category: UA_LogCategory; msg: PAnsiChar; const args:array of const);cdecl; gives an error "Error: VarArgs directive (or '...' in MacPas) without CDecl/CPPDecl/MWPascal/StdCall and External". I cannot add "external" (I don't want to call an external function, it's the library calling my function) or remove the cdecl (parameter passing wouldn't work then). Is there some trick to define a function with varargs callable from the c library? Bye -- Luca ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
