digitalmars.D.learn - My is the order of parameters reversed for functions that are
- David Nies (55/55) Nov 15 2015 Apparantly, the order in which parameters are passed to a
- David Nadlinger (6/7) Nov 15 2015 Whenever you use a C function, it must be marked as, even if it's
- David Nies (4/11) Nov 15 2015 How do I mark it as such? Can you please give an example?
- Andrea Fontana (2/15) Nov 15 2015 I think he refers to this: http://dlang.org/interfaceToC.html
- David Nadlinger (3/5) Nov 15 2015 Just add extern(C) to the beginning of the "alias" line.
- David Nies (3/9) Nov 15 2015 Great! Thanks to all of you! That was really quick and helpful!
Apparantly, the order in which parameters are passed to a dynamically loaded C function is reversed. See the following minimal example: ---------------- %> cat dll.c #include "stdio.h" int dll2(const char* first, const char* second) { printf("dll2() - first: '%s', second: '%s'\n", first, second); return 0; } int dll3(const char* first, const char* second, const char* third) { printf("dll3() - first: '%s', second: '%s', third: '%s'\n", first, second, third); return 0; } ---------------- I compiled it with the following commands: %> gcc -c dll.c -fpic %> gcc -shared -o libdll.dyld dll.o %> file libdll.dyld libdll.dyld: Mach-O 64-bit dynamically linked shared library x86_64 Now, I'm using it with a very simple D program and see very unexpected results: ---------------- %> cat main.d import std.stdio, std.string, core.sys.posix.dlfcn; // extern functions alias nothrow int function(const char*, const char*) dll2_fn; alias nothrow int function(const char*, const char*, const char*) dll3_fn; void main() { string sdlLibPath = "libdll.dyld"; auto libraryHandle = dlopen(sdlLibPath.toStringz(), RTLD_LAZY); scope(exit) dlclose(libraryHandle); dll2_fn dll2 = cast(dll2_fn)dlsym(libraryHandle, "dll2"); dll2("one", "two"); dll3_fn dll3 = cast(dll3_fn)dlsym(libraryHandle, "dll3"); dll3("one", "two", "three"); } %> rdmd main.d dll2() - first: 'two', second: 'one' dll3() - first: 'three', second: 'two', third: 'one' ---------------- The order in which the C functions get the parameters is exactly the reverse order in which I supply them in D. What is happening there? I also tried to export a function that has two different types from the C library. Calling it the same way from the client D program causes a segfault - which I'd expect when the parameters are really reversed. How can I make sure the order is correct?
Nov 15 2015
On Sunday, 15 November 2015 at 17:54:27 UTC, David Nies wrote:How can I make sure the order is correct?Whenever you use a C function, it must be marked as, even if it's through a function pointer as in this case. Just apply the attribute to the dll2_fn and dll3_fn declarations. Hope this helps, David
Nov 15 2015
On Sunday, 15 November 2015 at 18:00:09 UTC, David Nadlinger wrote:On Sunday, 15 November 2015 at 17:54:27 UTC, David Nies wrote:How do I mark it as such? Can you please give an example? Thanks for the quick reply! :)How can I make sure the order is correct?Whenever you use a C function, it must be marked as, even if it's through a function pointer as in this case. Just apply the attribute to the dll2_fn and dll3_fn declarations. Hope this helps, David
Nov 15 2015
On Sunday, 15 November 2015 at 18:02:01 UTC, David Nies wrote:On Sunday, 15 November 2015 at 18:00:09 UTC, David Nadlinger wrote:I think he refers to this: http://dlang.org/interfaceToC.htmlOn Sunday, 15 November 2015 at 17:54:27 UTC, David Nies wrote:How do I mark it as such? Can you please give an example? Thanks for the quick reply! :)How can I make sure the order is correct?Whenever you use a C function, it must be marked as, even if it's through a function pointer as in this case. Just apply the attribute to the dll2_fn and dll3_fn declarations. Hope this helps, David
Nov 15 2015
On Sunday, 15 November 2015 at 18:02:01 UTC, David Nies wrote:How do I mark it as such? Can you please give an example? Thanks for the quick reply! :)Just add extern(C) to the beginning of the "alias" line. — David
Nov 15 2015
On Sunday, 15 November 2015 at 18:12:52 UTC, David Nadlinger wrote:On Sunday, 15 November 2015 at 18:02:01 UTC, David Nies wrote:Great! Thanks to all of you! That was really quick and helpful!How do I mark it as such? Can you please give an example? Thanks for the quick reply! :)Just add extern(C) to the beginning of the "alias" line. — David
Nov 15 2015