I found it: I had a typo writing "C.nil" instead of "nil". thanks for your help!
On Sun, Jun 11, 2017 at 9:31 PM, Ian Lance Taylor <i...@golang.org> wrote: > On Sun, Jun 11, 2017 at 7:56 PM, andrey mirtchovski > <mirtchov...@gmail.com> wrote: >> >> I have a piece of cgo code which doesn't do much, but links a lot of >> libraries in. As far as I can tell all my includes are there and they >> shouldn't stomp on each other (they don't when compiled in C), however >> with cgo I get the following weirdness: >> >> $ go build >> # mypkg >> Undefined symbols for architecture x86_64: >> "___DARWIN_NULL", referenced from: >> __cgohack___DARWIN_NULL in _cgo_main.o >> (maybe you meant: __cgohack___DARWIN_NULL) >> ld: symbol(s) not found for architecture x86_64 >> clang: error: linker command failed with exit code 1 (use -v to see >> invocation) >> >> If I decide to be bold and #define __DARWIN_NULL in my Cgo preamble >> (before "import C"), I get the following: >> >> $ go build >> # mypkg >> ./main.go:53:9: warning: '__DARWIN_NULL' macro redefined [-Wmacro-redefined] >> /usr/include/sys/_types.h:52:9: note: previous definition is here >> >> I'm a little bit stumped. How to debug the chain on #includes to get >> to the bottom of this? Why is this not a problem elsewhere? > > Presumably your Go code is referring to C.__DARWIN_NULL. In some > cases that will cause cgo to generate C code that looks like > extern char __DARWIN_NULL[]; > void *_cgohack___DARWIN_NULL = __DARWIN_NULL; > This kind of thing works for a variable or function, but not for a > macro. This may be a version of https://golang.org/issue/18720. The > simplest fix is to write, in your C preamble, > void *my_DARWIN_NULL = __DARWIN_NULL; // use the appropriate type here > and then refer to C.my_DARWIN_NULL in your Go code. > > Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
