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jsonlinker-errorsglibvala

Linker can't find 'get_int_member_with_default' from json-glib

I am currently working on a library that interacts with a REST API. This API responds with a JSON object, which I'm parsing with json-glib-1.0. As some of the members of the object might not exist I wanted to use the get_x_member_with_default function of the Json.Object class. Even though both the Vala and the C compiler see the functions the linker gives me several errors:

Undefined symbols for architecture x86_64:
  "_json_object_get_boolean_member_with_default", referenced from:
      _discord_message_construct in message-f5c60f.o
  "_json_object_get_int_member_with_default", referenced from:
      _discord_message_construct in message-f5c60f.o
  "_json_object_get_string_member_with_default", referenced from:
      _discord_message_construct in message-f5c60f.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

To reproduce this you can try this code:

void main() {
    string json = "{\"one\": 1337}";
    Json.Parser parser = new Json.Parser();
    parser.load_from_data(json, -1);
    int64 val = parser.get_root().get_object().get_int_member_with_default("one", 666);
    stdout.printf(@"$val\n");
}

and compile it with this command: valac --pkg json-glib-1.0 file.vala. This gives me

Undefined symbols for architecture x86_64:
  "_json_object_get_int_member_with_default", referenced from:
      __vala_main in json2-ec99c2.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

This is obviously not a library; when compiling my library I only generate the C code and compile and link everything with the output of pkg-config --cflags --libs json-glib-1.0. Is there anything I have to link additionally?

Solution

  • You need to install a newer version of json-glib, or more likely, not use that symbol. The Vala documentation for the symbol shows this is since version 1.6 of the library. This information is taken from the C source for the library and the symbol was added with this commit. The problem is the latest stable release appears to be 1.4.4 - see the source repository tags. So it looks like you have to build your own development version with the latest symbols or not use get_int_member_with_default ().