Creating array of structs being used in C interface

[Nicholas Wilson via Digitalmars-d-learn]

On Sunday, 27 November 2016 at 12:59:32 UTC, Timoses wrote:
> Hi there,
>
> I've got a problem interfacing to a C library.
> The following structs are used by the library's .d file that 
> I've written.
>
> --------------------
> struct neo4j_map_entry_t
> {
>     neo4j_value_t key;
>     neo4j_value_t value;
> };
>
> struct neo4j_value_t
> {
>     uint8_t _vt_off;
>     uint8_t _type; /*TODO: combine with _vt_off? (both always 
> have same value)*/
>     uint16_t _pad1;
>     uint32_t _pad2;
>     _neo4j_value_data _vdata;
> };
>
> union _neo4j_value_data
> {
>     uint64_t _int;
>     uintptr_t _ptr;
>     double _dbl;
> };
> --------------------
>
> Now I'd also like to use them in my own code. However, I fail 
> at generating an array of map entries:
>
> --------------------
> void test()
> {
>     // These work
>     neo4j_map_entry_t[] mapa2; // yes
>     neo4j_map_entry_t entry1 = { key: neo4j_string("prop1"), 
> value: neo4j_string("testprop1")}; // yes
>     neo4j_map_entry_t entry2 = { key: neo4j_string("prop2"), 
> value: neo4j_string("testprop2")}; // yes
>     neo4j_map_entry_t* mapp; // yes
>
>     // These don't
>     neo4j_map_entry_t[2] mapa1; // no
>     mapa2.length = 2; // no
>     mapa2 ~= entry1; // no
>     neo4j_map_entry_t[] mapa3 = [{ key: neo4j_null, value: 
> neo4j_null}]; // no
> }
> --------------------
>
> The output is:
> ______________________
> myprogram ~master: building configuration "unittest"...
> Linking...
> Undefined symbols for architecture x86_64:
>   "_D10neo4jTypes17neo4j_map_entry_t6__initZ", referenced from:
>       _D6myprogram6myprogram5test2MFZv in myprogram.o
> ld: symbol(s) not found for architecture x86_64
> ______________________
>
> Why is it a linker problem? I'm not linking to the c interface 
> but merely using D structs...

The missing symbol is the struct initialiser for 
neo4j_map_entry_t. Not sure why is not being generated (it 
should), possibly because of the union.

That seems like a bug please report it. http://issues.dlang.org/