unique_ptr arguments. error C2664

Question

I recently just heard of the new unique_ptr in C++11 and wanted to try it.

I changed this code :

void CreateDummySpell(uint32 id)
{
    const char * name = "Dummy Trigger";
    SpellEntry * sp = new SpellEntry;
    memset(sp, 0, sizeof(SpellEntry));
    sp->Id = id;
    sp->Attributes = 384;
    sp->AttributesEx = 268435456;
    sp->AttributesExB = 4;
    sp->CastingTimeIndex=1;
    sp->procChance=75;
    sp->rangeIndex=13;
    sp->EquippedItemClass=uint32(-1);
    sp->Effect[0]=3;
    sp->EffectImplicitTargetA[0]=25;
    sp->NameHash=crc32((const unsigned char*)name, (unsigned int)strlen(name));
    sp->dmg_multiplier[0]=1.0f;
    sp->StanceBarOrder=-1;
    dbcSpell.SetRow(id,sp);
    sWorld.dummyspells.push_back(sp);
}

to this

void CreateDummySpell(uint32 id)
{
    const char * name = "Dummy Trigger";
//  SpellEntry * sp = new SpellEntry;
    std::unique_ptr<SpellEntry> sp(new SpellEntry);
    memset(sp, 0, sizeof(SpellEntry));
    sp->Id = id;
    sp->Attributes = 384;
    sp->AttributesEx = 268435456;
    sp->AttributesExB = 4;
    sp->CastingTimeIndex=1;
    sp->procChance=75;
    sp->rangeIndex=13;
    sp->EquippedItemClass=uint32(-1);
    sp->Effect[0]=3;
    sp->EffectImplicitTargetA[0]=25;
    sp->NameHash=crc32((const unsigned char*)name, (unsigned int)strlen(name));
    sp->dmg_multiplier[0]=1.0f;
    sp->StanceBarOrder=-1;
    dbcSpell.SetRow(id,sp);
    sWorld.dummyspells.push_back(sp);
}

Now I'm getting this error :

error C2664: 'void *memset(void *,int,size_t)': cannot convert argument 1 from 'std::unique_ptr<SpellEntry,std::default_delete<_Ty>>' to 'void *'
2>          with
2>          [
2>              _Ty=SpellEntry
2>          ]
2>  ..\..\src\arcemu-world\SpellFixes.cpp(29): note: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
2>..\..\src\arcemu-world\SpellFixes.cpp(43): error C2664: 'void DBCStorage<SpellEntry>::SetRow(uint32,T *)': cannot convert argument 2 from 'std::unique_ptr<SpellEntry,std::default_delete<_Ty>>' to 'SpellEntry *'
2>          with
2>          [
2>              T=SpellEntry
2>          ]
2>          and
2>          [
2>              _Ty=SpellEntry
2>          ]
2>  ..\..\src\arcemu-world\SpellFixes.cpp(43): note: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
2>..\..\src\arcemu-world\SpellFixes.cpp(44): error C2664: 'void std::list<SpellEntry *,std::allocator<_Kty>>::push_back(const _Ty &)': cannot convert argument 1 from 'std::unique_ptr<SpellEntry,std::default_delete<_Ty>>' to 'SpellEntry *&&'
2>          with
2>          [
2>              _Kty=SpellEntry *
2>  ,            _Ty=SpellEntry *
2>          ]
2>          and
2>          [
2>              _Ty=SpellEntry
2>          ]
2>  ..\..\src\arcemu-world\SpellFixes.cpp(44): note: Reason: cannot convert from 'std::unique_ptr<SpellEntry,std::default_delete<_Ty>>' to 'SpellEntry *'
2>          with
2>          [
2>              _Ty=SpellEntry
2>          ]
2>  ..\..\src\arcemu-world\SpellFixes.cpp(44): note: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

It seems like I can pass sp as arguments. How do you pass sp as argument using unique_ptr smart pointers?

Thanks in advance.

---

too short message...

Answer 1

You should probably reconsider using memset (and just value-initialize it e.g new SomeClass() ) but in the general case if you want to pass the internal pointer of a unique_ptr (e.g to a legacy function) use its get function.