Eos: how do deal with assertion failure with message: read

[breadbread1984]

My contract action causes error message

assertion failure with message: read

My action code is here

void GeneMelee::buy(account_name buyer,uint64_t sale_key,asset price)
{
    //check existence
    saletable sales(_self,_self);
    auto which = sales.find(sale_key);
    eosio_assert(sales.end() != which,"no such item on sale");
    //check whether the transferred quantity is over the price
    eosio_assert(price.symbol == which->price.symbol,"the payment is not the seller's required currency!");
    eosio_assert(price.amount >= which->price.amount,"the payment is not enough to buy the item!");
    action(
        permission_level{_self,N(active)},
        N(eosio.token),N(transfer),
        std::make_tuple(_self,which->player,price,"payment from buyer")
    ).send();
    //hand over item
    switch(which->type) {
        case static_cast<int>(ForSale::ELF):
            {
                elftable seller_elfs(_self,which->player);
                auto which_elf = seller_elfs.find(which->item_key);
                eosio_assert(seller_elfs.end() != which_elf,"seller don't have the elf for sale");
                elftable buyer_elfs(_self,buyer);
                buyer_elfs.emplace(_self,[&](auto & elf){
                    elf.elf_key = buyer_elfs.available_primary_key();
                    elf.genre = which_elf->genre;
                    elf.level = which_elf->level;
                    elf.appearance = which_elf->appearance;
                    elf.dna = which_elf->dna;
                    elf.capabilities = which_elf->capabilities;
                    elf.last_feed_datetime = which_elf->last_feed_datetime;
                    elf.feed_interval = which_elf->feed_interval;
                    elf.bgr = which_elf->bgr;
                });
                seller_elfs.erase(which_elf);
            }
            break;
        case static_cast<int>(ForSale::GENE):
            {
                genetable seller_genes(_self,which->player);
                auto which_gene = seller_genes.find(which->item_key);
                eosio_assert(seller_genes.end() != which_gene,"seller don't have the gene for sale");
                genetable buyer_genes(_self,buyer);
                buyer_genes.emplace(_self,[&](auto & gene) {
                    gene.gene_key = buyer_genes.available_primary_key();
                    gene.segment_id = which_gene->segment_id;
                    gene.delta_appearance = which_gene->delta_appearance;
                    gene.delta_capabilities = which_gene->delta_capabilities;
                    gene.delta_bgr = which_gene->delta_bgr;
                });
                seller_genes.erase(which_gene);
            }
            break;
        default:
            eosio_assert(0,"unknown type of item!");
    }
    //remove from saling table
    sales.erase(which);
}

which part of the code could cause the error message? One thing I can't understand is that I added eosio_assert(0,"here"); to the last line of the action. when I call the action, my assertion can always be triggered. it seems the error occurs after the action is called.

[taokayan]

Inline actions are always called after the main action no matter where you put it in your source code.

[breadbread1984]

the problem is caused by not giving memo in string object.

[spartucus]

So

action(
        permission_level{_self,N(active)},
        N(eosio.token),N(transfer),
        std::make_tuple(_self,which->player,price,"payment from buyer")
    ).send();

failed and

action(
        permission_level{_self,N(active)},
        N(eosio.token),N(transfer),
        std::make_tuple(_self,which->player,price,std::string("payment from buyer"))
    ).send();

succeed?
I think it's a bug. And there's someone else met the same issue. see here

[breadbread1984]

@heifner

[tbfleming]

@spartucus that looks like a bug to me too. Please create an issue with your example in the wasmsdk repo; that’s where it needs to be fixed.

[larryk85]

@spartucus This is not a bug per se, it is a limitation of make_tuple. The types const char* and std::string are not the same, so make_tuple will treat the const char* as a pointer and will send over that (which is garbage), and the type of the memo field is expecting an std::string, so explicit construction of std::string is needed to make std::make_tuple do the right thing.