I want to write a contract by using CPR library. Unfortunately I have an error:

fatal error: 'future' file not found
#include <future>

I am using EOSIO cdt v1.5.0 on Ubuntu 18.04.

I had the same with v1.4.1. I have build the v1.5.0 from the source hoping it will have needed header because I see a file ./libraries/libc++/libcxx/src/future.cpp in the repo.

Can you please help me?

  • i am facing the same issue while making a smart contract using cpr library,did you get any work around it? or any other library instead of cpr that works with eosio? I am using eosio.cdt 1.6.3 on Ubuntu 18.04 LTS Oct 17, 2019 at 13:38
  • No, I dropped that little project.Now I am focused on other that does not have such need to use future . Oct 17, 2019 at 13:58
  • I see, but is there any way to implement response request of API in smart contract in eosio? and did you find anything? Oct 18, 2019 at 9:53

1 Answer 1


It isn't possible to use future in smart contracts, because the whole thing is single-thread C++. Multithreading isn't supported and wouldn't work within the contract because it would potentially make the results of any code non-deterministic

  • I understand your opinion, but I found a 'thread' header file in eosio.cdt directory. file /usr/local/eosio.cdt/include/libcxx/thread Feb 25, 2019 at 19:15
  • It isn't an opinion. If the smart contract was non-deterministic, then it wouldn't make sense to have it on a blockchain. Sorry but thats kind of in the definition. Perhaps B1 forgot to take it away when they built their libraries? Feb 25, 2019 at 19:17

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