How to use <iostream> of C++, time() rand() srand() of C, at Enclave.cpp

[MoonHasSevenColor]

Hello Intel Community,

  May I ask how can I use std::cout at Enclave.cpp? And time(), rand() and srand() of C standard libraries?

  I have tried above functions, but it reports undefined reference error for time(), rand() and srand(). And error: cout is not a member of std, when I has written #include <iostream> reference. Thank you!

 I attach the code for your review:) if needed. You can make at the root, and then ./app 

 Have a nice day! 

Best Regards,

Jin Xin

[Wan_Intel]

Hello MoonHasSevenColor,

Thanks for reaching out to us.

Let me check with relevant team and I'll update you as soon as possible.

Regards,

Wan

[Wan_Intel · Accepted solution]

Hello MoonHasSevenColor,

Thanks for your patience.

Referring to Page 472 in Intel® SGX Developer Reference Linux 2.20 Open Source document, std::cout from class <iostream> is not supported by Intel® SGX. As a workaround to accessing <iostream> functions within an Enclave, create an Ocall that calls the <iostream> functions in the untrusted app on behalf of the enclave.

The following example in the Intel® SGX Software Development Kit (Intel® SGX) demonstrates how to implement an Ocall for using printf within an enclave:

https://github.com/intel/linux-sgx/tree/master/SampleCode/SampleEnclave

On another note, referring to pages 468 and 469 in Intel® SGX Developer Reference Linux 2.20 Open Source document, time(), rand(), and srand() are not supported by Intel® SGX. As a workaround for rand() and srand(), enclave developers should use the sgx_read_rand function to get true random numbers.

For more information, please refer to the following page in Intel® SGX Developer Reference Linux 2.20 Open Source document and links:

• Page 466 - Unsupported C Standard Functions
• Page 469 - Unsupported C++ Standard Classes and Functions
• https://www.intel.com/content/www/us/en/support/articles/000058765/software/intel-security-products.html
• https://github.com/intel/linux-sgx/tree/master/SampleCode

Regards,

Wan

[MoonHasSevenColor]

Dear Wan,

  Sorry for the late reply! Thank you for your patient and nice answer, it helps a lot. Thank you!

Best Regards,

Jin Xin

[Wan_Intel]

Hello MoonHasSevenColor,

Thanks for your question.

If you need additional information from Intel, please submit a new question as this thread will no longer be monitored.

Regards,

Wan