If you manage to get yourself a system where we don't define USE_EVP_AES_CTR (eg, ARM + Sid), and we have a very recent (1.1?) OpenSSL, you get these errors: ``` src/common/aes.c:147:20: error: field ‘evp’ has incomplete type EVP_CIPHER_CTX evp; ^~~ src/common/aes.c: In function ‘evaluate_ctr_for_aes’: src/common/aes.c:243:5: error: implicit declaration of function ‘AES_ctr128_encrypt’ [-Werror=implicit-function-declaration] AES_ctr128_encrypt(&zero[i], &output[i], 1, &key, ivec, ivec_tmp, &pos); ^~~~~~~~~~~~~~~~~~ src/common/aes.c:243:5: error: nested extern declaration of ‘AES_ctr128_encrypt’ [-Werror=nested-externs] CC src/common/crypto_s2k.o cc1: all warnings being treated as errors ```