v0.31.0

What's Changed

• Abstract TLS API support (Resolve #2309) by @yhirose in #2342
• Add C++ modules support by @mikomikotaishi in #2291
• Fix #2339 by @yhirose in #2344
• Fix #2116 by @yhirose in #2346
• Fix memory leak by @yhirose in #2348

Breaking Changes

1. Default value change for CPPHTTPLIB_PAYLOAD_MAX_LENGTH

• Old: std::numeric_limits<size_t>::max() (effectively unlimited)
• New: 100 * 1024 * 1024 (100MB)
• Code that receives payloads larger than 100MB will now fail with ExceedMaxPayloadSize error

2. Introduction of the TLS Abstraction Layer (Abstract TLS API)

• Mbed TLS can now be used by defining CPPHTTPLIB_MBEDTLS_SUPPORT
• Request::ssl (SSL* type) has been removed and replaced with Request::ssl (tls::const_session_t type)
• ClientConnection::ssl has similarly been changed to tls::session_t
• Constructors and methods that directly use OpenSSL types (X509*, EVP_PKEY*, etc.) are now deprecated
• SSLServer: X509*/EVP_PKEY* constructors → migrate to SSLServer(PemMemory) or SSLServer(ContextSetupCallback)
• SSLClient: ssl_context() → use tls_context() instead
• Client: set_server_certificate_verifier(std::function<SSLVerifierResponse(SSL*)>) → use set_server_certificate_verifier(tls::VerifyCallback) instead
• Result: ssl_openssl_error() → use ssl_backend_error() instead
• Request: req.ssl (OpenSSL SSL*) → req.ssl (tls::const_session_t) + use req.peer_cert() / req.sni()