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https://github.com/esphome/esphome.git
synced 2026-09-12 15:57:33 +00:00
Jesse Hills
bfb8569636
Linking an HTTPS client (http_request, mqtt) pulls in TLS features no ESPHome client ever negotiates: the server-side handshake, static RSA and static ECDH key exchange, renegotiation, session tickets, AES-CCM suites, the EC private-key parsing extras and deterministic ECDSA. Two new esp32 advanced options, on by default, turn them off and save around 14 KB per build; OpenThread opts back in through require hooks because its DTLS commissioner is a server and it uses CCM and deterministic ECDSA directly. On the ESP32-C6 the ROM exports a full-format vsnprintf but no vasprintf, so esp_http_client's vasprintf call was the only thing dragging newlib's printf engine (~20 KB) into the image. A linker-wrapped vasprintf built on the ROM vsnprintf keeps it out.
53 lines
1.7 KiB
C++
53 lines
1.7 KiB
C++
/*
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* Linker wrap stub for vasprintf() on variants whose ROM exports a
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* full-format vsnprintf() but no vasprintf() (ESP32-C6, newlib only).
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*
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* On those chips every snprintf/vsnprintf call in the image resolves to
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* the ROM, so the newlib printf engine (_svfprintf_r, _dtoa_r and their
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* helpers, ~20 KB) is not linked at all until something references a
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* printf-family function the ROM lacks. esp_http_client does exactly that
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* through vasprintf() in its header and auth helpers, so adding
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* http_request to a build costs the whole engine on top of the HTTP and
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* TLS code itself.
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*
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* This stub reimplements vasprintf() on top of the ROM vsnprintf(), which
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* keeps the engine out of the image. It is only compiled in when codegen
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* defines USE_ESP32_VASPRINTF_STUB, which is gated on the variant's ROM
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* linker script and on the same newlib condition as printf_stubs.cpp.
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*/
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#include "esphome/core/defines.h"
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#if defined(USE_ESP_IDF) && defined(USE_ESP32_VASPRINTF_STUB)
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#include <cstdarg>
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#include <cstdio>
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#include <cstdlib>
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namespace esphome::esp32 {}
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// NOLINTBEGIN(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp,readability-identifier-naming)
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extern "C" {
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int __wrap_vasprintf(char **strp, const char *fmt, va_list ap) {
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va_list ap_copy;
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va_copy(ap_copy, ap);
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int len = vsnprintf(nullptr, 0, fmt, ap_copy);
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va_end(ap_copy);
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if (len < 0) {
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return len;
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}
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char *buf = static_cast<char *>(malloc(static_cast<size_t>(len) + 1));
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if (buf == nullptr) {
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return -1;
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}
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vsnprintf(buf, static_cast<size_t>(len) + 1, fmt, ap);
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*strp = buf;
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return len;
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}
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} // extern "C"
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// NOLINTEND(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp,readability-identifier-naming)
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#endif // USE_ESP_IDF && USE_ESP32_VASPRINTF_STUB
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