/* * Linker wrap stubs for FILE*-based printf functions (newlib only). * * ESP-IDF SDK components (gpio driver, ringbuf, log_write) reference * fprintf(), printf(), vprintf(), and vfprintf(), which on newlib pull * in _vfprintf_r (~11 KB) — a separate implementation from the one used * by snprintf/vsnprintf that handles FILE* stream I/O with buffering. * * ESPHome replaces the ESP-IDF log handler via esp_log_set_vprintf_(), * so the SDK's vprintf() path is dead code at runtime. The fprintf() * and printf() calls in SDK components are only in debug/assert paths * (gpio_dump_io_configuration, ringbuf diagnostics) that are either * GC'd or never called. Crash backtraces and panic output are * unaffected; they use esp_rom_printf() which is a ROM function and * does not go through libc. * * This wrap is newlib-only. On picolibc, vsnprintf is implemented as * vfprintf into a string-output FILE, so vfprintf is unconditionally * linked in by any caller of snprintf/vsnprintf and the wrap can never * elide it — it just adds shim cost. Codegen forces USE_FULL_PRINTF * on picolibc builds (IDF 6.0+ on all variants) so this file compiles * to nothing there; the #error below catches a desynchronised gate. * * Saves ~11 KB of flash on newlib. * * To disable this wrap on newlib, set enable_full_printf: true in the * esp32 advanced config section. */ #if defined(USE_ESP_IDF) && !defined(USE_FULL_PRINTF) #ifdef __PICOLIBC__ #error "printf wrap is net-negative on picolibc; codegen should set USE_FULL_PRINTF" #endif #include #include #include "esp_system.h" namespace esphome::esp32 {} // NOLINTBEGIN(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp,readability-identifier-naming) extern "C" { static constexpr size_t PRINTF_BUFFER_SIZE = 512; // These stubs are essentially dead code at runtime — ESPHome replaces the // ESP-IDF log handler, and the SDK's printf/fprintf calls only exist in // debug/assert paths that are never reached in normal operation. // The buffer overflow check is purely defensive and should never trigger. static int write_printf_buffer(FILE *stream, char *buf, int len) { if (len < 0) { return len; } size_t write_len = len; if (write_len >= PRINTF_BUFFER_SIZE) { fwrite(buf, 1, PRINTF_BUFFER_SIZE - 1, stream); esp_system_abort("printf buffer overflow; set enable_full_printf: true in esp32 framework advanced config"); } if (fwrite(buf, 1, write_len, stream) < write_len || ferror(stream)) { return -1; } return len; } int __wrap_vprintf(const char *fmt, va_list ap) { char buf[PRINTF_BUFFER_SIZE]; return write_printf_buffer(stdout, buf, vsnprintf(buf, sizeof(buf), fmt, ap)); } int __wrap_vfprintf(FILE *stream, const char *fmt, va_list ap) { char buf[PRINTF_BUFFER_SIZE]; return write_printf_buffer(stream, buf, vsnprintf(buf, sizeof(buf), fmt, ap)); } int __wrap_printf(const char *fmt, ...) { va_list ap; va_start(ap, fmt); int len = __wrap_vprintf(fmt, ap); va_end(ap); return len; } int __wrap_fprintf(FILE *stream, const char *fmt, ...) { va_list ap; va_start(ap, fmt); int len = __wrap_vfprintf(stream, fmt, ap); va_end(ap); return len; } } // extern "C" // NOLINTEND(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp,readability-identifier-naming) #endif // USE_ESP_IDF && !USE_FULL_PRINTF