/* * Linker wrap stubs for FILE*-based printf functions. * * ESP-IDF SDK components (gpio driver, ringbuf, log_write) reference * fprintf(), printf(), vprintf(), and vfprintf() which pull in the full * printf implementation (~11 KB on newlib's _vfprintf_r, ~2.8 KB on * picolibc's vfprintf). This is a separate implementation from the one * used by snprintf/vsnprintf that handles FILE* stream I/O with buffering * and locking. * * 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. * * These stubs redirect through vsnprintf() (which uses _svfprintf_r * already in the binary) and fwrite(), allowing the linker to * dead-code eliminate _vfprintf_r. * * Saves ~11 KB of flash. * * To disable these wraps, set enable_full_printf: true in the esp32 * advanced config section. */ #if defined(USE_ESP_IDF) && !defined(USE_FULL_PRINTF) #include #include #include "esp_system.h" namespace esphome::esp32 {} 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; } // NOLINTBEGIN(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp,readability-identifier-naming) extern "C" { 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_printf(const char *fmt, ...) { va_list ap; va_start(ap, fmt); int len = __wrap_vprintf(fmt, ap); va_end(ap); return len; } 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_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