diff --git a/esphome/components/esp32/printf_stubs.cpp b/esphome/components/esp32/printf_stubs.cpp index 386fbbd79d1..908b4023ead 100644 --- a/esphome/components/esp32/printf_stubs.cpp +++ b/esphome/components/esp32/printf_stubs.cpp @@ -13,14 +13,21 @@ * 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 + * 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. + * On picolibc (default for IDF >= 5 on RISC-V, IDF >= 6 everywhere) we + * route output through a stack-allocated cookie FILE that forwards each + * byte to the real target stream via fputc(). Picolibc's tinystdio + * vfprintf walks the FILE::put callback one character at a time, so this + * costs ~32 bytes of stack for the cookie struct vs. a 512-byte format + * buffer. The buffered path overflows the loopTask stack on IDF 6. * - * Saves ~11 KB of flash. + * On newlib (IDF <= 5 on Xtensa) we keep the original snprintf-then-fwrite + * path because that loopTask stack budget has plenty of headroom for the + * 512-byte buffer; the picolibc-only crash above does not affect it. + * + * Saves ~11 KB of flash on newlib, ~2.8 KB on picolibc. * * To disable these wraps, set enable_full_printf: true in the esp32 * advanced config section. @@ -30,10 +37,55 @@ #include #include +#ifndef __PICOLIBC__ #include "esp_system.h" +#endif namespace esphome::esp32 {} +// NOLINTBEGIN(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp,readability-identifier-naming) +extern "C" { + +#ifdef __PICOLIBC__ + +#include +#include + +extern int __real_vfprintf(FILE *stream, const char *fmt, va_list ap); + +namespace { + +struct CookieFile { + FILE base; + FILE *target; +}; + +// cookie_put() recovers CookieFile* from FILE* via reinterpret_cast, which is +// only well-defined when FILE is the first member at offset 0 and CookieFile +// is standard-layout. +static_assert(offsetof(CookieFile, base) == 0, "FILE must be the first member of CookieFile"); +static_assert(std::is_standard_layout::value, "CookieFile must be standard-layout"); + +int cookie_put(char c, FILE *stream) { + auto *cookie = reinterpret_cast(stream); + return fputc(static_cast(c), cookie->target); +} + +const FILE COOKIE_FILE_TEMPLATE = FDEV_SETUP_STREAM(cookie_put, nullptr, nullptr, _FDEV_SETUP_WRITE); + +} // namespace + +int __wrap_vfprintf(FILE *stream, const char *fmt, va_list ap) { + CookieFile cookie; + cookie.base = COOKIE_FILE_TEMPLATE; + cookie.target = stream; + return __real_vfprintf(&cookie.base, fmt, ap); +} + +int __wrap_vprintf(const char *fmt, va_list ap) { return __wrap_vfprintf(stdout, fmt, ap); } + +#else // !__PICOLIBC__ + static constexpr size_t PRINTF_BUFFER_SIZE = 512; // These stubs are essentially dead code at runtime — ESPHome replaces the @@ -55,14 +107,18 @@ static int write_printf_buffer(FILE *stream, char *buf, int len) { 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_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)); +} + +#endif // __PICOLIBC__ + int __wrap_printf(const char *fmt, ...) { va_list ap; va_start(ap, fmt); @@ -71,11 +127,6 @@ int __wrap_printf(const char *fmt, ...) { 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);