diff --git a/esphome/components/rp2040/__init__.py b/esphome/components/rp2040/__init__.py index 1442a0a7f7..7ee8381ca5 100644 --- a/esphome/components/rp2040/__init__.py +++ b/esphome/components/rp2040/__init__.py @@ -190,6 +190,11 @@ async def to_code(config): ], ) + # Wrap FILE*-based printf functions to eliminate newlib's _vfprintf_r + # (~8.9 KB). See printf_stubs.cpp for implementation. + for symbol in ("vprintf", "printf", "fprintf"): + cg.add_build_flag(f"-Wl,--wrap={symbol}") + cg.add_platformio_option("board_build.core", "earlephilhower") cg.add_platformio_option("board_build.filesystem_size", "1m") diff --git a/esphome/components/rp2040/printf_stubs.cpp b/esphome/components/rp2040/printf_stubs.cpp new file mode 100644 index 0000000000..83d916cd2c --- /dev/null +++ b/esphome/components/rp2040/printf_stubs.cpp @@ -0,0 +1,71 @@ +/* + * Linker wrap stubs for FILE*-based printf functions. + * + * The RP2040 Arduino framework and libraries may reference printf(), + * vprintf(), and fprintf() which pull in newlib's _vfprintf_r (~8.9 KB). + * ESPHome never uses these — all logging goes through the logger component + * which uses snprintf/vsnprintf, so the libc FILE*-based printf path is + * dead code. + * + * These stubs redirect through vsnprintf() (which is already in the binary) + * and fwrite(), allowing the linker to dead-code eliminate _vfprintf_r. + * + * Saves ~8.9 KB of flash. + */ + +#if defined(USE_RP2040) && !defined(USE_FULL_PRINTF) +#include +#include +#include + +namespace esphome::rp2040 {} + +static constexpr size_t PRINTF_BUFFER_SIZE = 512; + +// These stubs are essentially dead code at runtime — ESPHome uses its own +// logging through snprintf/vsnprintf, not libc printf. +// 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); + abort(); + } + 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_fprintf(FILE *stream, const char *fmt, ...) { + va_list ap; + va_start(ap, fmt); + char buf[PRINTF_BUFFER_SIZE]; + int len = write_printf_buffer(stream, buf, vsnprintf(buf, sizeof(buf), fmt, ap)); + va_end(ap); + return len; +} + +} // extern "C" +// NOLINTEND(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp,readability-identifier-naming) + +#endif // USE_RP2040 && !USE_FULL_PRINTF