[esp32] Wrap vfprintf to fix printf stub on picolibc (IDF 6) (#15172)

esphome/components/esp32/__init__.py

@@ -1587,7 +1587,7 @@ async def to_code(config):
         if conf[CONF_ADVANCED][CONF_ENABLE_FULL_PRINTF]:
             cg.add_define("USE_FULL_PRINTF")
         else:
-            for symbol in ("vprintf", "printf", "fprintf"):
+            for symbol in ("vprintf", "printf", "fprintf", "vfprintf"):
                 cg.add_build_flag(f"-Wl,--wrap={symbol}")
     else:
         cg.add_build_flag("-DUSE_ARDUINO")

esphome/components/esp32/printf_stubs.cpp

@@ -2,10 +2,11 @@
  * Linker wrap stubs for FILE*-based printf functions.
  *
  * ESP-IDF SDK components (gpio driver, ringbuf, log_write) reference
- * fprintf(), printf(), and vprintf() which pull in newlib's _vfprintf_r
- * (~11 KB). This is a separate implementation from _svfprintf_r (used by
- * snprintf/vsnprintf) that handles FILE* stream I/O with buffering and
- * locking.
+ * 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()
@@ -70,11 +71,15 @@ 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);
-  char buf[PRINTF_BUFFER_SIZE];
-  int len = write_printf_buffer(stream, buf, vsnprintf(buf, sizeof(buf), fmt, ap));
+  int len = __wrap_vfprintf(stream, fmt, ap);
   va_end(ap);
   return len;
 }