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https://github.com/arendst/Tasmota.git
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ad671a557c
* wrap printf with stubs * Remove flash savings message from wrap_printf Removed print statement indicating flash savings for ESP8266. * safe more by using rom function
77 lines
2.5 KiB
C++
77 lines
2.5 KiB
C++
/*
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* Linker wrap stubs for FILE*-based printf functions.
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*
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* The ESP8266 Arduino framework and libraries may reference printf(),
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* vprintf(), and fprintf() which pull in newlib's _vfprintf_r (~900 bytes).
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* Tasmota never uses these for logging - log output is written directly to
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* the UART via Arduino's Serial - so the libc FILE*-based printf path is
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* effectively dead code.
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*
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* These stubs redirect through vsnprintf() (already in the binary for
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* Tasmota's logging) and fwrite(), allowing the linker to dead-code
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* eliminate _vfprintf_r.
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*
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* Saves ~1.6 KB of flash.
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*
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* Activated via -Wl,--wrap=vprintf -Wl,--wrap=printf -Wl,--wrap=fprintf
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* (added by pio-tools/wrap_printf.py for ESP8266 builds).
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*
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* Define USE_FULL_PRINTF to disable these stubs and keep the full newlib
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* printf path.
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*/
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#if defined(ESP8266) && !defined(USE_FULL_PRINTF)
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#include <cstdarg>
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#include <cstdio>
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#include <cstdlib>
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#include <ets_sys.h> // declares ets_vprintf and ets_putc
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static constexpr size_t PRINTF_BUFFER_SIZE = 128;
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// These stubs are essentially dead code at runtime - Tasmota writes directly
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// to the UART via Arduino's Serial, and Serial.printf() has its own
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// implementation. The buffer overflow check is purely defensive and should
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// never trigger.
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static int write_printf_buffer(FILE *stream, const char *buf, int len) {
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if (len < 0) return len;
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size_t write_len = (len < (int)PRINTF_BUFFER_SIZE) ? (size_t)len : PRINTF_BUFFER_SIZE - 1;
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fwrite(buf, 1, write_len, stream);
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return len; // return original vsnprintf result (POSIX-compatible)
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}
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// NOLINTBEGIN(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp,readability-identifier-naming)
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extern "C" {
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int __wrap_vprintf(const char *fmt, va_list ap) {
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// ets_putc is a ROM function — zero flash cost
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return ets_vprintf(ets_putc, fmt, ap);
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}
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int __wrap_printf(const char *fmt, ...) {
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va_list ap;
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va_start(ap, fmt);
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int len = __wrap_vprintf(fmt, ap);
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va_end(ap);
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return len;
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}
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int __wrap_fprintf(FILE *stream, const char *fmt, ...) {
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va_list ap;
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va_start(ap, fmt);
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int len;
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if (stream == stdout || stream == stderr || stream == NULL) {
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len = __wrap_vprintf(fmt, ap);
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} else {
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char buf[PRINTF_BUFFER_SIZE];
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len = write_printf_buffer(stream, buf, vsnprintf(buf, sizeof(buf), fmt, ap));
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}
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va_end(ap);
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return len;
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}
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} // extern "C"
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// NOLINTEND(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp,readability-identifier-naming)
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#endif // ESP8266 && !USE_FULL_PRINTF
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