A path from WiFiAP.cpp is automatically appended to my C array

I have a C array like this. (Image 1)

But after I compiled, why is this string automatically appended to my string? (Image 2)


It has broken my HTML content (Image 3)


platform = espressif32
board = esp32dev
framework = arduino
lib_ldf_mode = deep
lib_deps = 
	adafruit/Adafruit GFX Library@^1.11.9
	adafruit/Adafruit SSD1306@^2.5.7

How do I fix it? Thanks!

Sorry because the uploader doesn’t allow me to upload multiple images.

Can you uplaod the project files verbatim?



const char indexHtml[] PROGMEM = {
6d, 0x6c, 0x3e};

array is declared to be of const char [], aka a C-string, but it fails to have a zero-terminator at the end of the array. This is not automatically added in the array.

So, the Serial.println(const char*) function just prints data starting at the pointer you give it until it encounters a null-byte (the zero terminator). Since you have none in your array, it goes beyond its bounds and prints whatever happens to be after the array until it does hit a zero byte.

Simply add a 0x00 as the last element of the array to make it valid C-string.

Otherewise, you could have also called the Serial.println() overload that takes a pointer and length, that is

// does not print beyond bounds
Serial.println((const uint8_t*) indexHtml, sizeof(indexHtml));
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Ah, I just printed it to only for testing.
Btw, I fixed it. Thanks so much!

Also, instead of storing HTML as a hex char array, you should either look into

  • using C++ raw strings (R"()") to place the readable HTML in it direclty (Multiline String in C and C++)
  • save the verbatim HTML file in data/ and use the file system capabilities like LittleFS / SPIFFS to serve it. (docs, tutorial))
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