String(unsigned long) constructor reverses digits, e.g. 10 becomes "01" #5585
Description
Arduino 1.8.15
ESP32 v2.0.0-rc-1
ESP32-S2-WROVER (Saola 1)
String() constructor from unsigned long reverses digits.
Code:
void setup() {
Serial.begin(115200);
delay(100);
for(unsigned long ul = 0; ul < 25; ul++) {
Serial.println(String(ul));
}
}
void loop() {
}
Output:
0
1
2
3
4
5
6
7
8
9
01
11
21
31
41
51
61
71
81
91
02
12
22
32
42
After some more testing I found that the problem is actually with ultoa(), and also ltoa(). The String(unsigned long) constructor uses ultoa() for the conversion, while String(long) uses sprintf("%ld") when base is 10 (which works as expected), and ltoa() for other cases, which fail.
So, both ltoa() and ultoa() reverse digits.
unsigned long value = 123456789;
char buf[10];
ultoa(value, buf, 10);
Serial.print(buf);
produces "987654321"