Max int is returned as 0 when compiled to js

[a-h-mzd]

This code actually returns the maximum int value when run on other platforms like mac but returns 0 when compiled to js

void main() {
  print('max: ${1 << 32}');
}

Dart SDK version: 3.5.4 (stable)

[eernstg]

Check out this page: https://dart.dev/guides/language/numbers, and perhaps this appendix.

When Dart is compiled to JavaScript, numbers are JavaScript numbers (because anything else would be much more expensive in terms of time and space). This has many implications. One of them is that bit operations are based on the web semantics (but the semantics isn't identical to the semantics of JavaScript numbers doing bit operations, because that turned out to be less breaking than just using the JavaScript semantics directly).

In particular, the bitwise operation semantics for Dart-compiled-to-JavaScript is to truncate the operands to 32 bit two'- complement values, perform the bit operation, and interpret the result as an unsigned 32 bit value.

So when you shift 1 to the left by 32 steps then you get 32 zeros (and the single digit which is 1 is the one that just got pushed out of the bit array of length 32, that is, it was lost due to an overflow). Consequently, the result is 0.

By the way, 2^32 is not the maximal value of any binary integer representation (except if you invent a new, surprising one ;-), but 2^32 - 1 could be it (e.g., unsigned 32 bit values, two's complement).

[dart-github-bot]

Summary: The code snippet, intended to print the maximum integer value, returns 0 when compiled to JavaScript, but correctly returns the maximum value on other platforms like macOS. This discrepancy suggests a potential issue with the JavaScript compilation process.