Bug #22087: Octal format specifier in alternatve form ignores zero precision if value is zero

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 4.1.0dev (2026-05-29T14:34:40Z master 7a07a54298) +PRISM [x86_64-linux]
• Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN

[Earlopain (Earlopain _)]

For integer types, it is documented that zero as a value results in empty output:
https://docs.ruby-lang.org/en/4.0/language/format_specifications_rdoc.html#:~:text=If%20the%20precision%20is%200%20and%20the%20value%20is%200%2C%20nothing%20is%20written

This applies when # is not given. But with #, the octal format violates that statement:

pp sprintf("%#.0b", 0) # => ""
pp sprintf("%#.0B", 0) # => ""
pp sprintf("%#.0x", 0) # => ""
pp sprintf("%#.0X", 0) # => ""
pp sprintf("%#.0o", 0) # => "0"

[nobu (Nobuyoshi Nakada)]

I believe this behavior is designed to conform to the printf in ISO/IEC 9899.

[Earlopain (Earlopain _)]

• Status changed from Open to Rejected

Ah, indeed. It looked it up an you are right. From https://en.cppreference.com/c/io/fprintf

x/X:

In the alternative implementation 0x or 0X is prefixed to results if the converted value is nonzero.

o:

In the alternative implementation precision is increased if necessary, to write one leading zero. In that case if both the converted value and the precision are 0, single 0 is written.