From: "mame (Yusuke Endoh) via ruby-core" Date: 2023-01-20T04:37:50+00:00 Subject: [ruby-core:111918] [Ruby master Feature#19245] Strict mode for Array#pack that doesn't silently truncate numbers that are too large for the given directive Issue #19245 has been updated by mame (Yusuke Endoh). Discussed at the dev meeting. We need to determine some detailed behaviors: * Should `[-1].pack("C", strict: true)` raise an exception because 'C' represents unsigned char? If what you want is "wrap around", it should raise an error because `[-1].pack("C").unpack1("C")` returns 255, not -1. * Should `[255].pack("c", strict: true)` raise an exception? * Should `["foo"].pack("a2", strict: true)` raise an exception? * Should `["f"].pack("a2", strict: true)` raise an exception? * Perhaps we need to consider what is out of range for each format. And just for the record: @nobu proposed a new modifier to check out-of-range value, such as `[256].pack("c^") #=> error`. This allows users to determine out-of-range policy per element in one format. However, @matz disliked it. ---------------------------------------- Feature #19245: Strict mode for Array#pack that doesn't silently truncate numbers that are too large for the given directive https://bugs.ruby-lang.org/issues/19245#change-101341 * Author: byroot (Jean Boussier) * Status: Open * Priority: Normal ---------------------------------------- ```ruby >> [256].pack("C").unpack1("C") => 0 >> [257].pack("C").unpack1("C") => 1 ``` This is specified: ```ruby it "encodes the least significant 32 bits of a negative number" do [ [[-0x0000_0021], "\xdf\xff\xff\xff"], [[-0x0000_4321], "\xdf\xbc\xff\xff"], [[-0x0065_4321], "\xdf\xbc\x9a\xff"], [[-0x7865_4321], "\xdf\xbc\x9a\x87"] ].should be_computed_by(:pack, pack_format()) end ``` But not documented in `Array#pack`. I think that in many case this may lead to silent bugs. ### Possible solutions We could have a strict version of `pack`, either `pack(template, strict: true)` or `pack!(template)`. Or alternatively if we think this is never a desired behavior, we could change `pack` to first warn on truncation and later raise. -- https://bugs.ruby-lang.org/ ______________________________________________ ruby-core mailing list -- ruby-core@ml.ruby-lang.org To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/