Bug #19597: Process.argv0 returns the same mutable String

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN

[andrykonchin (Andrew Konchin)]

Process.argv0 returns a name of the script being executed. But it seems it's always the same object, that can be modified and this change will be visible to the consequent Process.argv0 calls.

It makes sense to return a frozen String that cannot be modified.

$0 initial value equals a value returned by Process.argv0 so $0 by default also could be a frozen String.

Example:

puts "Object id:"
p Process.argv0.object_id
p Process.argv0.object_id

puts "Value before modification:"
p Process.argv0
Process.argv0.upcase!

puts "Value after modification:"
p Process.argv0

puts "$0 after modification:"
p $0

It will output:

Object id:
60
60
Value before modification:
"argv0.rb"
Value after modification:
"ARGV0.RB"
$0 after modification:
"ARGV0.RB"

[andrykonchin (Andrew Konchin)]

• Description updated (diff)

[nobu (Nobuyoshi Nakada)]

https://github.com/ruby/ruby/pull/7709

[nobu (Nobuyoshi Nakada)]

I found $0 had been frozen till 1.9.

$ ruby1.9 -e 'p $0.upcase!; p $0; system("ps #$$")'
-e:1:in `upcase!': can't modify frozen String (RuntimeError)
	from -e:1:in `<main>'

I'm not sure why/when it changed, yet.

[nobu (Nobuyoshi Nakada)]

Once assigned to $0, it is frozen.

$ ruby -v -e '$0 = "test"; p $0; $0.upcase!'
ruby 3.3.0dev (2023-05-05T14:01:50Z master 40438fc4d3) [x86_64-darwin22]
"test"
-e:1:in `upcase!': can't modify frozen String: "test" (FrozenError)
	from -e:1:in `<main>'

So I'd say that only the first $0 is not frozen is a bug.

[nobu (Nobuyoshi Nakada)]

It's 8c9a453f2d8a.
ruby_set_script_name makes an unfrozen copy.

[nobu (Nobuyoshi Nakada)]

• Tracker changed from Misc to Bug
• Backport set to 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset git|2d9bc3efe57fe0ec1a8171340c950fb98ca8c8f2.

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[Bug #19597] Freeze script name