Bug #22433: IO#sysread and IO#pread are inconsistent for length 0 and negative numbers

• Status: Open
• Assignee: -
• Target version: -
• Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN

[rhenium (Kazuki Yamaguchi)]

When the length is 0 and an output buffer is given, the buffer is not cleared correctly. [Bug #18421] fixed the same bug for IO#readpartial and IO#read_nonblock, but it omitted IO#sysread and IO#pread:

File.open("/dev/null"){|f|f.read(0,"abc")} #=> ""

# Returns the buffer unmodified
File.open("/dev/null"){|f|f.sysread(0,"abc")} #=> "abc"
File.open("/dev/null"){|f|f.pread(0,0,"abc")} #=> "abc"

These methods should also reject negative lengths:

File.open("/dev/null"){|f|f.read(-1,"abc")} # ArgumentError "negative length -1 given"

# Tries to read (size_t)-1 bytes
File.open("/dev/null"){|f|f.sysread(-1,"abc")} # Errno::EFAULT
File.open("/dev/null"){|f|f.pread(-1,0,"abc")} # Errno::EFAULT

[rhenium (Kazuki Yamaguchi)]

I've opened a GitHub PR: https://github.com/ruby/ruby/pull/19323