Expansion of $@ with empty IFS variable

[laurenthuberdeau]

Bug

When IFS='', $@ is expanded with no white space between the elements instead of with white space which breaks word splitting. This simple program shows the issue:

res=0
sum() {
  # implement callee-save calling convention using `set`
  # here, we save the value of $res after the function parameters
  set $@ $res           # $1 $2 $3 are now set
  res=$(($1 + $2))
  echo "$1 + $2 = $res"
  res=$3                # restore the value of $res
}

unset IFS
sum 12 30 # outputs "12 + 30 = 42"

IFS=' '
sum 12 30 # outputs "12 + 30 = 42"

IFS=
sum 12 30 # outputs "1230 + 0 = 1230"

set -u
IFS=
sum 12 30 # fails with "fatal: Undefined variable '2'" on res=$(($1 + $2))

[andychu]

Thanks for finding this and reporting it! I confirmed the bug, and copied the failing test case in

ea5db50

We have to do an overhaul of IFS, since there are a few other bugs there too ...

[andychu]

Note: I tried pnut and hit this

$ ./bootstrap-pnut-sh.sh  --shell ~/git/oilshell/oil/_bin/cxx-opt/osh --fast
Bootstrap with /home/andy/git/oilshell/oil/_bin/cxx-opt/osh
    : $((_$((_heap + result + 1)) = $3))
                                    ^~
build/pnut-sh.sh:195: fatal: Undefined variable '3'
Command exited with non-zero status 1