rc6 won't execute script if it's given as `/dev/stdin` (and won't report error either)

[findepi]

rc5

$ bash -c "graalpython /dev/stdin <<<'print(2**42)'"
Please note: This Python implementation is in the very early stages, and can run little more than basic benchmarks at this point.
4398046511104

$ echo 'print(2**42)' | graalpython /dev/stdin
Please note: This Python implementation is in the very early stages, and can run little more than basic benchmarks at this point.
4398046511104

rc6

$ bash -c "graalpython /dev/stdin <<<'print(2**42)'"
Please note: This Python implementation is in the very early stages, and can run little more than basic benchmarks at this point.
4398046511104

$ echo 'print(2**42)' | graalpython /dev/stdin
Please note: This Python implementation is in the very early stages, and can run little more than basic benchmarks at this point.

i.e. the second call didn't print anything

Repro env

For reproducing, I use isolated docker environment.

FROM debian:stable

ARG GRAAL_VERSION=1.0.0-rc6

RUN apt-get update && \
    apt-get install -y curl && \
    apt-get clean && rm -r "/var/lib/apt/lists"/*

RUN curl -fsSL https://github.com/oracle/graal/releases/download/vm-${GRAAL_VERSION}/graalvm-ce-${GRAAL_VERSION}-linux-amd64.tar.gz -o graalvm.tar.gz
RUN tar xf graalvm.tar.gz
ENV PATH=/graalvm-ce-${GRAAL_VERSION}/bin:/bin:/usr/bin
RUN gu install -c org.graalvm.python

[findepi]

Note: program <<< "text" and echo text | program are not equivalent, at least on my machine.
In the former case, the program can open /dev/stdin/, read it, seek(0), read it again.
In the latter case, seek would fail.

Illustration:

carrot:~$ python -c '
import sys
f = open(sys.argv[1], "r")
print(f.read())
f.seek(0)
print(f.read())
' /dev/stdin <<<"ala ma kota "
ala ma kota

ala ma kota

carrot:~$ echo "ala ma kota " | python -c '
import sys
f = open(sys.argv[1], "r")
print(f.read())
f.seek(0)
print(f.read())
' /dev/stdin
ala ma kota

Traceback (most recent call last):
  File "<string>", line 6, in <module>
IOError: [Errno 29] Illegal seek

My guess would be that graalpython does something like that: reads the input once, seeks back/rewinds (here some error is swallowed), reads again (nothing is read, since we didn't seek). Thus, script to be executed is considered empty.

[findepi]

Also, if you happen to be testing this with docker...
docker run image program <<< "text" doesn't behave like program <<< "text".
In the former case, the input is read by docker client program and probably actively forwarded to the program, so it behaves like echo "text" | program. The latter case's behavior is different, as shown above.

[timfel]

Thanks for the report, nothing comes to mind immediately that would've caused this, we're looking into it.

[timfel]

This will (finally) be fixed with the upcoming rc9

[findepi]

Thanks for fixing this.