On Wed, Jan 10, 2018 at 01:31:22PM -0800, Junio C Hamano wrote:
> > +# Read from stdin into the variable given in $1.
> > +test_read_to_eof () {
> > + # Bash's "read" is sufficiently flexible that we can skip the extra
> > + # process.
> > + if test -n "$BASH_VERSION"
> > + then
> > + # 64k should be enough for anyone...
> > + read -N 65536 -r "$1"
> > + else
> > + # command substitution eats trailing whitespace, so we add
> > + # and then remove a non-whitespace character.
> > + eval "$1=\$(cat; printf x)"
> > + eval "$1=\${$1%x}"
> > + fi
> > +}
>
> Yuck. Hacky but nice.
>
> I think this will make it easier to read but I suspect here text
> would use temporary files and may slow things down a bit? I do not
> know if it is even measurable, though.
Yeah, since I was able to contain the horrible-ness in this function, I
think the overall readability/portability is probably OK. My main
concern was that it would be slower (hence the bash hackery). I applied
the patch below on top to see what kind of impact we could measure
across the whole suite:
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index be8a47d304..6f2e6e7560 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -441,6 +441,15 @@ test_expect_success () {
then
test_read_to_eof test_block
set -- "$1" "$test_block"
+ else
+ # this is obviously a dumb thing to do, but it's just
+ # a performance-testing hack.
+ test_read_to_eof test_block <<EOF
+$2
+EOF
+ # our here-doc hackery added an extra newline
+ set -- "$1" "${test_block%
+}"
fi
test_verify_prereq
export test_prereq
After doing five trial timings each of "make test" on:
- stock git with dash
- this patch with dash (so using "cat" to read the here-doc)
- stock git with bash
- this patch with bash (so using an internal "read")
I couldn't come up with any definitive slowdown.
In the first two, there's a fair bit of run-to-run noise (easily 10%),
and my best run was actually _with_ the patch (by only 3%, but still the
opposite of what you'd expect).
Running the (stock) suite with bash is definitively slower than with
dash (by about 20%). Adding in this patch didn't seem to make it any
slower.
So I dunno. Maybe it's not so crazy an idea.
-Peff
