On 26/04/2017 4:36 PM, Hervé Pagès wrote:
Hi,
I'm running into a case where byte-compilation changes
the semantic of a function. This is with R 3.4.0:
foo <- function(x) { TRUE && x }
foo(c(a=FALSE))
# [1] FALSE # OK
foo(c(a=TRUE))
# [1] TRUE # OK
foo(c(a=FALSE))
# a # ????
# FALSE
The 3rd call returned a result that it different from the 1st
call!
That does look like a bug. Please file a bug report.
After scratching my head for a while, I found out that there
is a lot going on:
1) When calling foo the first 2 times, the function is not
byte-compiled so is behaving as expected.
2) However after the 2nd call, the function gets automatically
compiled. This seems to be a new feature in R 3.4.0 but
you'll have to grep the NEWS file to find out (search for
JIT).
The NEWS file is where we usually report news, so this isn't really that
much of a surprise. If you don't want to read it all at once, you can
see it as it changes on the RSS feed at
http://developer.r-project.org/RSSfeeds.html
The man page for cmpfun/enableJIT nicely explains
the JIT levels but I couldn't find anywhere that the level
is set to 3 by default. I don't even know how one is
supposed to get the current level. Calling enableJIT() to
change the level returns a value, and this value might
look like the previous level, but this is undocumented and
it returns 0 instead of 3 the 1st time I call it anyway.
3) There is some bug in the byte-compiler that seems to make it
treat `&&` like if it were `&` when compiling foo.
It's a bug, but that doesn't describe it completely. TRUE & c(a=TRUE,
b=FALSE) doesn't give the same thing as foo(c(a=TRUE, b=FALSE)).
Duncan Murdoch
Cheers,
H.
> sessionInfo()
R version 3.4.0 (2017-04-21)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 16.04.2 LTS
Matrix products: default
BLAS: /home/biocbuild/bbs-3.5-bioc/R/lib/libRblas.so
LAPACK: /home/biocbuild/bbs-3.5-bioc/R/lib/libRlapack.so
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
[5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=en_US.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] compiler_3.4.0
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