[Rd] byte-compiler bug

[Hervé Pagès]

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!

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 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.

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

-- 
Hervé Pagès

Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M1-B514
P.O. Box 19024
Seattle, WA 98109-1024

E-mail: hpages at fredhutch.org
Phone:  (206) 667-5791
Fax:    (206) 667-1319