[Rd] byte-compiler bug

[Hervé Pagès]

On 04/26/2017 04:46 PM, luke-tierney at uiowa.edu wrote:
> Thanks for the report. Fixed in R_devel with r72631; I'll port to
> R-patched later today or tomorrow.

Thanks!

>
> The default setting and how to get the current settings are documented
> in the Details section of the enableJIT help page at the end of the
> paragraph for enableJIT.

Indeed. Sorry for missing that (I was playing with several versions
of R and probably looked at the enableJIT man page in the wrong R).

H.

>
> Best,
>
> luke
>
> On Wed, 26 Apr 2017, 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!
>>
>> 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
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