[Rd] loop compilation problem

[Lukas Stadler]

Hi!

We’ve seen a problem with the compiler in specific cases of matrix updates:

> { m <- matrix(1:4, 2) ; z <- 0; for(i in 1) { m[z <- z + 1,z <- z + 1] <- 99; } ; m }
     [,1] [,2]
[1,]    1    3
[2,]    2   99

Here, it modifies element [2,2], which is unexpected.
It behaves correct without the loop:

> { m <- matrix(1:4, 2) ; z <- 0; m[z <- z + 1,z <- z + 1] <- 99 ; m }
     [,1] [,2]
[1,]    1   99
[2,]    2    4

… and without the jit:

> enableJIT(0)
[1] 3
> { m <- matrix(1:4, 2) ; z <- 0; for(i in 1) { m[z <- z + 1,z <- z + 1] <- 99; } ; m }
     [,1] [,2]
[1,]    1   99
[2,]    2    4

I checked with "R Under development (unstable) (2017-08-23 r73116)”, and the problem is still there.

- Lukas