bumping lots of columns in fread makes R crash

[richierocks]

When fread has to bump many columns to a different data type, R can crash. This dataset with 10k rows and 40 columns makes R consistently crash:

library(data.table)

# Create a character column that is mostly empty,
# so it gets bumped.
x <- character(1e4)
x[9994] <- "+"
# For very powerful machines, you might need to  
# increase the number of rows a little.
dfr <- as.data.frame(
  replicate(40, x, simplify = FALSE)
)
write.table(dfr, "test.txt", quote = FALSE)

fread("test.txt")

[dwaggott]

This one is really frustrating. The majority of my large datasets are sparse and crash R using fread.

[mattdowle]

Fixed in v1.9.4 on CRAN. Have added this one into the same item - thanks.

Fixed seg fault in sparse data files when bumping to character, #796 and #722. Thanks to Adam Kennedy and Richard Cotton for the detailed reproducible reports.