setlevels() doesn't handle missing or out-of-bounds factor values

I'm aware this is not something you should be doing but I guess crashing is not the best way out.

setattr(factor(c(1:3), levels = c("1", "2")), "levels", c("1", "1"))

System info (where it consistently crashes R).

> version
               _
platform       x86_64-w64-mingw32
arch           x86_64
os             mingw32
crt            ucrt
system         x86_64, mingw32
status
major          4
minor          5.1
year           2025
month          06
day            13
svn rev        88306
language       R
version.string R version 4.5.1 (2025-06-13 ucrt)
nickname       Great Square Root

Thank you for the report! Confirmed on R-devel / gcc -fsanitize=address,undefined / Linux and latest master:

wrappers.c:48:54: runtime error: signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'
Error in data.table::setattr(factor(c(1:3), levels = c("1", "2")), "levels",  : 
  attempt access index 2147483647/2 in STRING_ELT
Execution halted

For your future reports, sessionInfo() would be more informative than just version, even with sensitive parts redacted.

(textproc/R-data.table) Updated 1.16.4 to 1.18.4, Fix build against 4…

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`setlevels()` doesn't handle missing or out-of-bounds factor values #7595

System info (where it consistently crashes R).

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setlevels() doesn't handle missing or out-of-bounds factor values #7595

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System info (where it consistently crashes R).

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aitap commented on Jan 14, 2026

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`setlevels()` doesn't handle missing or out-of-bounds factor values #7595