parse_date() segfaults on invalid format

[sonicdoe]

If a percent sign (%) is misplaced in parse_date()’s format specification, a segmentation fault is raised.

library(readr)
# Note this percent sign  ↓
parse_date("2020-11-17", "%%Y-%m-%d")

With R v4.0.3 and readr v1.4.0:

 *** caught segfault ***
address 0x20, cause 'memory not mapped'

Traceback:
 1: parse_vector_(x, collector, na = na, locale_ = locale, trim_ws = trim_ws)
 2: withCallingHandlers(expr, warning = function(w) if (inherits(w,     classes)) tryInvokeRestart("muffleWarning"))
 3: suppressWarnings(x)
 4: probs(x)
 5: n_problems(x)
 6: warn_problems(parse_vector_(x, collector, na = na, locale_ = locale,     trim_ws = trim_ws))
 7: parse_vector(x, col_date(format), na = na, locale = locale, trim_ws = trim_ws)
 8: parse_date("2020-11-17", "%%Y-%m-%d")

[jimhester]

Thanks for opening the issue, a clear bug that happened in the recent conversion. Should now be fixed.