https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911
Bug ID: 103911
Summary: std::from_chars shouldn't call isdigit
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: blubban at gmail dot com
Target Milestone: ---
In header <charconv>, function __from_chars_alnum calls std::isdigit().
In addition to looking weird ("everyone" knows ctype is locale dependent and
charconv is not), this can cause trouble in a handful of rare cases.
If another thread concurrently calls setlocale, that's a race condition;
additionally, if the locale contains digits other than '0'..'9', from_chars can
return wrong answer. (For example, some versions of Windows libc think 0xB2,
0xB3 and 0xB9 are the digits ²³¹ in the "us" locale.)
GCC will, by default, replace isdigit with c>='0' && c<='9'; to reproduce the
above, use -fno-builtin or Clang.
(Bonus issue: A comment on that function says it applies to bases 11 to 26.
Shouldn't that be 11 to 36?)
