https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66464
Bug ID: 66464
Summary: codecvt_utf16 max_length returning incorrect value
Product: gcc
Version: 5.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: lcarreon at bigpond dot net.au
Target Milestone: ---
I just noticed that codecvt_utf16<char32_t>::max_length() is returning 3.
This appears to be the wrong value because a surrogate pair is composed of 4
bytes therefore max_length() should at least be returning 4.
I'm also wondering whether the BOM should be taken into account. If it so
happens that at the beginning of a UTF-16 string which has a BOM and it so
happens to start with a surrogate pair, 6 bytes have to be consumed to generate
a single UCS-4 character.
Should the same thing be considered with codecvt_utf8<char32_t>::max_length()
which currently returns 4. Taking into account the BOM and the longest UTF-8
character below 0x10FFFF, shouldn't max_length() return 7.
I'm not really sure if the BOM should be taken into account because the
standard's definition for do_max_length() simply says the maximum number of
input characters that needs to be consumed to generate a single output
character.
