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libstdc++: Fix reading UTF-8 characters for 16-bit targets [PR104875]

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The current code in read_utf8_code_point assumes that integer promotion
will create a 32-bit int, but that's not true for 16-bit targets like
msp430 and avr. This changes the intermediate variables used for each
octet from unsigned char to char32_t, so that (c << N) works correctly
when N > 8.

libstdc++-v3/ChangeLog:

	PR libstdc++/104875
	* src/c++11/codecvt.cc (read_utf8_code_point): Use char32_t to
	hold octets that will be left-shifted.
This commit is contained in:
Jonathan Wakely 2022-03-11 14:52:38 +00:00
parent 67a1cb2ad1
commit 8f7b7c1495
1 changed files with 7 additions and 7 deletions
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14
libstdc++-v3/src/c++11/codecvt.cc
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@ -254,7 +254,7 @@ namespace
const size_t avail = from.size();
if (avail == 0)
return incomplete_mb_character;
unsigned char c1 = from[0];
char32_t c1 = (unsigned char) from[0];
// https://en.wikipedia.org/wiki/UTF-8#Sample_code
if (c1 < 0x80)
{
@ -267,7 +267,7 @@ namespace
{
if (avail < 2)
return incomplete_mb_character;
unsigned char c2 = from[1];
char32_t c2 = (unsigned char) from[1];
if ((c2 & 0xC0) != 0x80)
return invalid_mb_sequence;
char32_t c = (c1 << 6) + c2 - 0x3080;
@ -279,12 +279,12 @@ namespace
{
if (avail < 3)
return incomplete_mb_character;
unsigned char c2 = from[1];
char32_t c2 = (unsigned char) from[1];
if ((c2 & 0xC0) != 0x80)
return invalid_mb_sequence;
if (c1 == 0xE0 && c2 < 0xA0) // overlong
return invalid_mb_sequence;
unsigned char c3 = from[2];
char32_t c3 = (unsigned char) from[2];
if ((c3 & 0xC0) != 0x80)
return invalid_mb_sequence;
char32_t c = (c1 << 12) + (c2 << 6) + c3 - 0xE2080;
@ -296,17 +296,17 @@ namespace
{
if (avail < 4)
return incomplete_mb_character;
unsigned char c2 = from[1];
char32_t c2 = (unsigned char) from[1];
if ((c2 & 0xC0) != 0x80)
return invalid_mb_sequence;
if (c1 == 0xF0 && c2 < 0x90) // overlong
return invalid_mb_sequence;
if (c1 == 0xF4 && c2 >= 0x90) // > U+10FFFF
return invalid_mb_sequence;
unsigned char c3 = from[2];
char32_t c3 = (unsigned char) from[2];
if ((c3 & 0xC0) != 0x80)
return invalid_mb_sequence;
unsigned char c4 = from[3];
char32_t c4 = (unsigned char) from[3];
if ((c4 & 0xC0) != 0x80)
return invalid_mb_sequence;
char32_t c = (c1 << 18) + (c2 << 12) + (c3 << 6) + c4 - 0x3C82080;