[Bug libstdc++/104875] libstdc++-v3/src/c++11/codecvt.cc:312:24: warning: left shift count >= width of type

["redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104875

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-03-11
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(c1 << 12) is wrong too, because it loses the high bits.

We should just declare all those variables as char32_t in the first place.

--- a/libstdc++-v3/src/c++11/codecvt.cc
+++ b/libstdc++-v3/src/c++11/codecvt.cc
@@ -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;