[gcc r13-4369] libstdc++: Fix _Hash_bytes for I16LP32 targets [PR107885]

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:7b79fa930917da735f02b4f6911dfbb0a91f9714

commit r13-4369-g7b79fa930917da735f02b4f6911dfbb0a91f9714
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Nov 28 10:52:23 2022 +0000

    libstdc++: Fix _Hash_bytes for I16LP32 targets [PR107885]
    
    For H8/300 size_t is 32 bits wide, but (unsigned char)buf[2] << 16
    promotes to int which is only 16 bits wide. The shift is then undefined.
    This fixes it by converting to size_t before shifting.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/107885
            * libsupc++/hash_bytes.cc (_Hash_bytes): Convert to size_t
            instead of implicit integer promotion to 16 bits.

Diff:
---
 libstdc++-v3/libsupc++/hash_bytes.cc | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/libsupc++/hash_bytes.cc b/libstdc++-v3/libsupc++/hash_bytes.cc
index ffdd04f7602..67e2dbb1a0f 100644
--- a/libstdc++-v3/libsupc++/hash_bytes.cc
+++ b/libstdc++-v3/libsupc++/hash_bytes.cc
@@ -90,17 +90,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	len -= 4;
       }
 
+    size_t k;
     // Handle the last few bytes of the input array.
     switch(len)
       {
       case 3:
-	hash ^= static_cast<unsigned char>(buf[2]) << 16;
+	k = static_cast<unsigned char>(buf[2]);
+	hash ^= k << 16;
 	[[gnu::fallthrough]];
       case 2:
-	hash ^= static_cast<unsigned char>(buf[1]) << 8;
+	k = static_cast<unsigned char>(buf[1]);
+	hash ^= k << 8;
 	[[gnu::fallthrough]];
       case 1:
-	hash ^= static_cast<unsigned char>(buf[0]);
+	k = static_cast<unsigned char>(buf[0]);
+	hash ^= k;
 	hash *= m;
       };