[PATCH 4/5] Fix 64-bit shifts where long only has 32-bit size

[Hannes Domani]

On systems where long has 32-bit size you get these failures:

print 1 << (unsigned long long) 0xffffffffffffffff
Cannot export value 18446744073709551615 as 32-bits unsigned integer (must be between 0 and 4294967295)
(gdb) FAIL: gdb.base/bitshift.exp: lang=c: max-uint64: print 1 << (unsigned long long) 0xffffffffffffffff
print 1 >> (unsigned long long) 0xffffffffffffffff
Cannot export value 18446744073709551615 as 32-bits unsigned integer (must be between 0 and 4294967295)
(gdb) FAIL: gdb.base/bitshift.exp: lang=c: max-uint64: print 1 >> (unsigned long long) 0xffffffffffffffff
print -1 << (unsigned long long) 0xffffffffffffffff
Cannot export value 18446744073709551615 as 32-bits unsigned integer (must be between 0 and 4294967295)
(gdb) FAIL: gdb.base/bitshift.exp: lang=c: max-uint64: print -1 << (unsigned long long) 0xffffffffffffffff
print -1 >> (unsigned long long) 0xffffffffffffffff
Cannot export value 18446744073709551615 as 32-bits unsigned integer (must be between 0 and 4294967295)
(gdb) FAIL: gdb.base/bitshift.exp: lang=c: max-uint64: print -1 >> (unsigned long long) 0xffffffffffffffff

Fixed by changing number-of-bits variable to ULONGEST.
---
 gdb/testsuite/gdb.base/bitshift.exp | 12 ++++++++++++
 gdb/valarith.c                      |  8 ++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/gdb/testsuite/gdb.base/bitshift.exp b/gdb/testsuite/gdb.base/bitshift.exp
index d6e252102d9..cab82e1971e 100644
--- a/gdb/testsuite/gdb.base/bitshift.exp
+++ b/gdb/testsuite/gdb.base/bitshift.exp
@@ -363,6 +363,18 @@ proc test_shifts {} {
 	    test_rshift_tl $lang \
 		"print -1 >> [make_uint64 $lang 0xffffffffffffffff]" " = -1"
 	}
+
+	# Check if shift value isn't silently truncated to 32bit.
+	with_test_prefix "lower-32bit-zero" {
+	    test_lshift_tl $lang \
+		"print 1 << [make_uint64 $lang 0x100000000]" " = 0"
+	    test_rshift_tl $lang \
+		"print 1 >> [make_uint64 $lang 0x100000000]" " = 0"
+	    test_lshift_tl $lang \
+		"print -1 << [make_uint64 $lang 0x100000000]" " = 0"
+	    test_rshift_tl $lang \
+		"print -1 >> [make_uint64 $lang 0x100000000]" " = -1"
+	}
     }
 }
 
diff --git a/gdb/valarith.c b/gdb/valarith.c
index 6160b0e4438..a95d1088133 100644
--- a/gdb/valarith.c
+++ b/gdb/valarith.c
@@ -1086,7 +1086,7 @@ type_length_bits (type *type)
 static bool
 check_valid_shift_count (enum exp_opcode op, type *result_type,
 			 type *shift_count_type, const gdb_mpz &shift_count,
-			 unsigned long &nbits)
+			 ULONGEST &nbits)
 {
   if (!shift_count_type->is_unsigned ())
     {
@@ -1112,7 +1112,7 @@ check_valid_shift_count (enum exp_opcode op, type *result_type,
 	}
     }
 
-  nbits = shift_count.as_integer<unsigned long> ();
+  nbits = shift_count.as_integer<ULONGEST> ();
   if (nbits >= type_length_bits (result_type))
     {
       /* In Go, shifting by large amounts is defined.  Be silent and
@@ -1291,7 +1291,7 @@ scalar_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
 
 	case BINOP_LSH:
 	  {
-	    unsigned long nbits;
+	    ULONGEST nbits;
 	    if (!check_valid_shift_count (op, result_type, type2, v2, nbits))
 	      v = 0;
 	    else
@@ -1301,7 +1301,7 @@ scalar_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
 
 	case BINOP_RSH:
 	  {
-	    unsigned long nbits;
+	    ULONGEST nbits;
 	    if (!check_valid_shift_count (op, result_type, type2, v2, nbits))
 	      {
 		/* Pretend the too-large shift was decomposed in a
-- 
2.35.1