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Re: [RFA] Setting long long bitfields
- From: Paul Hilfinger <hilfingr at gnat dot com>
- To: cagney at gnu dot org
- Cc: gdb-patches at sources dot redhat dot com
- Date: Mon, 1 Nov 2004 06:17:49 -0500 (EST)
- Subject: Re: [RFA] Setting long long bitfields
- References: <20041031090847.2E303F2985@nile.gnat.com> <41852B2B.6030305@gnu.org>
I have committed the revised version of this patch, below.
Paul Hilfinger
2004-11-01 Paul N. Hilfinger <Hilfinger@gnat.com>
* values.c (modify_field): Correct handling of bit-fields that
don't fit in 32 bits. Use unsigned operations throughout and
simplify the code a bit. Document preconditions.
Index: gdb/values.c
===================================================================
RCS file: /cvs/src/src/gdb/values.c,v
retrieving revision 1.71
diff -u -p -r1.71 values.c
--- gdb/values.c 28 Jul 2004 02:46:24 -0000 1.71
+++ gdb/values.c 1 Nov 2004 10:42:29 -0000
@@ -1070,45 +1070,42 @@ unpack_field_as_long (struct type *type,
/* Modify the value of a bitfield. ADDR points to a block of memory in
target byte order; the bitfield starts in the byte pointed to. FIELDVAL
is the desired value of the field, in host byte order. BITPOS and BITSIZE
- indicate which bits (in target bit order) comprise the bitfield. */
+ indicate which bits (in target bit order) comprise the bitfield.
+ Requires 0 < BITSIZE <= lbits, 0 <= BITPOS+BITSIZE <= lbits, and
+ 0 <= BITPOS, where lbits is the size of a LONGEST in bits. */
void
modify_field (char *addr, LONGEST fieldval, int bitpos, int bitsize)
{
- LONGEST oword;
+ ULONGEST oword;
+ ULONGEST mask = (ULONGEST) -1 >> (8 * sizeof (ULONGEST) - bitsize);
/* If a negative fieldval fits in the field in question, chop
off the sign extension bits. */
- if (bitsize < (8 * (int) sizeof (fieldval))
- && (~fieldval & ~((1 << (bitsize - 1)) - 1)) == 0)
- fieldval = fieldval & ((1 << bitsize) - 1);
+ if ((~fieldval & ~(mask >> 1)) == 0)
+ fieldval &= mask;
/* Warn if value is too big to fit in the field in question. */
- if (bitsize < (8 * (int) sizeof (fieldval))
- && 0 != (fieldval & ~((1 << bitsize) - 1)))
+ if (0 != (fieldval & ~mask))
{
/* FIXME: would like to include fieldval in the message, but
we don't have a sprintf_longest. */
warning ("Value does not fit in %d bits.", bitsize);
/* Truncate it, otherwise adjoining fields may be corrupted. */
- fieldval = fieldval & ((1 << bitsize) - 1);
+ fieldval &= mask;
}
- oword = extract_signed_integer (addr, sizeof oword);
+ oword = extract_unsigned_integer (addr, sizeof oword);
/* Shifting for bit field depends on endianness of the target machine. */
if (BITS_BIG_ENDIAN)
bitpos = sizeof (oword) * 8 - bitpos - bitsize;
- /* Mask out old value, while avoiding shifts >= size of oword */
- if (bitsize < 8 * (int) sizeof (oword))
- oword &= ~(((((ULONGEST) 1) << bitsize) - 1) << bitpos);
- else
- oword &= ~((~(ULONGEST) 0) << bitpos);
+ oword &= ~(mask << bitpos);
oword |= fieldval << bitpos;
- store_signed_integer (addr, sizeof oword, oword);
+ store_unsigned_integer (addr, sizeof oword, oword);
}
/* Convert C numbers into newly allocated values */