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* values.c (modify_field): Correct handling of bit-fields that

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don't fit in 32 bits.  Use unsigned operations throughout and
simplify the code a bit.  Document preconditions.
This commit is contained in:
Paul N. Hilfinger
2004-11-01 11:14:38 +00:00
parent 96693b3af8
commit f4e88c8e2c
2 changed files with 18 additions and 15 deletions
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6
gdb/ChangeLog
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@ -1,3 +1,9 @@
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.
2004-10-31 Andrew Cagney <cagney@gnu.org> 2004-10-31 Andrew Cagney <cagney@gnu.org>
* config/pa/tm-linux.h: Delete #undef IN_SOLIB_CALL_TRAMPOLINE. * config/pa/tm-linux.h: Delete #undef IN_SOLIB_CALL_TRAMPOLINE.

27
gdb/values.c
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@ -1070,45 +1070,42 @@ unpack_field_as_long (struct type *type, const char *valaddr, int fieldno)
/* Modify the value of a bitfield. ADDR points to a block of memory in /* 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 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 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 void
modify_field (char *addr, LONGEST fieldval, int bitpos, int bitsize) 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 /* If a negative fieldval fits in the field in question, chop
off the sign extension bits. */ off the sign extension bits. */
if (bitsize < (8 * (int) sizeof (fieldval)) if ((~fieldval & ~(mask >> 1)) == 0)
&& (~fieldval & ~((1 << (bitsize - 1)) - 1)) == 0) fieldval &= mask;
fieldval = fieldval & ((1 << bitsize) - 1);
/* Warn if value is too big to fit in the field in question. */ /* Warn if value is too big to fit in the field in question. */
if (bitsize < (8 * (int) sizeof (fieldval)) if (0 != (fieldval & ~mask))
&& 0 != (fieldval & ~((1 << bitsize) - 1)))
{ {
/* FIXME: would like to include fieldval in the message, but /* FIXME: would like to include fieldval in the message, but
we don't have a sprintf_longest. */ we don't have a sprintf_longest. */
warning ("Value does not fit in %d bits.", bitsize); warning ("Value does not fit in %d bits.", bitsize);
/* Truncate it, otherwise adjoining fields may be corrupted. */ /* 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. */ /* Shifting for bit field depends on endianness of the target machine. */
if (BITS_BIG_ENDIAN) if (BITS_BIG_ENDIAN)
bitpos = sizeof (oword) * 8 - bitpos - bitsize; bitpos = sizeof (oword) * 8 - bitpos - bitsize;
/* Mask out old value, while avoiding shifts >= size of oword */ oword &= ~(mask << bitpos);
if (bitsize < 8 * (int) sizeof (oword))
oword &= ~(((((ULONGEST) 1) << bitsize) - 1) << bitpos);
else
oword &= ~((~(ULONGEST) 0) << bitpos);
oword |= fieldval << 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 */ /* Convert C numbers into newly allocated values */