[RFA] Setting long long bitfields
Andrew Cagney
cagney@gnu.org
Sun Oct 31 18:13:00 GMT 2004
Paul Hilfinger wrote:
> The patch below fixes a small problem with assignments in GDB to
> long long bitfields (which, while not a standard part of C are provided
> by GCC). The existing code computes the correct mask for zeroing out
> the old value, but uses int computations in the code that truncates
> the field value and tests whether it fits. Bit-fields that don't fit
> in an int are rare in C code, but they do crop up more in Ada, which
> allows considerably more aggressive packing. I have included a draft of
> a new set of testsuite files (in C) that tickle the problem.
Looks under patch, nope no testcase, looking forward to it :-)
Yes, ok.
One possible tweak, several of us have an aversion to "?:", it would be
nice if it wasn't there :-)
Andrew
> Paul Hilfinger
>
> 2004-10-31 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 consistently and
> simplify the code a bit.
>
> 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 31 Oct 2004 08:26:17 -0000
> @@ -1075,40 +1075,36 @@ unpack_field_as_long (struct type *type,
> void
> modify_field (char *addr, LONGEST fieldval, int bitpos, int bitsize)
> {
> - LONGEST oword;
> + ULONGEST oword;
> + ULONGEST mask = (bitsize == 8 * (int) sizeof (ULONGEST)
> + ? ~(ULONGEST) 0 : ((ULONGEST) 1 << bitsize) - 1);
>
> /* 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 */
> Index: current-public.116/gdb/testsuite/gdb.base/bitfields2.exp
> --- current-public.116/gdb/testsuite/gdb.base/bitfields2.exp Sun, 31 Oct 2004 01:11:22 -0700 hilfingr ()
> +++ merge.238(w)/gdb/testsuite/gdb.base/bitfields2.exp Sun, 31 Oct 2004 00:51:17 -0700 hilfingr (GdbPub/q/c/36_bitfields2 1.1 644)
> @@ -0,0 +1,325 @@
> +# Copyright 1992, 1994, 1995, 1997, 2004 Free Software Foundation, Inc.
> +
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 2 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program; if not, write to the Free Software
> +# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
> +
> +# Please email any bugs, comments, and/or additions to this file to:
> +# bug-gdb@prep.ai.mit.edu
> +
> +# This file was adapted from bitfields.exp by Paul Hilfinger
> +# (Hilfinger@gnat.com)
> +
> +#
> +# Tests for bit-fields that do not fit in type (unsigned) int, but do fit
> +# in type (unsigned) long long. We perform essentially the same tests as
> +# in bitfields.c, which considers only bit-fields that are <= 9 bits long.
> +#
> +
> +if $tracelevel then {
> + strace $tracelevel
> +}
> +
> +set prms_id 0
> +set bug_id 0
> +
> +set testfile "bitfields2"
> +set srcfile ${testfile}.c
> +set binfile ${objdir}/${subdir}/${testfile}
> +if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
> + gdb_suppress_entire_file "Testcase compile failed, so all tests in this file will automatically fail."
> +}
> +
> +set no_signed 0
> +
> +#
> +# Test bitfield locating and uniqueness.
> +# For each member, set that member to 1 and verify that the member (and only
> +# that member) is 1, then reset it back to 0.
> +#
> +
> +proc bitfield_uniqueness {} {
> + global decimal
> + global hex
> + global gdb_prompt
> + global srcfile
> +
> + if { ! [runto break1] } {
> + gdb_suppress_tests;
> + }
> +
> + if [gdb_test "print flags" ".*u1 = 0, u2 = 0, u3 = 0, s1 = 1, s2 = 0, s3 = 0.*" "bitfield uniqueness (s1)"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "cont" "Break.*break1 \\(\\) at .*$srcfile:$decimal.*" "continuing to break1 #1"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "print flags" ".*u1 = 1, u2 = 0, u3 = 0, s1 = 0, s2 = 0, s3 = 0.*" "bitfield uniqueness (u1)"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "cont" "Break.*break1 \\(\\) at .*$srcfile:$decimal.*" "continuing to break1 #2"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "print flags" ".*u1 = 0, u2 = 0, u3 = 0, s1 = 0, s2 = 1, s3 = 0.*" "bitfield uniqueness (s2)"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "cont" "Break.*break1 \\(\\) at .*$srcfile:$decimal.*" "continuing to break1 #3"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "print flags" ".*u1 = 0, u2 = 1, u3 = 0, s1 = 0, s2 = 0, s3 = 0.*" "bitfield uniqueness (u2)"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "cont" "Break.*break1 \\(\\) at .*$srcfile:$decimal.*" "continuing to break1 #4"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "print flags" ".*u1 = 0, u2 = 0, u3 = 0, s1 = 0, s2 = 0, s3 = 1.*" "bitfield uniqueness (s3)"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "cont" "Break.*break1 \\(\\) at .*$srcfile:$decimal.*" "continuing to break1 #5"] {
> + gdb_suppress_tests;
> + }
> + if [gdb_test "print flags" ".*u1 = 0, u2 = 0, u3 = 1, s1 = 0, s2 = 0, s3 = 0.*" "bitfield uniqueness (u3)"] {
> + gdb_suppress_tests
> + }
> + gdb_stop_suppressing_tests;
> +}
> +
> +
> +#
> +# Test bitfield containment.
> +# Fill alternating fields with all 1's and verify that none of the bits
> +# "bleed over" to the other fields.
> +#
> +
> +proc bitfield_containment {} {
> + global decimal
> + global hex
> + global gdb_prompt
> + global srcfile
> +
> + delete_breakpoints
> +
> + if { ![runto break2] } {
> + gdb_suppress_tests
> + }
> +
> + # If program is compiled with Sun CC, signed fields print out as their
> + # actual sizes; if compiled with gcc, they print out as 0xffffffff.
> + if [gdb_test "print/x flags" "= {u1 = 0x7fff, u2 = 0x0, u3 = 0xffff, s1 = 0x0, s2 = 0x(1ffffffff|f*), s3 = 0x0}" "bitfield containment #1"] {
> + gdb_suppress_tests
> + }
> +
> + if [gdb_test "cont" "Break.*break2 \\(\\) at .*$srcfile:$decimal.*" "continuing to break2"] {
> + gdb_suppress_tests
> + }
> +
> + if [gdb_test "print/x flags" "= {u1 = 0x0, u2 = 0x1ffffffff, u3 = 0x0, s1 = 0x(7fff|f*), s2 = 0x0, s3 = 0xf*}" "bitfield containment #2"] {
> + gdb_suppress_tests
> + }
> + gdb_stop_suppressing_tests;
> +}
> +
> +# Test unsigned bitfields for unsignedness and range.
> +# Fill the unsigned fields with the maximum positive value and verify that
> +# the values are printed correctly.
> +
> +proc bitfield_unsignedness {} {
> + global decimal
> + global hex
> + global gdb_prompt
> + global srcfile
> +
> + delete_breakpoints
> +
> + if { ![runto break3] } {
> + gdb_suppress_tests
> + }
> +
> + if [gdb_test "print flags" ".*u1 = 32767, u2 = 8589934591, u3 = 65535, s1 = 0, s2 = 0, s3 = 0.*" "unsigned bitfield ranges"] {
> + gdb_suppress_tests
> + }
> + gdb_stop_suppressing_tests;
> +}
> +
> +#
> +# Test signed bitfields for signedness and range.
> +# Fill the signed fields with the maximum positive value, then the maximally
> +# negative value, then -1, and verify in each case that the values are
> +# printed correctly.
> +#
> +
> +proc bitfield_signedness {} {
> + global decimal
> + global hex
> + global gdb_prompt
> + global srcfile
> + global no_signed
> +
> + delete_breakpoints
> +
> + if { ! [runto break4] } {
> + gdb_suppress_tests
> + }
> +
> + if [gdb_test "print flags" "= {.*u1 = 0, u2 = 0, u3 = 0, s1 = 16383, s2 = 4294967295, s3 = 32767.*}" "signed bitfields, max positive values"] {
> + gdb_suppress_tests
> + }
> +
> + if [gdb_test "cont" "Break.*break4 \\(\\) at .*$srcfile:$decimal.*" "continuing to break4 #1"] {
> + gdb_suppress_tests
> + }
> +
> + # Determine if the target has signed bitfields so we can xfail the
> + # the signed bitfield tests if it doesn't.
> + set no_signed 1
> + send_gdb "print i\n"
> + gdb_expect {
> + -re ".* = -32768.*$gdb_prompt $" {
> + set no_signed 0
> + pass "determining signed-ness of bitfields"
> + }
> + -re ".* = 32768.*$gdb_prompt $" {
> + pass "determining signed-ness of bitfields"
> + setup_xfail "*-*-*"
> + }
> + -re ".*$gdb_prompt $" {
> + fail "determining signed-ness of bitfields"
> + gdb_suppress_tests
> + }
> + default {
> + fail "determining signed-ness of bitfields" ;
> + gdb_suppress_tests;
> + }
> + }
> +
> + if [gdb_test "print flags" "u1 = 0, u2 = 0, u3 = 0, s1 = -16384, s2 = -4294967296, s3 = -32768.*" "signed bitfields, max negative values"] {
> + gdb_suppress_tests
> + }
> +
> + if [gdb_test "cont" "Break.*break4 \\(\\) at .*$srcfile:$decimal.*" "continuing to break4 #2"] {
> + gdb_suppress_tests
> + }
> +
> + if [gdb_test "print flags" "u1 = 0, u2 = 0, u3 = 0, s1 = -1, s2 = -1, s3 = -1.*" "signed bitfields with -1"] {
> + gdb_suppress_tests
> + }
> + # Hmmmm???
> + gdb_stop_suppressing_tests;
> +}
> +
> +
> +# Test setting of long long bit fields from within GDB.
> +
> +proc bitfield_set {} {
> + global decimal
> + global hex
> + global gdb_prompt
> + global srcfile
> + global no_signed
> +
> + delete_breakpoints
> +
> + if { ! [runto break5] } {
> + gdb_suppress_tests
> + }
> +
> + set big_set_failed 0
> + set test "set long long unsigned bitfield"
> + gdb_test_multiple "print flags.u2 = 0x100000000" $test {
> + -re "warning: Value does not fit.*$gdb_prompt $" {
> + fail "$test"
> + gdb_suppress_tests
> + }
> + -re "= 4294967296.*$gdb_prompt $" {
> + pass "$test"
> + }
> + }
> +
> + set test "set long long signed bitfield positive"
> + gdb_test_multiple "print flags.s2 = 0x80000000" $test {
> + -re "warning: Value does not fit.*$gdb_prompt $" {
> + fail "$test"
> + gdb_suppress_tests
> + }
> + -re "= 2147483648.*$gdb_prompt $" {
> + pass "$test"
> + }
> + }
> +
> + if [gdb_test "print flags" "u1 = 0, u2 = 4294967296, u3 = 0, s1 = 0, s2 = 2147483648, s3 = 0.*" "long long bitfield values after set"] {
> + gdb_suppress_tests
> + }
> +
> + if $no_signed then {
> + setup_xfail "*-*-*"
> + }
> + set test "set long long signed bitfield negative"
> + gdb_test_multiple "print flags.s2 = -1" $test {
> + -re "warning: Value does not fit.*$gdb_prompt $" {
> + fail "$test"
> + gdb_suppress_tests
> + }
> + -re "= -1.*$gdb_prompt $" {
> + pass "$test"
> + }
> + }
> +
> + if $no_signed then {
> + setup_xfail "*-*-*"
> + }
> + if [gdb_test "print flags" "u1 = 0, u2 = 4294967296, u3 = 0, s1 = 0, s2 = -1, s3 = 0.*" "long long bitfield values after set negative"] {
> + gdb_suppress_tests
> + }
> + gdb_stop_suppressing_tests;
> +}
> +
> +gdb_start
> +gdb_reinitialize_dir $srcdir/$subdir
> +gdb_load ${binfile}
> +
> +send_gdb "set print sevenbit-strings\n" ; gdb_expect -re "$gdb_prompt $"
> +
> +bitfield_uniqueness
> +if [istarget "mips-idt-*"] then {
> + # Restart because IDT/SIM runs out of file descriptors.
> + gdb_exit
> + gdb_start
> + gdb_reinitialize_dir $srcdir/$subdir
> + gdb_load ${binfile}
> +}
> +bitfield_containment
> +if [istarget "mips-idt-*"] then {
> + # Restart because IDT/SIM runs out of file descriptors.
> + gdb_exit
> + gdb_start
> + gdb_reinitialize_dir $srcdir/$subdir
> + gdb_load ${binfile}
> +}
> +bitfield_unsignedness
> +if [istarget "mips-idt-*"] then {
> + # Restart because IDT/SIM runs out of file descriptors.
> + gdb_exit
> + gdb_start
> + gdb_reinitialize_dir $srcdir/$subdir
> + gdb_load ${binfile}
> +}
> +bitfield_signedness
> +if [istarget "mips-idt-*"] then {
> + # Restart because IDT/SIM runs out of file descriptors.
> + gdb_exit
> + gdb_start
> + gdb_reinitialize_dir $srcdir/$subdir
> + gdb_load ${binfile}
> +}
> +bitfield_set
> +
> Index: current-public.116/gdb/testsuite/gdb.base/bitfields2.c
> --- current-public.116/gdb/testsuite/gdb.base/bitfields2.c Sun, 31 Oct 2004 01:11:22 -0700 hilfingr ()
> +++ merge.238(w)/gdb/testsuite/gdb.base/bitfields2.c Sun, 31 Oct 2004 00:51:17 -0700 hilfingr (GdbPub/q/c/37_bitfields2 1.1 644)
> @@ -0,0 +1,162 @@
> +/* Test program to test bit field operations on bit fields of large
> + integer types. */
> +
> +/* This file is expected to fail to compile if the type long long int
> + is not supported, but in that case it is irrelevant. */
> +
> +#if !defined(__STDC__) && !defined(__cplusplus)
> +#define signed /**/
> +#endif
> +
> +struct fields
> +{
> + unsigned long long u1 : 15;
> + unsigned long long u2 : 33;
> + unsigned long long u3 : 16;
> + signed long long s1 : 15;
> + signed long long s2 : 33;
> + signed long long s3 : 16;
> +} flags;
> +
> +void break1 ()
> +{
> +}
> +
> +void break2 ()
> +{
> +}
> +
> +void break3 ()
> +{
> +}
> +
> +void break4 ()
> +{
> +}
> +
> +void break5 ()
> +{
> +}
> +
> +void break6 ()
> +{
> +}
> +
> +void break7 ()
> +{
> +}
> +
> +void break8 ()
> +{
> +}
> +
> +void break9 ()
> +{
> +}
> +
> +void break10 ()
> +{
> +}
> +
> +/* This is used by bitfields.exp to determine if the target understands
> + signed bitfields. */
> +int i;
> +
> +int main ()
> +{
> + /* For each member, set that member to 1, allow gdb to verify that the
> + member (and only that member) is 1, and then reset it back to 0. */
> +
> +#ifdef usestubs
> + set_debug_traps();
> + breakpoint();
> +#endif
> + flags.s1 = 1;
> + break1 ();
> + flags.s1 = 0;
> +
> + flags.u1 = 1;
> + break1 ();
> + flags.u1 = 0;
> +
> + flags.s2 = 1;
> + break1 ();
> + flags.s2 = 0;
> +
> + flags.u2 = 1;
> + break1 ();
> + flags.u2 = 0;
> +
> + flags.s3 = 1;
> + break1 ();
> + flags.s3 = 0;
> +
> + flags.u3 = 1;
> + break1 ();
> + flags.u3 = 0;
> +
> + /* Fill alternating fields with all 1's and verify that none of the bits
> + "bleed over" to the other fields. */
> +
> + flags.u1 = 0x7FFF;
> + flags.u3 = 0xFFFF;
> + flags.s2 = -1LL;
> + break2 ();
> + flags.u1 = 0;
> + flags.u3 = 0;
> + flags.s2 = 0;
> +
> + flags.u2 = 0x1FFFFFFFFLL;
> + flags.s1 = -1;
> + flags.s3 = -1;
> + break2 ();
> +
> + flags.u2 = 0;
> + flags.s1 = 0;
> + flags.s3 = 0;
> +
> + /* Fill the unsigned fields with the maximum positive value and verify
> + that the values are printed correctly. */
> +
> + flags.u1 = 0x7FFF;
> + flags.u2 = 0x1FFFFFFFFLL;
> + flags.u3 = 0xFFFF;
> + break3 ();
> + flags.u1 = 0;
> + flags.u2 = 0;
> + flags.u3 = 0;
> +
> + /* Fill the signed fields with the maximum positive value, then the maximally
> + negative value, then -1, and verify in each case that the values are
> + printed correctly. */
> +
> + /* Maximum positive values */
> + flags.s1 = 0x3FFF;
> + flags.s2 = 0xFFFFFFFFLL;
> + flags.s3 = 0x7FFF;
> + break4 ();
> +
> + /* Maximally negative values */
> + flags.s1 = -0x4000;
> + flags.s2 = -0x100000000LL;
> + flags.s3 = -0x8000;
> +
> + /* Extract bitfield value so that bitfield.exp can check if the target
> + understands signed bitfields. */
> + i = flags.s3;
> + break4 ();
> +
> + /* -1 */
> + flags.s1 = -1;
> + flags.s2 = -1;
> + flags.s3 = -1;
> + break4 ();
> +
> + flags.s1 = 0;
> + flags.s2 = 0;
> + flags.s3 = 0;
> +
> + break5 ();
> +
> + return 0;
> +}
>
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