232 lines
9.4 KiB
Diff
232 lines
9.4 KiB
Diff
http://sourceware.org/ml/gdb-patches/2009-12/msg00394.html
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Subject: [patch] Fix watchpoint-at-epilogue 7.0 regression (s390x)
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Hi,
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attached testcase regressed 6.8->7.0 on some s390x systems.
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At the moment PC is at epilogue (after frame pointer got destroyed and PC is
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still in the calleed function) we must not try any unwinding as it can try to
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unwind a garbage.
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Correct way would be to implement epilogue unwinder (such as
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amd64_epilogue_frame_unwind or i386_epilogue_frame_unwind ones) but it would
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not be so easy on s390x as it would need full prologue-analyzer: After SP gets
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restored there can be various instructions before the last jump - GDB needs to
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interpret the jump to find the register value where it is going to jump to.
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00000048279aa09c <round_and_return>:
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[...]
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48279aa1b8: eb 6f f0 d0 00 04 lmg %r6,%r15,208(%r15)
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48279aa1be: 50 32 10 00 st %r3,0(%r2,%r1) # SP (%r15) is gone hone
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48279aa1c2: b3 74 00 00 lzer %r0
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48279aa1c6: 07 f4 br %r4 # %r4 is the target
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[...]
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Just an easy fix is to be more careful and do not try any unwinding if we find
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PC is in the epilogue (previous instruction modifies SP=%r15).
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It is even a performance optimization and I see no regression risk there.
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The specific s390x error is:
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#0 throw_error (error=MEMORY_ERROR, fmt=0x8042676a "Cannot access memory at address %s") at exceptions.c:415
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#1 in memory_error (status=5, memaddr=0) at corefile.c:220
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#2 in read_memory (memaddr=0, myaddr=0x3ffffc7f7f0 "", len=8) at corefile.c:238
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#3 in read_memory_unsigned_integer (memaddr=0, len=8, byte_order=BFD_ENDIAN_BIG) at corefile.c:321
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#4 in s390_backchain_frame_unwind_cache (this_frame=0x80608958, info=0x80608a08) at s390-tdep.c:1525
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#5 in s390_frame_unwind_cache (this_frame=0x80608958, this_prologue_cache=0x80608970) at s390-tdep.c:1572
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#6 in s390_frame_this_id (this_frame=0x80608958, this_prologue_cache=0x80608970, this_id=0x806089b8) at s390-tdep.c:1583
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#7 in get_frame_id (fi=0x80608958) at frame.c:335
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#8 in frame_find_by_id (id={stack_addr = 4398044824952, code_addr = 2147484952, special_addr = 0, stack_addr_p = 1, code_addr_p = 1, special_addr_p = 0, inline_depth = 0}) at frame.c:587
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#9 in watchpoint_check (p=0x8095bbc0) at breakpoint.c:3203
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#10 in catch_errors (func=0x801262c0 <watchpoint_check>, func_args=0x8095bbc0, errstring=0x80a26410 "Error evaluating expression for watchpoint 3\n", mask=6) at exceptions.c:510
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#11 in bpstat_check_watchpoint (bs=0x8095bbc0) at breakpoint.c:3404
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#12 in bpstat_stop_status (aspace=0x8061fcb0, bp_addr=2147485040, ptid={pid = 17372, lwp = 17372, tid = 0}) at breakpoint.c:3594
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#13 in handle_inferior_event (ecs=0x3ffffc80520) at infrun.c:3588
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I did not analyze why 6.8 did not error out, the GDB code is similar there.
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No regressions on:
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{x86_64,x86_64-m32,i686}-fedora12-linux-gnu (CVS HEAD GDB)
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s390x-rhel48-linux-gnu (CVS HEAD GDB)
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s390-rhel48-linux-gnu (CVS HEAD GDB)
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s390x-rhel54-linux-gnu (Fedora 12 GDB)
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s390-rhel54-linux-gnu (Fedora 12 GDB)
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Thanks,
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Jan
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gdb/
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2009-12-25 Jan Kratochvil <jan.kratochvil@redhat.com>
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* breakpoint.c (watchpoint_check): Check the call
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gdbarch_in_function_epilogue_p before calling frame_find_by_id.
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Extend the comment.
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gdb/testsuite/
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2009-12-25 Jan Kratochvil <jan.kratochvil@redhat.com>
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* gdb.base/watchpoint-cond-gone.exp, gdb.base/watchpoint-cond-gone.c,
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gdb.base/watchpoint-cond-gone-stripped.c: New.
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--- a/gdb/breakpoint.c
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+++ b/gdb/breakpoint.c
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@@ -3200,6 +3200,17 @@ watchpoint_check (void *p)
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struct gdbarch *frame_arch = get_frame_arch (frame);
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CORE_ADDR frame_pc = get_frame_pc (frame);
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+ /* in_function_epilogue_p() returns a non-zero value if we're still
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+ in the function but the stack frame has already been invalidated.
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+ Since we can't rely on the values of local variables after the
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+ stack has been destroyed, we are treating the watchpoint in that
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+ state as `not changed' without further checking. Don't mark
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+ watchpoints as changed if the current frame is in an epilogue -
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+ even if they are in some other frame, our view of the stack
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+ is likely to be wrong and frame_find_by_id could error out. */
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+ if (gdbarch_in_function_epilogue_p (frame_arch, frame_pc))
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+ return WP_VALUE_NOT_CHANGED;
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+
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fr = frame_find_by_id (b->watchpoint_frame);
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within_current_scope = (fr != NULL);
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@@ -3216,17 +3227,6 @@ watchpoint_check (void *p)
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within_current_scope = 0;
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}
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- /* in_function_epilogue_p() returns a non-zero value if we're still
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- in the function but the stack frame has already been invalidated.
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- Since we can't rely on the values of local variables after the
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- stack has been destroyed, we are treating the watchpoint in that
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- state as `not changed' without further checking. Don't mark
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- watchpoints as changed if the current frame is in an epilogue -
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- even if they are in some other frame, our view of the stack
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- is likely to be wrong. */
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- if (gdbarch_in_function_epilogue_p (frame_arch, frame_pc))
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- return WP_VALUE_NOT_CHANGED;
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-
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if (within_current_scope)
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/* If we end up stopping, the current frame will get selected
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in normal_stop. So this call to select_frame won't affect
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--- /dev/null
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+++ b/gdb/testsuite/gdb.base/watchpoint-cond-gone-stripped.c
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@@ -0,0 +1,23 @@
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+/* This testcase is part of GDB, the GNU debugger.
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+
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+ Copyright 2009 Free Software Foundation, Inc.
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+
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+ This program is free software; you can redistribute it and/or modify
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+ it under the terms of the GNU General Public License as published by
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+ the Free Software Foundation; either version 2 of the License, or
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+ (at your option) any later version.
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+
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+ This program is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ GNU General Public License for more details.
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+
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+ You should have received a copy of the GNU General Public License
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+ along with this program; if not, write to the Free Software
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+ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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+
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+void
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+jumper (void (*jumpto) (void))
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+{
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+ (*jumpto) ();
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+}
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--- /dev/null
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+++ b/gdb/testsuite/gdb.base/watchpoint-cond-gone.c
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@@ -0,0 +1,37 @@
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+/* This testcase is part of GDB, the GNU debugger.
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+
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+ Copyright 2009 Free Software Foundation, Inc.
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+
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+ This program is free software; you can redistribute it and/or modify
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+ it under the terms of the GNU General Public License as published by
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+ the Free Software Foundation; either version 2 of the License, or
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+ (at your option) any later version.
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+
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+ This program is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ GNU General Public License for more details.
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+
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+ You should have received a copy of the GNU General Public License
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+ along with this program; if not, write to the Free Software
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+ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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+
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+extern void jumper (void (*jumpto) (void));
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+
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+static void
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+func (void)
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+{
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+ volatile int c;
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+
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+ c = 5;
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+ c = 10; /* watchpoint-here */
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+ c = 20;
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+}
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+
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+int
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+main (void)
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+{
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+ jumper (func);
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+
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+ return 0;
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+}
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--- /dev/null
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+++ b/gdb/testsuite/gdb.base/watchpoint-cond-gone.exp
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@@ -0,0 +1,51 @@
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+# Copyright 2009 Free Software Foundation, Inc.
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+
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+# This program is free software; you can redistribute it and/or modify
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+# it under the terms of the GNU General Public License as published by
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+# the Free Software Foundation; either version 2 of the License, or
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+# (at your option) any later version.
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+#
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+# This program is distributed in the hope that it will be useful,
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+# but WITHOUT ANY WARRANTY; without even the implied warranty of
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+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+# GNU General Public License for more details.
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+#
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+# You should have received a copy of the GNU General Public License
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+# along with this program; if not, write to the Free Software
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+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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+
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+set testfile "watchpoint-cond-gone"
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+set srcfile ${testfile}.c
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+set srcfilestripped ${testfile}-stripped.c
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+set objfilestripped ${objdir}/${subdir}/${testfile}-stripped.o
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+set binfile ${objdir}/${subdir}/${testfile}
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+
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+# We need to generate a function without DWARF to crash older GDB.
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+# Stepping into a dynamic function trampoline or stepping out of MAIN may work
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+# but it is not a reliable FAIL case.
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+
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+if { [gdb_compile "${srcdir}/${subdir}/${srcfilestripped}" "${objfilestripped}" object {}] != ""
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+ || [gdb_compile "${srcdir}/${subdir}/${srcfile} ${objfilestripped}" "${binfile}" executable {debug}] != "" } {
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+ gdb_suppress_entire_file "Testcase compile failed, so all tests in this file will automatically fail."
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+}
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+
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+clean_restart ${testfile}
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+
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+# Problem does not occur otherwise.
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+gdb_test "set can-use-hw-watchpoints 0"
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+
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+if ![runto_main] {
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+ return -1
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+}
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+
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+gdb_breakpoint [gdb_get_line_number "watchpoint-here"]
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+gdb_continue_to_breakpoint "Place to set the watchpoint"
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+
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+# The condition `c == 30' is the subject being tested.
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+gdb_test "watch c if c == 30" "" "Place the watchpoint"
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+
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+# We may stay either in the function itself or only at the first instruction of
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+# its caller depending on the epilogue unwinder (or valid epilogue CFI) presence.
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+gdb_test "finish" \
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+ "Watchpoint .* deleted because the program has left the block in.*which its expression is valid..*in (jumper|func).*" \
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+ "Catch the no longer valid watchpoint"
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