From 4eb591088281a5374a828ea6bf6e25eb33d30e2a Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Fri, 28 Jun 2013 12:36:48 +0000 Subject: [PATCH] [PR tui/14880] Fetch values before comparing their contents. PR tui/14880 shows a reproducer that triggers this assertion: int value_available_contents_eq (const struct value *val1, int offset1, const struct value *val2, int offset2, int length) { int idx1 = 0, idx2 = 0; /* This routine is used by printing routines, where we should already have read the value. Note that we only know whether a value chunk is available if we've tried to read it. */ gdb_assert (!val1->lazy && !val2->lazy); (top-gdb) bt #0 internal_error (file=0x88a26c "../../src/gdb/value.c", line=549, string=0x88a220 "%s: Assertion `%s' failed.") at ../../src/gdb/utils.c:844 #1 0x000000000057b9cd in value_available_contents_eq (val1=0x10fa900, offset1=0, val2=0x10f9e10, offset2=0, length=8) at ../../src/gdb/value.c:549 #2 0x00000000004fd756 in tui_get_register (frame=0xd5c430, data=0x109a548, regnum=0, changedp=0x109a560) at ../../src/gdb/tui/tui-regs.c:736 #3 0x00000000004fd111 in tui_check_register_values (frame=0xd5c430) at ../../src/gdb/tui/tui-regs.c:521 #4 0x0000000000501884 in tui_check_data_values (frame=0xd5c430) at ../../src/gdb/tui/tui-windata.c:234 #5 0x00000000004f976f in tui_selected_frame_level_changed_hook (level=1) at ../../src/gdb/tui/tui-hooks.c:222 #6 0x00000000006f0681 in select_frame (fi=0xd5c430) at ../../src/gdb/frame.c:1490 #7 0x00000000005dd94b in up_silently_base (count_exp=0x0) at ../../src/gdb/stack.c:2268 #8 0x00000000005dd985 in up_command (count_exp=0x0, from_tty=1) at ../../src/gdb/stack.c:2280 #9 0x00000000004dc5cf in do_cfunc (c=0xd3f720, args=0x0, from_tty=1) at ../../src/gdb/cli/cli-decode.c:113 #10 0x00000000004df664 in cmd_func (cmd=0xd3f720, args=0x0, from_tty=1) at ../../src/gdb/cli/cli-decode.c:1888 #11 0x00000000006e43e1 in execute_command (p=0xc7e6c2 "", from_tty=1) at ../../src/gdb/top.c:489 The fix is to fetch the value before comparing the contents. The comment additions to value.h explain why it can't be value_available_contents_eq itself that fetches the contents. Tested on x86_64 Fedora 17. gdb/ 2013-06-28 Pedro Alves PR tui/14880 * tui/tui-regs.c (tui_get_register): Fetch register value contents before checking whether they're available. * value.c (value_available_contents_eq): Change comment. * value.h (value_available_contents_eq): Expand comment. --- gdb/ChangeLog | 8 ++++++++ gdb/tui/tui-regs.c | 7 +++++++ gdb/value.c | 4 +--- gdb/value.h | 7 ++++++- 4 files changed, 22 insertions(+), 4 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 13b705787f..faaaf506eb 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,11 @@ +2013-06-28 Pedro Alves + + PR tui/14880 + * tui/tui-regs.c (tui_get_register): Fetch value contents before + checking if they're available. + * value.c (value_available_contents_eq): Change comment. + * value.h (value_available_contents_eq): Expand comment. + 2013-06-27 Tom Tromey * target.c (find_run_target): Remove. diff --git a/gdb/tui/tui-regs.c b/gdb/tui/tui-regs.c index 7f64a2b3cb..975173a326 100644 --- a/gdb/tui/tui-regs.c +++ b/gdb/tui/tui-regs.c @@ -732,6 +732,13 @@ tui_get_register (struct frame_info *frame, struct gdbarch *gdbarch = get_frame_arch (frame); int size = register_size (gdbarch, regnum); + /* We only know whether a value chunk is available if we've + tried to read it. */ + if (value_lazy (data->value)) + value_fetch_lazy (data->value); + if (value_lazy (old_val)) + value_fetch_lazy (old_val); + if (value_optimized_out (data->value) != value_optimized_out (old_val) || !value_available_contents_eq (data->value, 0, old_val, 0, size)) diff --git a/gdb/value.c b/gdb/value.c index ee3c998303..fae8b98471 100644 --- a/gdb/value.c +++ b/gdb/value.c @@ -543,9 +543,7 @@ value_available_contents_eq (const struct value *val1, int offset1, { int idx1 = 0, idx2 = 0; - /* This routine is used by printing routines, where we should - already have read the value. Note that we only know whether a - value chunk is available if we've tried to read it. */ + /* See function description in value.h. */ gdb_assert (!val1->lazy && !val2->lazy); while (length > 0) diff --git a/gdb/value.h b/gdb/value.h index 4e839d3939..8a66aa48d1 100644 --- a/gdb/value.h +++ b/gdb/value.h @@ -463,7 +463,12 @@ extern void mark_value_bytes_unavailable (struct value *value, value_available_contents_eq(val, 4, val, 12, 2) => 1 value_available_contents_eq(val, 4, val, 12, 4) => 0 value_available_contents_eq(val, 3, val, 4, 4) => 0 -*/ + + We only know whether a value chunk is available if we've tried to + read it. As this routine is used by printing routines, which may + be printing values in the value history, long after the inferior is + gone, it works with const values. Therefore, this routine must not + be called with lazy values. */ extern int value_available_contents_eq (const struct value *val1, int offset1, const struct value *val2, int offset2, -- 2.34.1