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gdb: add asserts in thread code

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Unlike the previous patch, I don't propose that we take this patch into
gdb-10-branch.

This patch adds two asserts, prompted by investigating and fixing the
bug fixed by the previous patch.

The assert in find_thread_ptid would have caught the original issue
before the segfault (I think it's slightly more use friendly).

The assert in add_thread_silent would have made it clear that the
solution proposed in [1] isn't the right one.  The solution ended up
passing nullptr as a target to add_thread.  We don't want that, because
add_thread_silent uses it to look up the inferior to which to add the
thread.  If the target is nullptr, we could find an inferior with the
same pid, but belonging to an unrelated target.  So we always want a
non-nullptr target in add_thread_silent.

gdb/ChangeLog:

	* thread.c (add_thread_silent): Add assert.
	(find_thread_ptid): Add assert.

[1] https://sourceware.org/pipermail/gdb-patches/2021-February/176202.html

Change-Id: Ie593ee45c5eb02235e8e9fbcda612d48ce883852
This commit is contained in:
Simon Marchi
2021-02-22 11:42:03 -05:00
parent de146e1946
commit f53fc42716
2 changed files with 9 additions and 0 deletions
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5
gdb/ChangeLog
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@@ -1,3 +1,8 @@
2021-02-22 Simon Marchi <simon.marchi@polymtl.ca>
* thread.c (add_thread_silent): Add assert.
(find_thread_ptid): Add assert.
2021-02-22 Simon Marchi <simon.marchi@polymtl.ca>
PR gdb/27435

4
gdb/thread.c
View File

@@ -246,6 +246,8 @@ new_thread (struct inferior *inf, ptid_t ptid)
struct thread_info *
add_thread_silent (process_stratum_target *targ, ptid_t ptid)
{
gdb_assert (targ != nullptr);
inferior *inf = find_inferior_ptid (targ, ptid);
/* We may have an old thread with the same id in the thread list.
@@ -535,6 +537,8 @@ find_thread_ptid (process_stratum_target *targ, ptid_t ptid)
struct thread_info *
find_thread_ptid (inferior *inf, ptid_t ptid)
{
gdb_assert (inf != nullptr);
for (thread_info *tp : inf->non_exited_threads ())
if (tp->ptid == ptid)
return tp;