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From: Tom de Vries <vries@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] [gdb/python] Make gdb.UnwindInfo.add_saved_register more robust Date: Wed, 8 May 2024 12:12:36 +0000 (GMT) [thread overview] Message-ID: <20240508121236.D943B385E836@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2236c5e384de20b0dd6b2fbc964a7269027cb2d9 commit 2236c5e384de20b0dd6b2fbc964a7269027cb2d9 Author: Tom de Vries <tdevries@suse.de> Date: Wed May 8 14:13:11 2024 +0200 [gdb/python] Make gdb.UnwindInfo.add_saved_register more robust On arm-linux, until commit bbb12eb9c84 ("gdb/arm: Remove tpidruro register from non-FreeBSD target descriptions") I ran into: ... FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 5: \ backtrace when the unwind is broken at frame 5 ... What happens is the following: - the TestUnwinder from inline-frame-cycle-unwind.py calls gdb.UnwindInfo.add_saved_register with reg == tpidruro and value "<unavailable>", - pyuw_sniffer calls value->contents ().data () to access the value of the register, which throws an UNAVAILABLE_ERROR, - this causes the TestUnwinder unwinder to fail, after which another unwinder succeeds and returns the correct frame, and - the test-case fails because it's counting on the TestUnwinder to succeed and return an incorrect frame. Fix this by checking for !value::entirely_available as well as valued::optimized_out in unwind_infopy_add_saved_register. Tested on x86_64-linux and arm-linux. Approved-By: Andrew Burgess <aburgess@redhat.com> PR python/31437 Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31437 Diff: --- gdb/python/py-unwind.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/gdb/python/py-unwind.c b/gdb/python/py-unwind.c index a86ccd2c94e..18125e56a46 100644 --- a/gdb/python/py-unwind.c +++ b/gdb/python/py-unwind.c @@ -361,6 +361,18 @@ unwind_infopy_add_saved_register (PyObject *self, PyObject *args, PyObject *kw) return nullptr; } + if (value->optimized_out () || !value->entirely_available ()) + { + /* If we allow this value to be registered here, pyuw_sniffer is going + to run into an exception when trying to access its contents. + Throwing an exception here just puts a burden on the user to + implement the same checks on the user side. We could return False + here and True otherwise, but again that might require changes in user + code. So, handle this with minimal impact for the user, while + improving robustness: silently ignore the register/value pair. */ + Py_RETURN_NONE; + } + gdbpy_ref<> new_value = gdbpy_ref<>::new_reference (pyo_reg_value); bool found = false; for (saved_reg ® : *unwind_info->saved_regs)
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