From bd454f8baf5382e6ad2869dc077e3d0711a17882 Mon Sep 17 00:00:00 2001 From: Philippe Waroquiers Date: Tue, 12 Nov 2019 20:33:29 +0100 Subject: [PATCH] Fix python gdbpy_breakpoint_object leak. valgrind reports a leak when a breakpoint is created then deleted: ==1313== 40 bytes in 1 blocks are definitely lost in loss record 1,115 of 8,596 ==1313== at 0x4835753: malloc (vg_replace_malloc.c:307) ==1313== by 0x6E05BC: _PyObject_New (object.c:255) ==1313== by 0x470E4B: gdbpy_breakpoint_created(breakpoint*) (py-breakpoint.c:1023) ==1313== by 0x2946D9: operator() (std_function.h:687) ==1313== by 0x2946D9: notify (observable.h:106) ==1313== by 0x2946D9: install_breakpoint(int, std::unique_ptr >&&, int) (breakpoint.c:8136) ==1313== by 0x295BCA: create_breakpoint_sal (breakpoint.c:8878) ==1313== by 0x295BCA: create_breakpoints_sal (breakpoint.c:8919) ==1313== by 0x295BCA: create_breakpoints_sal_default (breakpoint.c:13671) ... The leak is due to a superfluous Py_INCREF when the python object is allocated inside gdbpy_breakpoint_created, when the python object is allocated locally: this object has already a refcount of 1, and the only reference is the reference from the C breakpoint object. The Py_INCREF is however needed when the python object was created from python: the python object was stored in bppy_pending_object, and gdbpy_breakpoint_created creates a new reference to this object. Solve the leak by calling 'Py_INCREF (newbp);' only in the bppy_pending_object case. Regression tested on debian/amd64 natively and under valgrind on centos/amd64. Before the patch, 795 tests have a definite leak. After the patch, 197 have a definite leak. Thanks to Tom, that helped on irc with the python refcount logic. gdb/ChangeLog 2019-11-14 Philippe Waroquiers * python/py-finishbreakpoint.c (gdbpy_breakpoint_created): only call Py_INCREF (newbp) in the bppy_pending_object case. --- gdb/ChangeLog | 5 +++++ gdb/python/py-breakpoint.c | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index be4c5a51f13..8be8efbb417 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2019-11-14 Philippe Waroquiers + + * python/py-finishbreakpoint.c (gdbpy_breakpoint_created): + only call Py_INCREF (newbp) in the bppy_pending_object case. + 2019-11-13 Tom Tromey PR build/25182: diff --git a/gdb/python/py-breakpoint.c b/gdb/python/py-breakpoint.c index 65cb29fdca6..4170737416c 100644 --- a/gdb/python/py-breakpoint.c +++ b/gdb/python/py-breakpoint.c @@ -1017,6 +1017,7 @@ gdbpy_breakpoint_created (struct breakpoint *bp) if (bppy_pending_object) { newbp = bppy_pending_object; + Py_INCREF (newbp); bppy_pending_object = NULL; } else @@ -1027,7 +1028,6 @@ gdbpy_breakpoint_created (struct breakpoint *bp) newbp->bp = bp; newbp->bp->py_bp_object = newbp; newbp->is_finish_bp = 0; - Py_INCREF (newbp); ++bppy_live; } else -- 2.30.2