From e25d6d93c4a0d597da2521c2c38cb1ce6e51feb8 Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Thu, 22 Apr 2021 15:01:28 -0400 Subject: [PATCH] gdb: fix getting range of flexible array member in Python As reported in bug 27757, we get an internal error when doing: $ cat test.c struct foo { int len; int items[]; }; struct foo *p; int main() { return 0; } $ gcc test.c -g -O0 -o test $ ./gdb -q -nx --data-directory=data-directory ./test -ex 'python gdb.parse_and_eval("p").type.target()["items"].type.range()' Reading symbols from ./test... /home/simark/src/binutils-gdb/gdb/gdbtypes.h:435: internal-error: LONGEST dynamic_prop::const_val() const: Assertion `m_kind == PROP_CONST' failed. A problem internal to GDB has been detected, further debugging may prove unreliable. Quit this debugging session? (y or n) This is because the Python code (typy_range) blindly reads the high bound of the type of `items` as a constant value. Since it is a flexible array member, it has no high bound, the property is undefined. Since commit 8c2e4e0689 ("gdb: add accessors to struct dynamic_prop"), the getters check that you are not getting a property value of the wrong kind, so this causes a failed assertion. Fix it by checking if the property is indeed a constant value before accessing it as such. Otherwise, use 0. This restores the previous GDB behavior: because the structure was zero-initialized, this is what was returned before. But now this behavior is explicit and not accidental. Add a test, gdb.python/flexible-array-member.exp, that is derived from gdb.base/flexible-array-member.exp. It tests the same things, but through the Python API. It also specifically tests getting the range from the various kinds of flexible array member types (AFAIK it wasn't possible to do the equivalent through the CLI). gdb/ChangeLog: PR gdb/27757 * python/py-type.c (typy_range): Check that bounds are constant before accessing them as such. * guile/scm-type.c (gdbscm_type_range): Likewise. gdb/testsuite/ChangeLog: PR gdb/27757 * gdb.python/flexible-array-member.c: New test. * gdb.python/flexible-array-member.exp: New test. * gdb.guile/scm-type.exp (test_range): Add test for flexible array member. * gdb.guile/scm-type.c (struct flex_member): New. (main): Use it. Change-Id: Ibef92ee5fd871ecb7c791db2a788f203dff2b841 --- gdb/ChangeLog | 7 ++ gdb/guile/scm-type.c | 11 ++- gdb/python/py-type.c | 11 ++- gdb/testsuite/ChangeLog | 10 +++ gdb/testsuite/gdb.guile/scm-type.c | 12 +++ gdb/testsuite/gdb.guile/scm-type.exp | 12 +++ .../gdb.python/flexible-array-member.c | 70 ++++++++++++++++ .../gdb.python/flexible-array-member.exp | 81 +++++++++++++++++++ 8 files changed, 210 insertions(+), 4 deletions(-) create mode 100644 gdb/testsuite/gdb.python/flexible-array-member.c create mode 100644 gdb/testsuite/gdb.python/flexible-array-member.exp diff --git a/gdb/ChangeLog b/gdb/ChangeLog index d9d0f85135f..67de5ca80bb 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,10 @@ +2021-04-22 Simon Marchi + + PR gdb/27757 + * python/py-type.c (typy_range): Check that bounds are constant + before accessing them as such. + * guile/scm-type.c (gdbscm_type_range): Likewise. + 2021-04-22 Tankut Baris Aktemur * Makefile.in (COMMON_SFILES): Remove continuations.c. diff --git a/gdb/guile/scm-type.c b/gdb/guile/scm-type.c index dd45d8e8b35..11693844edc 100644 --- a/gdb/guile/scm-type.c +++ b/gdb/guile/scm-type.c @@ -823,8 +823,15 @@ gdbscm_type_range (SCM self) case TYPE_CODE_ARRAY: case TYPE_CODE_STRING: case TYPE_CODE_RANGE: - low = type->bounds ()->low.const_val (); - high = type->bounds ()->high.const_val (); + if (type->bounds ()->low.kind () == PROP_CONST) + low = type->bounds ()->low.const_val (); + else + low = 0; + + if (type->bounds ()->high.kind () == PROP_CONST) + high = type->bounds ()->high.const_val (); + else + high = 0; break; } diff --git a/gdb/python/py-type.c b/gdb/python/py-type.c index bf707078841..148e4a6aa3a 100644 --- a/gdb/python/py-type.c +++ b/gdb/python/py-type.c @@ -592,8 +592,15 @@ typy_range (PyObject *self, PyObject *args) case TYPE_CODE_ARRAY: case TYPE_CODE_STRING: case TYPE_CODE_RANGE: - low = type->bounds ()->low.const_val (); - high = type->bounds ()->high.const_val ();; + if (type->bounds ()->low.kind () == PROP_CONST) + low = type->bounds ()->low.const_val (); + else + low = 0; + + if (type->bounds ()->high.kind () == PROP_CONST) + high = type->bounds ()->high.const_val (); + else + high = 0; break; } diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 3099cbacac3..9730658299b 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,13 @@ +2021-04-22 Simon Marchi + + PR gdb/27757 + * gdb.python/flexible-array-member.c: New test. + * gdb.python/flexible-array-member.exp: New test. + * gdb.guile/scm-type.exp (test_range): Add test for flexible + array member. + * gdb.guile/scm-type.c (struct flex_member): New. + (main): Use it. + 2021-04-22 Tom Tromey * gdb.rust/modules.exp: Add checks for syntax errors. diff --git a/gdb/testsuite/gdb.guile/scm-type.c b/gdb/testsuite/gdb.guile/scm-type.c index 782b8fe70cf..64f5f02efed 100644 --- a/gdb/testsuite/gdb.guile/scm-type.c +++ b/gdb/testsuite/gdb.guile/scm-type.c @@ -15,6 +15,8 @@ You should have received a copy of the GNU General Public License along with this program. If not, see . */ +#include + struct s { int a; @@ -53,6 +55,12 @@ enum E struct s vec_data_1 = {1, 1}; struct s vec_data_2 = {1, 2}; +struct flex_member +{ + int n; + int items[]; +}; + int main () { @@ -72,6 +80,10 @@ main () st.b = 5; e = v2; + + struct flex_member *f = (struct flex_member *) malloc (100); + f->items[0] = 111; + f->items[1] = 222; return 0; /* break to inspect struct and array. */ } diff --git a/gdb/testsuite/gdb.guile/scm-type.exp b/gdb/testsuite/gdb.guile/scm-type.exp index 8778cdb36cb..517c99f8369 100644 --- a/gdb/testsuite/gdb.guile/scm-type.exp +++ b/gdb/testsuite/gdb.guile/scm-type.exp @@ -261,6 +261,18 @@ proc test_range {} { "ERROR: .*: Wrong type argument in position 1 \\(expecting ranged type\\): .*" \ "check range for non ranged type" } + + with_test_prefix "on flexible array member" { + gdb_scm_test_silent_cmd "print f" "print value (f)" + gdb_scm_test_silent_cmd "guile (define f (history-ref 0))" \ + "get value (f) from history" + gdb_test "guile (print (type-range (field-type (type-field (value-type (value-dereference f)) \"items\"))))" \ + "= \\(0 0\\)" + gdb_test "guile (print (value-subscript (value-field (value-dereference f) \"items\") 0))" \ + "= 111" + gdb_test "guile (print (value-subscript (value-field (value-dereference f) \"items\") 1))" \ + "= 222" + } } } diff --git a/gdb/testsuite/gdb.python/flexible-array-member.c b/gdb/testsuite/gdb.python/flexible-array-member.c new file mode 100644 index 00000000000..79815e2d38e --- /dev/null +++ b/gdb/testsuite/gdb.python/flexible-array-member.c @@ -0,0 +1,70 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2020-2021 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +#include + +struct no_size +{ + int n; + int items[]; +}; + +struct zero_size +{ + int n; + int items[0]; +}; + +struct zero_size_only +{ + int items[0]; +}; + +struct no_size *ns; +struct zero_size *zs; +struct zero_size_only *zso; + +static void +break_here (void) +{ +} + +int +main (void) +{ + ns = (struct no_size *) malloc (sizeof (*ns) + 3 * sizeof (int)); + zs = (struct zero_size *) malloc (sizeof (*zs) + 3 * sizeof (int)); + zso = (struct zero_size_only *) malloc (sizeof (*zso) + 3 * sizeof (int)); + + ns->n = 3; + ns->items[0] = 101; + ns->items[1] = 102; + ns->items[2] = 103; + + zs->n = 3; + zs->items[0] = 201; + zs->items[1] = 202; + zs->items[2] = 203; + + zso->items[0] = 301; + zso->items[1] = 302; + zso->items[2] = 303; + + break_here (); + + return 0; +} diff --git a/gdb/testsuite/gdb.python/flexible-array-member.exp b/gdb/testsuite/gdb.python/flexible-array-member.exp new file mode 100644 index 00000000000..3739c9a9e5c --- /dev/null +++ b/gdb/testsuite/gdb.python/flexible-array-member.exp @@ -0,0 +1,81 @@ +# Copyright 2020-2021 Free Software Foundation, Inc. + +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + +# Test getting the range of flexible array members in Python. + +standard_testfile + +if { [prepare_for_testing "failed to prepare" \ + ${testfile} ${srcfile}] } { + return +} + +if { ![runto break_here] } { + untested "could not run to break_here" + return +} + +# The various cases are: +# +# - ns: flexible array member with no size +# - zs: flexible array member with size 0 (GNU C extension that predates the +# standardization of the feature, but widely supported) +# - zso: zero-size only, a corner case where the array is the sole member of +# the structure + +gdb_test "python ns = gdb.parse_and_eval('ns').dereference()" +gdb_test "python zs = gdb.parse_and_eval('zs').dereference()" +gdb_test "python zso = gdb.parse_and_eval('zso').dereference()" + +# Print the whole structure. + +gdb_test "python print(ns)" "{n = 3, items = $hex}" +gdb_test "python print(zs)" "{n = 3, items = $hex}" +gdb_test "python print(zso)" "{items = $hex}" + +# Print all items. + +gdb_test "python print(ns\['items'\])" "$hex" +gdb_test "python print(ns\['items'\]\[0\])" "101" +gdb_test "python print(ns\['items'\]\[1\])" "102" +gdb_test "python print(ns\['items'\]\[2\])" "103" + +gdb_test "python print(zs\['items'\])" "$hex" +gdb_test "python print(zs\['items'\]\[0\])" "201" +gdb_test "python print(zs\['items'\]\[1\])" "202" +gdb_test "python print(zs\['items'\]\[2\])" "203" + +gdb_test "python print(zso\['items'\])" "$hex" +gdb_test "python print(zso\['items'\]\[0\])" "301" +gdb_test "python print(zso\['items'\]\[1\])" "302" +gdb_test "python print(zso\['items'\]\[2\])" "303" + +# Check taking the address of array elements (how PR 28675 was originally +# reported). + +gdb_test "python print(ns\['items'\] == ns\['items'\]\[0\].address)" "True" +gdb_test "python print(ns\['items'\]\[0\].address + 1 == ns\['items'\]\[1\].address)" "True" +gdb_test "python print(zs\['items'\] == zs\['items'\]\[0\].address)" "True" +gdb_test "python print(zs\['items'\]\[0\].address + 1 == zs\['items'\]\[1\].address)" "True" +gdb_test "python print(zso\['items'\] == zso\['items'\]\[0\].address)" "True" +gdb_test "python print(zso\['items'\]\[0\].address + 1 == zso\['items'\]\[1\].address)" "True" + +# Verify the range attribute. It looks a bit inconsistent that the high bound +# is sometimes 0, sometimes -1, but that's what GDB produces today, so that's +# what we test. + +gdb_test "python print(ns\['items'\].type.range())" "\\(0, 0\\)" +gdb_test "python print(zs\['items'\].type.range())" "\\(0, -1\\)" +gdb_test "python print(zso\['items'\].type.range())" "\\(0, -1\\)" -- 2.39.5