[binutils-gdb] gdb: fix crash when pretty printing anonymous struct with base class
Simon Marchi via Gdb-cvs <[email protected]>
| Newsgroups | gmane.comp.gdb.cvs |
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https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=42cac857bbd7e63776c025af7267ad78db187f8c commit 42cac857bbd7e63776c025af7267ad78db187f8c Author: Simon Marchi <[email protected]> Date: Mon Aug 17 10:59:01 2026 -0400 gdb: fix crash when pretty printing anonymous struct with base class As I was reviewing another patch, I was wondering if we allowed type->name() to be nullptr. The answer is yes, but there are some spots that don't check for nullptr, when they should. Claude came up with a reproducer that inspired the included test case. It is arguably a corner case, but it makes GDB crash. The crash happens when trying to pretty-print (with "set print pretty on") a value of an anonymous struct type that has a base. Given this: struct base { int a; }; struct : base { int b; } v4 = { { 1 }, 2 }; We get: $ ./gdb -nx -q --data-directory=data-directory testsuite/outputs/gdb.cp/anon-struct/anon-struct -ex "with print pretty -- p v4" Reading symbols from testsuite/outputs/gdb.cp/anon-struct/anon-struct... $1 = { <base> = { a = 1 }, /home/smarchi/src/binutils-gdb/gdb/ui-file.h:77:30: runtime error: null pointer passed as argument 1, which is declared to never be null The crash happens here: #4 0x00007ffff600dec8 in __ubsan_handle_nonnull_arg_abort () from /usr/lib/libubsan.so.1 #5 0x00005555637daa35 in ui_file::puts (this=0x7c1ff1c022d0, str=0x0) at /home/smarchi/src/binutils-gdb/gdb/ui-file.h:77 #6 0x0000555566f2b0ab in gdb_puts (linebuffer=0x0, stream=0x7c1ff1c022d0) at /home/smarchi/src/binutils-gdb/gdb/utils.c:1912 #7 0x00005555644e5cd4 in cp_print_value_fields (val=0x7d0ff1c2aa00, stream=0x7c1ff1c022d0, recurse=0, options=0x7bfff094acb0, dont_print_vb=0x0, dont_print_statmem=0) at /home/smarchi/src/binutils-gdb/gdb/cp-valprint.c:213 #8 0x00005555640de708 in c_value_print_struct (val=0x7d0ff1c2aa00, stream=0x7c1ff1c022d0, recurse=0, options=0x7bfff094acb0) at /home/smarchi/src/binutils-gdb/gdb/c-valprint.c:385 #9 0x00005555640df215 in c_value_print_inner (val=0x7d0ff1c2aa00, stream=0x7c1ff1c022d0, recurse=0, options=0x7bfff094acb0) at /home/smarchi/src/binutils-gdb/gdb/c-valprint.c:441 #10 0x000055556563828c in language_defn::value_print_inner (this=0x5555734a0700 <cplus_language_defn>, val=0x7d0ff1c2aa00, stream=0x7c1ff1c022d0, recurse=0, options=0x7bfff094acb0) at /home/smarchi/src/binutils-gdb/gdb/language.c:658 #11 0x0000555566fb7749 in common_val_print (value=0x7d0ff1c2aa00, stream=0x7c1ff1c022d0, recurse=0, options=0x7bfff094aa70, language=0x5555734a0700 <cplus_language_defn>) at /home/smarchi/src/binutils-gdb/gdb/valprint.c:1120 when we try to print the nullptr type name: if (options->prettyformat) { gdb_printf (stream, "\n"); print_spaces (2 + 2 * recurse, stream); gdb_puts ("members of ", stream); gdb_puts (type->name (), stream); gdb_puts (":", stream); } Fix it by using type->safe_name() instead of type->name(). This results in: $1 = { <base> = { a = 1 }, members of <unnamed type>: b = 2 } Claude pointed out that p-valprint.c has more or less the same code, so I changed it there too, but I did not write a test for that one. Change-Id: Ibc4541bf04b7239e31b8401aa86466a6807e89d5 Approved-By: Kevin Buettner <[email protected]> Diff: --- gdb/cp-valprint.c | 2 +- gdb/p-valprint.c | 2 +- gdb/testsuite/gdb.cp/anon-struct-with-base.cc | 49 +++++++++++++++++++ gdb/testsuite/gdb.cp/anon-struct-with-base.exp | 65 ++++++++++++++++++++++++++ 4 files changed, 116 insertions(+), 2 deletions(-) diff --git a/gdb/cp-valprint.c b/gdb/cp-valprint.c index 349a0d6bf9e..d450e90e1e1 100644 --- a/gdb/cp-valprint.c +++ b/gdb/cp-valprint.c @@ -210,7 +210,7 @@ cp_print_value_fields (struct value *val, struct ui_file *stream, gdb_printf (stream, "\n"); print_spaces (2 + 2 * recurse, stream); gdb_puts ("members of ", stream); - gdb_puts (type->name (), stream); + gdb_puts (type->safe_name (), stream); gdb_puts (":", stream); } } diff --git a/gdb/p-valprint.c b/gdb/p-valprint.c index f64c1069b53..2f913a3da15 100644 --- a/gdb/p-valprint.c +++ b/gdb/p-valprint.c @@ -564,7 +564,7 @@ pascal_object_print_value_fields (struct value *val, struct ui_file *stream, gdb_printf (stream, "\n"); print_spaces (2 + 2 * recurse, stream); gdb_puts ("members of ", stream); - gdb_puts (type->name (), stream); + gdb_puts (type->safe_name (), stream); gdb_puts (": ", stream); } } diff --git a/gdb/testsuite/gdb.cp/anon-struct-with-base.cc b/gdb/testsuite/gdb.cp/anon-struct-with-base.cc new file mode 100644 index 00000000000..474473abb66 --- /dev/null +++ b/gdb/testsuite/gdb.cp/anon-struct-with-base.cc @@ -0,0 +1,49 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2026 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 <http://www.gnu.org/licenses/>. */ + +struct base_data +{ + int a; +}; + +struct base_no_data +{ +}; + +struct : base_data +{ + int b; +} v_data_base_data = { { 1 }, 2 }; + +struct : base_data +{ +} v_no_data_base_data = { { 3 } }; + +struct : base_no_data +{ + int c; +} v_data_base_no_data = { {}, 4 }; + +struct : base_no_data +{ +} v_no_data_base_no_data = {}; + +int +main () +{ + return 0; +} diff --git a/gdb/testsuite/gdb.cp/anon-struct-with-base.exp b/gdb/testsuite/gdb.cp/anon-struct-with-base.exp new file mode 100644 index 00000000000..2ff7036198a --- /dev/null +++ b/gdb/testsuite/gdb.cp/anon-struct-with-base.exp @@ -0,0 +1,65 @@ +# Copyright 2026 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 <http://www.gnu.org/licenses/>. + +# Test printing a value whose type is an unnamed struct with a base class. + +standard_testfile .cc + +if {[prepare_for_testing "failed to prepare" $testfile $srcfile \ + {debug c++}]} { + return +} + +gdb_test "with print pretty off -- print v_data_base_data" \ + "$::valnum_re = \{<base_data> = \{a = 1\}, b = 2\}" + +gdb_test "with print pretty off -- print v_no_data_base_data" \ + "$::valnum_re = \{<base_data> = \{a = 3\}, <No data fields>\}" + +gdb_test "with print pretty off -- print v_data_base_no_data" \ + "$::valnum_re = \{<base_no_data> = \{<No data fields>\}, c = 4\}" + +gdb_test "with print pretty off -- print v_no_data_base_no_data" \ + "$::valnum_re = \{<base_no_data> = \{<No data fields>\}, <No data fields>\}" + +gdb_test "with print pretty on -- print v_data_base_data" \ + [multi_line \ + "$::valnum_re = \{" \ + " <base_data> = \{" \ + " a = 1" \ + " \}, " \ + " members of <unnamed type>:" \ + " b = 2" \ + "\}"] + +gdb_test "with print pretty on -- print v_no_data_base_data" \ + [multi_line \ + "$::valnum_re = \{" \ + " <base_data> = \{" \ + " a = 3" \ + " \}, <No data fields>\}"] + +gdb_test "with print pretty on -- print v_data_base_no_data" \ + [multi_line \ + "$::valnum_re = \{" \ + " <base_no_data> = \{<No data fields>\}, " \ + " members of <unnamed type>:" \ + " c = 4" \ + "\}"] + +gdb_test "with print pretty on -- print v_no_data_base_no_data" \ + [multi_line \ + "$::valnum_re = \{" \ + " <base_no_data> = \{<No data fields>\}, <No data fields>\}"]