From 520596f2eb7430dca76d887dc6c39698654af728 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Sat, 17 Oct 2020 00:10:31 +0200 Subject: [PATCH] [gdb/symtab] Handle setting line bp without debug line info When setting a breakpoint on a line in an executable without debug line info, we run into an abort. The problem occurs when calling set_default_source_symtab_and_line, which calls select_source_symtab (0), which is where we try to find the line number for main: ... /* Make the default place to list be the function `main' if one exists. */ block_symbol bsym = lookup_symbol (main_name (), 0, VAR_DOMAIN, 0); if (bsym.symbol != nullptr && SYMBOL_CLASS (bsym.symbol) == LOC_BLOCK) { symtab_and_line sal = find_function_start_sal (bsym.symbol, true); loc->set (sal.symtab, std::max (sal.line - (lines_to_list - 1), 1)); return; } ... However, due to the missing debug line info, find_function_start_sal returns a sal with sal.symtab == 0: ... (gdb) p /x sal $2 = {pspace = 0x1a4a7f0, symtab = 0x0, symbol = 0x1d9e480, section = 0x1d5b398, msymbol = 0x0, line = 0x0, pc = 0x4004ab, end = 0x0, explicit_pc = 0x0, explicit_line = 0x0, is_stmt = 0x0, prob = 0x0, objfile = 0x0} ... which eventually causes an segfault in create_sals_line_offset because self->default_symtab->filename is accessed while self->default_symtab == NULL. Fix this by handling sal.symtab == NULL in select_source_symtab. Tested on x86_64-linux. gdb/ChangeLog: 2020-10-17 Tom de Vries PR symtab/26317 * source.c (select_source_symtab): Handling sal.symtab == NULL for symbol main. gdb/testsuite/ChangeLog: 2020-10-17 Tom de Vries PR symtab/26317 * gdb.dwarf2/dw2-main-no-line-number.exp: New file. --- gdb/ChangeLog | 6 ++ gdb/source.c | 7 +- gdb/testsuite/ChangeLog | 5 ++ .../gdb.dwarf2/dw2-main-no-line-number.exp | 68 +++++++++++++++++++ 4 files changed, 85 insertions(+), 1 deletion(-) create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-main-no-line-number.exp diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 70e1e81a167..9ed649314f5 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2020-10-17 Tom de Vries + + PR symtab/26317 + * source.c (select_source_symtab): Handling sal.symtab == NULL for + symbol main. + 2020-10-14 Tom de Vries PR gdb/26733 diff --git a/gdb/source.c b/gdb/source.c index a73a31f644c..779efa40d9b 100644 --- a/gdb/source.c +++ b/gdb/source.c @@ -306,7 +306,12 @@ select_source_symtab (struct symtab *s) if (bsym.symbol != nullptr && SYMBOL_CLASS (bsym.symbol) == LOC_BLOCK) { symtab_and_line sal = find_function_start_sal (bsym.symbol, true); - loc->set (sal.symtab, std::max (sal.line - (lines_to_list - 1), 1)); + if (sal.symtab == NULL) + /* We couldn't find the location of `main', possibly due to missing + line number info, fall back to line 1 in the corresponding file. */ + loc->set (symbol_symtab (bsym.symbol), 1); + else + loc->set (sal.symtab, std::max (sal.line - (lines_to_list - 1), 1)); return; } diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 50d21cb3027..d5137978a22 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2020-10-17 Tom de Vries + + PR symtab/26317 + * gdb.dwarf2/dw2-main-no-line-number.exp: New file. + 2020-10-17 Tom de Vries * lib/gdb.exp (standard_testfile): Also treat args starting with '-' diff --git a/gdb/testsuite/gdb.dwarf2/dw2-main-no-line-number.exp b/gdb/testsuite/gdb.dwarf2/dw2-main-no-line-number.exp new file mode 100644 index 00000000000..1f62d0ccfc2 --- /dev/null +++ b/gdb/testsuite/gdb.dwarf2/dw2-main-no-line-number.exp @@ -0,0 +1,68 @@ +# Copyright 2020 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 . + +# Setup a main without line number info, and verify that attempting to +# set a breakpoint on a line number doesn't crash gdb. + +load_lib dwarf.exp + +set testname [file rootname [file tail [info script]]] + +# This test can only be run on targets which support DWARF-2 and use gas. +if {![dwarf2_support]} { + verbose "Skipping $testname test." + return 0 +} + +# The .c files use __attribute__. +if [get_compiler_info] { + return -1 +} +if !$gcc_compiled { + verbose "Skipping $testname test." + return 0 +} + +standard_testfile main.c -dw.S + +set asm_file [standard_output_file $srcfile2] +Dwarf::assemble $asm_file { + declare_labels Llines + global srcdir subdir srcfile + + cu {} { + compile_unit { + {language @DW_LANG_C} + {name $srcfile} + } { + subprogram { + {external 1 flag} + {MACRO_AT_func {main}} + } + } + } +} + +if { [prepare_for_testing "failed to prepare" ${testfile} \ + [list $srcfile $asm_file] {nodebug}] } { + return -1 +} + +if ![runto_main] { + return -1 +} + +set breakpoint_at_missing_lineno_set [gdb_breakpoint "1" no-message] +gdb_assert { !$breakpoint_at_missing_lineno_set } -- 2.30.2