From 16c3b12f199a7ec99a0b51bd83b66942547bba87 Mon Sep 17 00:00:00 2001 From: Joel Brobecker Date: Mon, 23 Nov 2015 10:02:50 -0800 Subject: [PATCH] error/internal-error printing local variable during "bt full". One of our users reported an internal error using the "bt full" command. In their situation, reproducing involved the following scenario: (gdb) frame 1 (gdb) bt full #0 0xf7783430 in __kernel_vsyscall () No symbol table info available. #1 0xf5550aeb in waitpid () at ../sysdeps/unix/syscall-template.S:81 No locals. [...] #6 0x0fe83139 in xxxx (arg=...) [...some locals printed, and then...] = [...]/dwarf2loc.c:364: internal-error: dwarf_expr_frame_base: Assertion `framefunc != NULL' failed. As shown above, the error happens while GDB is trying to print the value of , which is a local string internally generated by the compiler. For that, it finds that the array lives in memory, and therefore tries to create a struct value for it via: case DWARF_VALUE_MEMORY: { CORE_ADDR address = dwarf_expr_fetch_address (ctx, 0); [...] retval = value_at_lazy (type, address + byte_offset); Unfortunately for us, TYPE happens to be an array whose bounds are dynamic. More precisely, the bounds of our arrays are described in the debugging info as being... <4><2c1985e>: Abbrev Number: 33 (DW_TAG_subrange_type) <2c1985f> DW_AT_type : <0x2c1989c> <2c19863> DW_AT_lower_bound : <0x2c19835> <2c19867> DW_AT_upper_bound : <0x2c19841> ... which are references to a pair of local variables. For instance, the lower bound is a reference to the following DIE <3><2c19835>: Abbrev Number: 32 (DW_TAG_variable) <2c19836> DW_AT_name : [...] <2c1983a> DW_AT_type : <0x2c198b4> <2c1983e> DW_AT_artificial : 1 <2c1983e> DW_AT_location : 2 byte block: 91 58 (DW_OP_fbreg: -40) As a result of the above, value_at_lazy indirectly triggers a resolution of TYPE (via value_from_contents_and_address), which means a resolution of TYPE's bounds, and as seen in the DW_AT_location attribute above for our bounds, computing the bound's location requires the frame (its location expression uses DW_OP_fbreg). Unfortunately for us, value_at_lazy does not get passed a frame, we've lost the relevant frame when we try to resolve the array's bounds. Instead, resolve_dynamic_range gets calls dwarf2_evaluate_property with NULL as the frame: static struct type * resolve_dynamic_range (struct type *dyn_range_type, struct property_addr_info *addr_stack) { [...] if (dwarf2_evaluate_property (prop, NULL, addr_stack, &value)) ^^^^ ... which then handles this by using the selected frame instead: if (frame == NULL && has_stack_frames ()) frame = get_selected_frame (NULL); In our case, the selected frame happens to be frame #1, which is a frame where we have a minimal amount of debugging info, and in particular, no debug info for the function itself. And because of that, when we try to determine the frame's base... static void dwarf_expr_frame_base (void *baton, const gdb_byte **start, size_t * length) { struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; const struct block *bl = get_frame_block (debaton->frame, NULL); [...] framefunc = block_linkage_function (bl); ... framefunc ends up being NULL, which triggers the assert in that same function: gdb_assert (framefunc != NULL); This patches avoids the issue by temporarily setting the selected_frame before printing the locals of each frames. This patch also adds a small testcase, which reproduces the same issue, but with a slightly different outcome: (gdb) bt full #0 0x000000000040049a in opaque_routine () No symbol table info available. #1 0x0000000000400532 in main () at wrong_frame_bt_full-main.c:20 my_table_size = 3 my_table = With this patch, the output becomes: (gdb) bt full [...] my_table = {0, 1, 2} gdb/ChangeLog: * stack.c (print_frame_local_vars): Temporarily set the selected frame to FRAME while printing the frame's local variables. gdb/testsuite/ChangeLog: * gdb.base/wrong_frame_bt_full-main.c: New file. * gdb.base/wrong_frame_bt_full-opaque.c: New file. * gdb.base/wrong_frame_bt_full.exp: New file. --- gdb/ChangeLog | 5 ++ gdb/stack.c | 25 ++++++++-- gdb/testsuite/ChangeLog | 6 +++ gdb/testsuite/gdb.base/wrong_frame_bt_full-main.c | 34 +++++++++++++ .../gdb.base/wrong_frame_bt_full-opaque.c | 22 +++++++++ gdb/testsuite/gdb.base/wrong_frame_bt_full.exp | 55 ++++++++++++++++++++++ 6 files changed, 144 insertions(+), 3 deletions(-) create mode 100644 gdb/testsuite/gdb.base/wrong_frame_bt_full-main.c create mode 100644 gdb/testsuite/gdb.base/wrong_frame_bt_full-opaque.c create mode 100644 gdb/testsuite/gdb.base/wrong_frame_bt_full.exp diff --git a/gdb/ChangeLog b/gdb/ChangeLog index ffcac03..d648e56 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,5 +1,10 @@ 2015-11-23 Joel Brobecker + * stack.c (print_frame_local_vars): Temporarily set the selected + frame to FRAME while printing the frame's local variables. + +2015-11-23 Joel Brobecker + * amd64-windows-tdep.c (amd64_windows_frame_decode_epilogue): Increment PC in while loop skipping "pop reg" instructions. diff --git a/gdb/stack.c b/gdb/stack.c index b825bdf..163b72d 100644 --- a/gdb/stack.c +++ b/gdb/stack.c @@ -2082,6 +2082,7 @@ print_frame_local_vars (struct frame_info *frame, int num_tabs, struct print_variable_and_value_data cb_data; const struct block *block; CORE_ADDR pc; + struct gdb_exception except = exception_none; if (!get_frame_pc_if_available (frame, &pc)) { @@ -2102,9 +2103,27 @@ print_frame_local_vars (struct frame_info *frame, int num_tabs, cb_data.stream = stream; cb_data.values_printed = 0; - iterate_over_block_local_vars (block, - do_print_variable_and_value, - &cb_data); + /* Temporarily change the selected frame to the given FRAME. + This allows routines that rely on the selected frame instead + of being given a frame as parameter to use the correct frame. */ + select_frame (frame); + + TRY + { + iterate_over_block_local_vars (block, + do_print_variable_and_value, + &cb_data); + } + CATCH (ex, RETURN_MASK_ALL) + { + except = ex; + } + END_CATCH + + /* Restore the selected frame, and then rethrow if there was a problem. */ + select_frame (frame_find_by_id (cb_data.frame_id)); + if (except.reason < 0) + throw_exception (except); /* do_print_variable_and_value invalidates FRAME. */ frame = NULL; diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 6518f14..2c59ad8 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,5 +1,11 @@ 2015-11-23 Joel Brobecker + * gdb.base/wrong_frame_bt_full-main.c: New file. + * gdb.base/wrong_frame_bt_full-opaque.c: New file. + * gdb.base/wrong_frame_bt_full.exp: New file. + +2015-11-23 Joel Brobecker + * testsuite/gdb.ada/var_rec_arr.exp: Add "ptype a1(1)" test. 2015-11-20 Jose E. Marchesi diff --git a/gdb/testsuite/gdb.base/wrong_frame_bt_full-main.c b/gdb/testsuite/gdb.base/wrong_frame_bt_full-main.c new file mode 100644 index 0000000..73ab34c --- /dev/null +++ b/gdb/testsuite/gdb.base/wrong_frame_bt_full-main.c @@ -0,0 +1,34 @@ +/* Copyright (C) 2015 Free Software Foundation, Inc. + + This file is part of GDB. + + 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 . */ + +extern void opaque_routine (void); + +int dyn_arr_size = 4; + +int +main (void) +{ + int i; + int my_table_size = dyn_arr_size - 1; + int my_table [my_table_size]; + + for (i = 0; i < my_table_size; i++) + my_table[i] = i; + + opaque_routine (); + return 0; +} diff --git a/gdb/testsuite/gdb.base/wrong_frame_bt_full-opaque.c b/gdb/testsuite/gdb.base/wrong_frame_bt_full-opaque.c new file mode 100644 index 0000000..19b8770 --- /dev/null +++ b/gdb/testsuite/gdb.base/wrong_frame_bt_full-opaque.c @@ -0,0 +1,22 @@ +/* Copyright (C) 2015 Free Software Foundation, Inc. + + This file is part of GDB. + + 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 . */ + +void +opaque_routine (void) +{ + /* Do nothing. */ +} diff --git a/gdb/testsuite/gdb.base/wrong_frame_bt_full.exp b/gdb/testsuite/gdb.base/wrong_frame_bt_full.exp new file mode 100644 index 0000000..863cc1b --- /dev/null +++ b/gdb/testsuite/gdb.base/wrong_frame_bt_full.exp @@ -0,0 +1,55 @@ +# Copyright (C) 2015 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 . + +# Build wrong_frame_bt_full-main using two C files: +# - wrong_frame_bt_full-opaque.c, which needs to be built without +# debugging info; +# - wrong_frame_bt_full-main.c, which needs to be built with +# debugging info. +# This is why we use gdb_compile instead of relying on he usual call +# to prepare_for_testing. + +set main_testfile wrong_frame_bt_full-main +set opaque_testfile wrong_frame_bt_full-opaque + +if {[gdb_compile "${srcdir}/${subdir}/$opaque_testfile.c" \ + $opaque_testfile.o \ + object {}] != ""} { + untested "failed to compile $opaque_testfile.c" + return -1 +} + +if {[gdb_compile \ + [list ${srcdir}/${subdir}/$main_testfile.c $opaque_testfile.o] \ + [standard_output_file ${main_testfile}] \ + executable {debug}] != ""} { + untested "failed to build $main_testfile" + return -1 +} + +clean_restart ${main_testfile} + +if ![runto opaque_routine] { + untested "could not run to opaque_routine" + return -1 +} + +# Make sure that "bt full" command is capable of displaying MY_TABLE +# correctly when frame #0 (the frame which does not have any debugging +# info) is the selected frame. + +gdb_test "bt full" \ + ".*\[\r\n\]+ *my_table = \\{0, 1, 2\\}\[\r\n\]+.*" + -- 2.7.4