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46a4882b3c
An earlier commit made GDB no longer assume no-debug-info functions
return int. This commit gives the same treatment to variables.
Currently, you can end misled by GDB over output like this:
(gdb) p var
$1 = -1
(gdb) p /x var
$2 = 0xffffffff
until you realize that GDB is assuming that the variable is an "int",
because:
(gdb) ptype var
type = <data variable, no debug info>
You may try to fix it by casting, but that doesn't really help:
(gdb) p /x (unsigned long long) var
$3 = 0xffffffffffffffff # incorrect
^^
That's incorrect output, because the variable was defined like this:
uint64_t var = 0x7fffffffffffffff;
^^
What happened is that with the cast, GDB did an int -> 'unsigned long
long' conversion instead of reinterpreting the variable as the cast-to
type. To get at the variable properly you have to reinterpret the
variable's address manually instead, with either:
(gdb) p /x *(unsigned long long *) &var
$4 = 0x7fffffffffffffff
(gdb) p /x {unsigned long long} &var
$5 = 0x7fffffffffffffff
After this commit GDB does it for you. This is what you'll get
instead:
(gdb) p var
'var' has unknown type; cast it to its declared type
(gdb) p /x (unsigned long long) var
$1 = 0x7fffffffffffffff
As in the functions patch, the "compile" machinery doesn't currently
have the cast-to type handy, so it continues assuming no-debug
variables have int type, though now at least it warns.
The change to gdb.cp/m-static.exp deserves an explanation:
- gdb_test "print 'gnu_obj_1::method()::sintvar'" "\\$\[0-9\]+ = 4" \
+ gdb_test "print (int) 'gnu_obj_1::method()::sintvar'" "\\$\[0-9\]+ = 4" \
That's printing the "sintvar" function local static of the
"gnu_obj_1::method()" method.
The problem with that test is that that "'S::method()::static_var'"
syntax doesn't really work in C++ as you'd expect. The way to make it
work correctly currently is to quote the method part, not the whole
expression, like:
(gdb) print 'gnu_obj_1::method()'::sintvar
If you wrap the whole expression in quotes, like in m-static.exp, what
really happens is that the parser considers the whole string as a
symbol name, but there's no debug symbol with that name. However,
local statics have linkage and are given a mangled name that demangles
to the same string as the full expression, so that's what GDB prints.
After this commit, and without the cast, the print in m-static.exp
would error out saying that the variable has unknown type:
(gdb) p 'gnu_obj_1::method()::sintvar'
'gnu_obj_1::method()::sintvar' has unknown type; cast it to its declared type
TBC, if currently (even before this series) you try to print any
function local static variable of type other than int, you'll get
bogus results. You can see that with m-static.cc as is, even.
Printing the "svar" local, which is a boolean (1 byte) still prints as
"int" (4 bytes):
(gdb) p 'gnu_obj_1::method()::svar'
$1 = 1
(gdb) ptype 'gnu_obj_1::method()::svar'
type = <data variable, no debug info>
This probably prints some random bogus value on big endian machines.
If 'svar' was of some aggregate type (etc.) we'd still print it as
int, so the problem would have been more obvious... After this
commit, you'll get instead:
(gdb) p 'gnu_obj_1::method()::svar'
'gnu_obj_1::method()::svar' has unknown type; cast it to its declared type
... so at least GDB is no longer misleading. Making GDB find the real
local static debug symbol is the subject of the following patches. In
the end, it'll all "Just Work".
gdb/ChangeLog:
2017-09-04 Pedro Alves <palves@redhat.com>
* ax-gdb.c: Include "typeprint.h".
(gen_expr_for_cast): New function.
(gen_expr) <OP_CAST, OP_CAST_TYPE>: Use it.
<OP_VAR_VALUE, OP_MSYM_VAR_VALUE>: Error out if the variable's
type is unknown.
* dwarf2read.c (new_symbol_full): Fallback to int instead of
nodebug_data_symbol.
* eval.c: Include "typeprint.h".
(evaluate_subexp_standard) <OP_VAR_VALUE, OP_VAR_MSYM_VALUE>:
Error out if symbol has unknown type.
<UNOP_CAST, UNOP_CAST_TYPE>: Common bits factored out to
evaluate_subexp_for_cast.
(evaluate_subexp_for_address, evaluate_subexp_for_sizeof): Handle
OP_VAR_MSYM_VALUE.
(evaluate_subexp_for_cast): New function.
* gdbtypes.c (init_nodebug_var_type): New function.
(objfile_type): Use it to initialize types of variables with no
debug info.
* typeprint.c (error_unknown_type): New.
* typeprint.h (error_unknown_type): New declaration.
* compile/compile-c-types.c (convert_type_basic): Handle
TYPE_CODE_ERROR; warn and fallback to int for variables with
unknown type.
gdb/testsuite/ChangeLog:
2017-09-04 Pedro Alves <palves@redhat.com>
* gdb.asm/asm-source.exp: Add casts to int.
* gdb.base/nodebug.c (dataglobal8, dataglobal32_1, dataglobal32_2)
(dataglobal64_1, dataglobal64_2): New globals.
* gdb.base/nodebug.exp: Test different expressions involving the
new globals, with print, whatis and ptype. Add casts to int.
* gdb.base/solib-display.exp: Add casts to int.
* gdb.compile/compile-ifunc.exp: Expect warning. Add cast to int.
* gdb.cp/m-static.exp: Add cast to int.
* gdb.dwarf2/dw2-skip-prologue.exp: Add cast to int.
* gdb.threads/tls-nodebug.exp: Check that gdb errors out printing
tls variable with no debug info without a cast. Test with a cast
to int too.
* gdb.trace/entry-values.exp: Add casts.
165 lines
5.1 KiB
Plaintext
165 lines
5.1 KiB
Plaintext
# Copyright 2009-2017 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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# Contributed by Paul Pluzhnikov <ppluzhnikov@google.com>
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#
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# This test case verifies that if a display is active on a variable
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# which belongs in a shared library, and that shared library is
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# reloaded (e.g. due to re-execution of the program), GDB will continue
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# to display it (gdb-6.8 crashed under this scenario).
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# Also test that a display of variable which is currently present in
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# a shared library, but disappears before re-run, doesn't cause GDB
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# difficulties, and that it continues to display other variables.
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# Finally, test that displays which refer to main executable
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# (and thus aren't affected by shared library unloading) are not
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# disabled prematurely.
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if { [skip_shlib_tests] } {
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return 0
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}
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# This test is currently not supported for stub targets, because it uses the
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# start command (through gdb_start_cmd). In theory, it could be changed to
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# use something else (kill + gdb_run_cmd with a manual breakpoint at main).
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# However, when we try that with the native-gdbserver board, we see that the
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# test fails and gdb outputs this upon connection:
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#
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# warning: Unable to display "a_global": No symbol "a_global" in current context.
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# warning: Unable to display "b_global": No symbol "b_global" in current context.
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# warning: Unable to display "c_global": No symbol "c_global" in current context.
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#
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# This is because the initial stop is done before the shared libraries are
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# loaded.
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if { [use_gdb_stub] } {
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return 0
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}
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# Library file.
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set libname "solib-display-lib"
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set srcfile_lib ${srcdir}/${subdir}/${libname}.c
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set binfile_lib [standard_output_file ${libname}.so]
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set lib_flags {}
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# Binary file.
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set testfile "solib-display-main"
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set srcfile ${srcdir}/${subdir}/${testfile}.c
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set executable ${testfile}
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set binfile [standard_output_file ${executable}]
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set bin_flags [list debug shlib=${binfile_lib}]
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if [get_compiler_info] {
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return -1
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}
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# SEP must be last for the possible `unsupported' error path.
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foreach libsepdebug {NO IN SEP} { with_test_prefix "$libsepdebug" {
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set sep_lib_flags $lib_flags
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if {$libsepdebug != "NO"} {
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lappend sep_lib_flags {debug}
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}
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if { [gdb_compile_shlib ${srcfile_lib} ${binfile_lib} $sep_lib_flags] != ""
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|| [gdb_compile ${srcfile} ${binfile} executable $bin_flags] != "" } {
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untested "failed to compile"
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return -1
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}
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if {$libsepdebug == "SEP"} {
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if {[gdb_gnu_strip_debug $binfile_lib] != 0} {
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unsupported "could not split debug of $binfile_lib."
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return
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} else {
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pass "split solib"
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}
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}
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clean_restart $executable
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if ![runto_main] then {
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fail "can't run to main"
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return 0
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}
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gdb_test "display (int) a_global" "1: \\(int\\) a_global = 41"
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gdb_test "display (int) b_global" "2: \\(int\\) b_global = 42"
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gdb_test "display (int) c_global" "3: \\(int\\) c_global = 43"
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if { [gdb_start_cmd] < 0 } {
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fail "can't run to main (2)"
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continue
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}
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gdb_test "" [multi_line \
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"1: \\(int\\) a_global = 41" \
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"2: \\(int\\) b_global = 42" \
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"3: \\(int\\) c_global = 43" \
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] "after rerun"
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# Now rebuild the library without b_global
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if { [gdb_compile_shlib ${srcfile_lib} ${binfile_lib} \
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"$sep_lib_flags additional_flags=-DNO_B_GLOBAL"] != ""} {
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fail "can't rebuild $binfile_lib"
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}
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if {$libsepdebug == "SEP"} {
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set test "split solib second time"
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if {[gdb_gnu_strip_debug $binfile_lib] != 0} {
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fail $test
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continue
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} else {
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pass $test
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}
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}
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if { [gdb_start_cmd] < 0 } {
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fail "can't run to main (3)"
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continue
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}
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gdb_test "" [multi_line \
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"1: \\(int\\) a_global = 41" \
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"warning: .*b_global.*" \
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"3: \\(int\\) c_global = 43" \
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] "after rerun (2)"
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# Now verify that displays which are not in the shared library
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# are not cleared permaturely.
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gdb_test "break [gdb_get_line_number "break here" ${testfile}.c]" \
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".*Breakpoint.* at .*"
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gdb_test "continue"
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gdb_test "display main_global" "4: main_global = 44"
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gdb_test "display a_local" "5: a_local = 45"
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gdb_test "display a_static" "6: a_static = 46"
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if { [gdb_start_cmd] < 0 } {
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fail "can't run to main (4)"
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continue
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}
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gdb_test "" "6: a_static = 46\\r\\n4: main_global = 44\\r\\n.*"
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gdb_test "break [gdb_get_line_number "break here" ${testfile}.c]" \
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".*Breakpoint.* at .*"
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gdb_test "continue" [multi_line \
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"4: main_global = 44" \
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"5: a_local = 45" \
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"6: a_static = 46" \
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]
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}}
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