Re: [PATCH v3] Add support for the readnever concept

Sergio Durigan Junior
2017-11-29T18:43:03Z

On Wednesday, November 29 2017, Pedro Alves wrote:

> On 11/29/2017 01:21 AM, Sergio Durigan Junior wrote:
>> Changes from v2:
>>
>> - Fixed a few nits pointed by Eli in the docs.
>>
>> - Implemented Pedro's suggestion and moved the logic of readnever out
>> of the "*_build_psymtabs" and into the elf_symfile_read function.
>
> See my comments here:
> https://sourceware.org/ml/gdb-patches/2017-11/msg00766.html

I'll address them, thanks.

>> While implementing the code for the 'symbol-file' command, I noticed a
>> bug in 'symbol_file_command': GDB adds the symbol file before
>> finishing parsing all the options, which means that the position of an
>> option in the command impacts whether it will be considered or not. I
>> changed the code there in order to only add the symbol file after all
>> options have been parsed.
>
> Is this the same as:
>
> https://sourceware.org/ml/gdb-patches/2017-11/msg00656.html
>
> ?

No, it seems like a different issue, even though it's in the same part
of the code.

> Sounds like something that would be better split off to
> a precursor patch.

Sure, I can do that.

>> +++ b/gdb/testsuite/gdb.base/readnever.c
>> @@ -0,0 +1,43 @@
>> +/* Copyright 2016-2017 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/>. */
>> +
>> +#include <stdio.h>
>
> This include isn't necessary.

Removed.

>> +
>> +static void
>> +fun_three (int a, char b, void *c)
>> +{
>> + /* Do nothing. */
>> +}
>> +
>> +static void
>> +fun_two (unsigned int p, const char *y)
>> +{
>> + fun_three ((int) p, '1', (void *) y);
>> +}
>> +
>> +static void
>> +fun_one (int *x)
>> +{
>> + fun_two (10, (const char *) x);
>> +}
>> +
>> +int
>> +main (void)
>> +{
>> + int a = 10;
>> +
>> + fun_one (&a);
>> + return 0;
>> +}
>
>> +# Test invalid combination of flags.
>> +save_vars { GDBFLAGS } {
>> + append GDBFLAGS " --readnever --readnow"
>> + gdb_exit
>> + gdb_spawn_ignore_error
>> +
>> + set test "test readnow and readnever at the same time"
>> + gdb_test_multiple "" $test {
>> + eof {
>> + pass $test
>> + }
>> + }
>
> I had suggested to match GDB's error output before the eof,
> so I'm surprised to see only eof expected?

Wow, I spent a lot of time trying to make this work before and didn't
succeed, but now I think I managed to do it. See below.

>> +}
>> +
>
>> # Default gdb_spawn procedure.
>>
>> -proc default_gdb_spawn { } {
>> +proc default_gdb_spawn { { ignore_error 0 } } {
>> global use_gdb_stub
>> global GDB
>> global INTERNAL_GDBFLAGS GDBFLAGS
>> @@ -1610,11 +1610,12 @@ proc default_gdb_spawn { } {
>> }
>> }
>> set res [remote_spawn host "$GDB $INTERNAL_GDBFLAGS $GDBFLAGS [host_info gdb_opts]"]
>> - if { $res < 0 || $res == "" } {
>> - perror "Spawning $GDB failed."
>> - return 1
>> + if { !$ignore_error } {
>> + if { $res < 0 || $res == "" } {
>> + perror "Spawning $GDB failed."
>> + return 1
>> + }
>> }
>
> Hmm, I think I'm now confused on why this is needed in the first
> place? GDB-the-executable should be starting successfully,
> print some error output, and exit. What error do you see
> here, exactly?

Here's what I see when I try to use gdb_start:

spawn /home/sergio/work/src/git/binutils-gdb/readnever/build-64/gdb/testsuite/../../gdb/gdb -nw -nx -data-directory /home/sergio/work/src/git/binutils-gdb/readnever/build-64/gdb/testsuite/../data-directory --readnever --readnow
/home/sergio/work/src/git/binutils-gdb/readnever/build-64/gdb/testsuite/../../gdb/gdb: '--readnow' and '--readnever' cannot be specified simultaneously
ERROR: : spawn id exp8 not open
while executing
"expect {
-i exp8 -timeout 10
-re "$gdb_prompt $" {
verbose "Setting height to 0." 2
}
timeout {
warning "Couldn't set the height to 0"
..."
("uplevel" body line 1)
invoked from within
"uplevel $body" NONE : spawn id exp8 not open
WARNING: Couldn't set the height to 0
ERROR: : spawn id exp8 not open
while executing
"expect {
-i exp8 -timeout 10
-re "$gdb_prompt $" {
verbose "Setting width to 0." 2
}
timeout {
warning "Couldn't set the width to 0."
}..."
("uplevel" body line 1)
invoked from within
"uplevel $body" NONE : spawn id exp8 not open
WARNING: Couldn't set the width to 0.
ERROR: : spawn id exp8 not open
while executing
"expect {
-i exp8 -timeout 10
-re ".*A problem internal to GDB has been detected" {
fail "$message (GDB internal error)"
gdb_internal_error..."
("uplevel" body line 1)
invoked from within
"uplevel $body" NONE : spawn id exp8 not open
UNRESOLVED: gdb.base/readnever.exp: test readnow and readnever at the same time

It doesn't work because gdb_start does more than spawn GDB; it also sets
height/width and other things. So I tried invoking gdb_spawn directly,
and it worked fine! Thanks for poking me a bit more.

I'll send a v4 with the necessary adjustments.

Thanks,

--
Sergio
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