2018-01-01 12:43:02 +08:00
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/* Copyright (C) 2011-2018 Free Software Foundation, Inc.
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2017-06-07 21:21:40 +08:00
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This file is part of GDB.
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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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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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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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#include "defs.h"
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#include "gdb_regex.h"
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Introduce gdb::byte_vector, add allocator that default-initializes
In some cases we've been replacing heap-allocated gdb_byte buffers
managed with xmalloc/make_cleanup(xfree) with gdb::vector<gdb_byte>.
That usually pessimizes the code a little bit because std::vector
value-initializes elements (which for gdb_byte means
zero-initialization), while if you're creating a temporary buffer,
you're most certaintly going to fill it in with some data. An
alternative is to use
unique_ptr<gdb_byte[]> buf (new gdb_byte[size]);
but it looks like that's not very popular.
Recently, a use of obstacks in dwarf2read.c was replaced with
std::vector<gdb_byte> and that as well introduced a pessimization for
always memsetting the buffer when it's garanteed that the zeros will
be overwritten immediately. (see dwarf2read.c change in this patch to
find it.)
So here's a different take at addressing this issue "by design":
#1 - Introduce default_init_allocator<T>
I.e., a custom allocator that does default construction using default
initialization, meaning, no more zero initialization. That's the
default_init_allocation<T> class added in this patch.
See "Notes" at
<http://en.cppreference.com/w/cpp/container/vector/resize>.
#2 - Introduce def_vector<T>
I.e., a convenience typedef, because typing the allocator is annoying:
using def_vector<T> = std::vector<T, gdb::default_init_allocator<T>>;
#3 - Introduce byte_vector
Because gdb_byte vectors will be the common thing, add a convenience
"byte_vector" typedef:
using byte_vector = def_vector<gdb_byte>;
which is really the same as:
std::vector<gdb_byte, gdb::default_init_allocator<gdb_byte>>;
The intent then is to make "gdb::byte_vector" be the go-to for dynamic
byte buffers. So the less friction, the better.
#4 - Adjust current code to use it.
To set the example going forward. Replace std::vector uses and also
unique_ptr<byte[]> uses.
One nice thing is that with this allocator, for changes like these:
-std::unique_ptr<byte[]> buf (new gdb_byte[some_size]);
+gdb::byte_vector buf (some_size);
fill_with_data (buf.data (), buf.size ());
the generated code is the same as before. I.e., the compiler
de-structures the vector and gets rid of the unused "reserved vs size"
related fields.
The other nice thing is that it's easier to write
gdb::byte_vector buf (size);
than
std::unique_ptr<gdb_byte[]> buf (new gdb_byte[size]);
or even (C++14):
auto buf = std::make_unique<gdb_byte[]> (size); // zero-initializes...
#5 - Suggest s/std::vector<gdb_byte>/gdb::byte_vector/ going forward.
Note that this commit actually fixes a couple of bugs where the current
code is incorrectly using "std::vector::reserve(new_size)" and then
accessing the vector's internal buffer beyond the vector's size: see
dwarf2loc.c and charset.c. That's undefined behavior and may trigger
debug mode assertion failures. With default_init_allocator,
"resize()" behaves like "reserve()" performance wise, in that it
leaves new elements with unspecified values, but, it does that safely
without triggering undefined behavior when you access those values.
gdb/ChangeLog:
2017-06-14 Pedro Alves <palves@redhat.com>
* ada-lang.c: Include "common/byte-vector.h".
(ada_value_primitive_packed_val): Use gdb::byte_vector.
* charset.c (wchar_iterator::iterate): Resize the vector instead
of reserving it.
* common/byte-vector.h: Include "common/def-vector.h".
(wchar_iterator::m_out): Now a gdb::def_vector<gdb_wchar_t>.
* cli/cli-dump.c: Include "common/byte-vector.h".
(dump_memory_to_file, restore_binary_file): Use gdb::byte_vector.
* common/byte-vector.h: New file.
* common/def-vector.h: New file.
* common/default-init-alloc.h: New file.
* dwarf2loc.c: Include "common/byte-vector.h".
(rw_pieced_value): Use gdb::byte_vector, and resize the vector
instead of reserving it.
* dwarf2read.c: Include "common/byte-vector.h".
(data_buf::m_vec): Now a gdb::byte_vector.
* gdb_regex.c: Include "common/def-vector.h".
(compiled_regex::compiled_regex): Use gdb::def_vector<char>.
* mi/mi-main.c: Include "common/byte-vector.h".
(mi_cmd_data_read_memory): Use gdb::byte_vector.
* printcmd.c: Include "common/byte-vector.h".
(print_scalar_formatted): Use gdb::byte_vector.
* valprint.c: Include "common/byte-vector.h".
(maybe_negate_by_bytes, print_decimal_chars): Use
gdb::byte_vector.
2017-06-14 18:08:52 +08:00
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#include "common/def-vector.h"
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2017-06-07 21:21:40 +08:00
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compiled_regex::compiled_regex (const char *regex, int cflags,
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const char *message)
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{
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gdb_assert (regex != NULL);
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gdb_assert (message != NULL);
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int code = regcomp (&m_pattern, regex, cflags);
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if (code != 0)
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{
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size_t length = regerror (code, &m_pattern, NULL, 0);
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Introduce gdb::byte_vector, add allocator that default-initializes
In some cases we've been replacing heap-allocated gdb_byte buffers
managed with xmalloc/make_cleanup(xfree) with gdb::vector<gdb_byte>.
That usually pessimizes the code a little bit because std::vector
value-initializes elements (which for gdb_byte means
zero-initialization), while if you're creating a temporary buffer,
you're most certaintly going to fill it in with some data. An
alternative is to use
unique_ptr<gdb_byte[]> buf (new gdb_byte[size]);
but it looks like that's not very popular.
Recently, a use of obstacks in dwarf2read.c was replaced with
std::vector<gdb_byte> and that as well introduced a pessimization for
always memsetting the buffer when it's garanteed that the zeros will
be overwritten immediately. (see dwarf2read.c change in this patch to
find it.)
So here's a different take at addressing this issue "by design":
#1 - Introduce default_init_allocator<T>
I.e., a custom allocator that does default construction using default
initialization, meaning, no more zero initialization. That's the
default_init_allocation<T> class added in this patch.
See "Notes" at
<http://en.cppreference.com/w/cpp/container/vector/resize>.
#2 - Introduce def_vector<T>
I.e., a convenience typedef, because typing the allocator is annoying:
using def_vector<T> = std::vector<T, gdb::default_init_allocator<T>>;
#3 - Introduce byte_vector
Because gdb_byte vectors will be the common thing, add a convenience
"byte_vector" typedef:
using byte_vector = def_vector<gdb_byte>;
which is really the same as:
std::vector<gdb_byte, gdb::default_init_allocator<gdb_byte>>;
The intent then is to make "gdb::byte_vector" be the go-to for dynamic
byte buffers. So the less friction, the better.
#4 - Adjust current code to use it.
To set the example going forward. Replace std::vector uses and also
unique_ptr<byte[]> uses.
One nice thing is that with this allocator, for changes like these:
-std::unique_ptr<byte[]> buf (new gdb_byte[some_size]);
+gdb::byte_vector buf (some_size);
fill_with_data (buf.data (), buf.size ());
the generated code is the same as before. I.e., the compiler
de-structures the vector and gets rid of the unused "reserved vs size"
related fields.
The other nice thing is that it's easier to write
gdb::byte_vector buf (size);
than
std::unique_ptr<gdb_byte[]> buf (new gdb_byte[size]);
or even (C++14):
auto buf = std::make_unique<gdb_byte[]> (size); // zero-initializes...
#5 - Suggest s/std::vector<gdb_byte>/gdb::byte_vector/ going forward.
Note that this commit actually fixes a couple of bugs where the current
code is incorrectly using "std::vector::reserve(new_size)" and then
accessing the vector's internal buffer beyond the vector's size: see
dwarf2loc.c and charset.c. That's undefined behavior and may trigger
debug mode assertion failures. With default_init_allocator,
"resize()" behaves like "reserve()" performance wise, in that it
leaves new elements with unspecified values, but, it does that safely
without triggering undefined behavior when you access those values.
gdb/ChangeLog:
2017-06-14 Pedro Alves <palves@redhat.com>
* ada-lang.c: Include "common/byte-vector.h".
(ada_value_primitive_packed_val): Use gdb::byte_vector.
* charset.c (wchar_iterator::iterate): Resize the vector instead
of reserving it.
* common/byte-vector.h: Include "common/def-vector.h".
(wchar_iterator::m_out): Now a gdb::def_vector<gdb_wchar_t>.
* cli/cli-dump.c: Include "common/byte-vector.h".
(dump_memory_to_file, restore_binary_file): Use gdb::byte_vector.
* common/byte-vector.h: New file.
* common/def-vector.h: New file.
* common/default-init-alloc.h: New file.
* dwarf2loc.c: Include "common/byte-vector.h".
(rw_pieced_value): Use gdb::byte_vector, and resize the vector
instead of reserving it.
* dwarf2read.c: Include "common/byte-vector.h".
(data_buf::m_vec): Now a gdb::byte_vector.
* gdb_regex.c: Include "common/def-vector.h".
(compiled_regex::compiled_regex): Use gdb::def_vector<char>.
* mi/mi-main.c: Include "common/byte-vector.h".
(mi_cmd_data_read_memory): Use gdb::byte_vector.
* printcmd.c: Include "common/byte-vector.h".
(print_scalar_formatted): Use gdb::byte_vector.
* valprint.c: Include "common/byte-vector.h".
(maybe_negate_by_bytes, print_decimal_chars): Use
gdb::byte_vector.
2017-06-14 18:08:52 +08:00
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gdb::def_vector<char> err (length);
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2017-06-07 21:21:40 +08:00
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|
Introduce gdb::byte_vector, add allocator that default-initializes
In some cases we've been replacing heap-allocated gdb_byte buffers
managed with xmalloc/make_cleanup(xfree) with gdb::vector<gdb_byte>.
That usually pessimizes the code a little bit because std::vector
value-initializes elements (which for gdb_byte means
zero-initialization), while if you're creating a temporary buffer,
you're most certaintly going to fill it in with some data. An
alternative is to use
unique_ptr<gdb_byte[]> buf (new gdb_byte[size]);
but it looks like that's not very popular.
Recently, a use of obstacks in dwarf2read.c was replaced with
std::vector<gdb_byte> and that as well introduced a pessimization for
always memsetting the buffer when it's garanteed that the zeros will
be overwritten immediately. (see dwarf2read.c change in this patch to
find it.)
So here's a different take at addressing this issue "by design":
#1 - Introduce default_init_allocator<T>
I.e., a custom allocator that does default construction using default
initialization, meaning, no more zero initialization. That's the
default_init_allocation<T> class added in this patch.
See "Notes" at
<http://en.cppreference.com/w/cpp/container/vector/resize>.
#2 - Introduce def_vector<T>
I.e., a convenience typedef, because typing the allocator is annoying:
using def_vector<T> = std::vector<T, gdb::default_init_allocator<T>>;
#3 - Introduce byte_vector
Because gdb_byte vectors will be the common thing, add a convenience
"byte_vector" typedef:
using byte_vector = def_vector<gdb_byte>;
which is really the same as:
std::vector<gdb_byte, gdb::default_init_allocator<gdb_byte>>;
The intent then is to make "gdb::byte_vector" be the go-to for dynamic
byte buffers. So the less friction, the better.
#4 - Adjust current code to use it.
To set the example going forward. Replace std::vector uses and also
unique_ptr<byte[]> uses.
One nice thing is that with this allocator, for changes like these:
-std::unique_ptr<byte[]> buf (new gdb_byte[some_size]);
+gdb::byte_vector buf (some_size);
fill_with_data (buf.data (), buf.size ());
the generated code is the same as before. I.e., the compiler
de-structures the vector and gets rid of the unused "reserved vs size"
related fields.
The other nice thing is that it's easier to write
gdb::byte_vector buf (size);
than
std::unique_ptr<gdb_byte[]> buf (new gdb_byte[size]);
or even (C++14):
auto buf = std::make_unique<gdb_byte[]> (size); // zero-initializes...
#5 - Suggest s/std::vector<gdb_byte>/gdb::byte_vector/ going forward.
Note that this commit actually fixes a couple of bugs where the current
code is incorrectly using "std::vector::reserve(new_size)" and then
accessing the vector's internal buffer beyond the vector's size: see
dwarf2loc.c and charset.c. That's undefined behavior and may trigger
debug mode assertion failures. With default_init_allocator,
"resize()" behaves like "reserve()" performance wise, in that it
leaves new elements with unspecified values, but, it does that safely
without triggering undefined behavior when you access those values.
gdb/ChangeLog:
2017-06-14 Pedro Alves <palves@redhat.com>
* ada-lang.c: Include "common/byte-vector.h".
(ada_value_primitive_packed_val): Use gdb::byte_vector.
* charset.c (wchar_iterator::iterate): Resize the vector instead
of reserving it.
* common/byte-vector.h: Include "common/def-vector.h".
(wchar_iterator::m_out): Now a gdb::def_vector<gdb_wchar_t>.
* cli/cli-dump.c: Include "common/byte-vector.h".
(dump_memory_to_file, restore_binary_file): Use gdb::byte_vector.
* common/byte-vector.h: New file.
* common/def-vector.h: New file.
* common/default-init-alloc.h: New file.
* dwarf2loc.c: Include "common/byte-vector.h".
(rw_pieced_value): Use gdb::byte_vector, and resize the vector
instead of reserving it.
* dwarf2read.c: Include "common/byte-vector.h".
(data_buf::m_vec): Now a gdb::byte_vector.
* gdb_regex.c: Include "common/def-vector.h".
(compiled_regex::compiled_regex): Use gdb::def_vector<char>.
* mi/mi-main.c: Include "common/byte-vector.h".
(mi_cmd_data_read_memory): Use gdb::byte_vector.
* printcmd.c: Include "common/byte-vector.h".
(print_scalar_formatted): Use gdb::byte_vector.
* valprint.c: Include "common/byte-vector.h".
(maybe_negate_by_bytes, print_decimal_chars): Use
gdb::byte_vector.
2017-06-14 18:08:52 +08:00
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regerror (code, &m_pattern, err.data (), length);
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error (("%s: %s"), message, err.data ());
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2017-06-07 21:21:40 +08:00
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}
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}
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compiled_regex::~compiled_regex ()
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{
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regfree (&m_pattern);
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}
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int
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compiled_regex::exec (const char *string, size_t nmatch,
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regmatch_t pmatch[], int eflags) const
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{
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return regexec (&m_pattern, string, nmatch, pmatch, eflags);
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}
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int
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compiled_regex::search (const char *string,
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int length, int start, int range,
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struct re_registers *regs)
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{
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return re_search (&m_pattern, string, length, start, range, regs);
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}
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