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e0700ba44c
String-like settings (var_string, var_filename, var_optional_filename, var_string_noescape) currently take a pointer to a `char *` storage variable (typically global) that holds the setting's value. I'd like to "mordernize" this by changing them to use an std::string for storage. An obvious reason is that string operations on std::string are often easier to write than with C strings. And they avoid having to do any manual memory management. Another interesting reason is that, with `char *`, nullptr and an empty string often both have the same meaning of "no value". String settings are initially nullptr (unless initialized otherwise). But when doing "set foo" (where `foo` is a string setting), the setting now points to an empty string. For example, solib_search_path is nullptr at startup, but points to an empty string after doing "set solib-search-path". This leads to some code that needs to check for both to check for "no value". Or some code that converts back and forth between NULL and "" when getting or setting the value. I find this very error-prone, because it is very easy to forget one or the other. With std::string, we at least know that the variable is not "NULL". There is only one way of representing an empty string setting, that is with an empty string. I was wondering whether the distinction between NULL and "" would be important for some setting, but it doesn't seem so. If that ever happens, it would be more C++-y and self-descriptive to use optional<string> anyway. Actually, there's one spot where this distinction mattered, it's in init_history, for the test gdb.base/gdbinit-history.exp. init_history sets the history filename to the default ".gdb_history" if it sees that the setting was never set - if history_filename is nullptr. If history_filename is an empty string, it means the setting was explicitly cleared, so it leaves it as-is. With the change to std::string, this distinction doesn't exist anymore. This can be fixed by moving the code that chooses a good default value for history_filename to _initialize_top. This is ran before -ex commands are processed, so an -ex command can then clear that value if needed (what gdb.base/gdbinit-history.exp tests). Another small improvement, in my opinion is that we can now easily give string parameters initial values, by simply initializing the global variables, instead of xstrdup-ing it in the _initialize function. In Python and Guile, when registering a string-like parameter, we allocate (with new) an std::string that is owned by the param_smob (in Guile) and the parmpy_object (in Python) objects. This patch started by changing all relevant add_setshow_* commands to take an `std::string *` instead of a `char **` and fixing everything that failed to build. That includes of course all string setting variable and their uses. string_option_def now uses an std::string also, because there's a connection between options and settings (see add_setshow_cmds_for_options). The add_path function in source.c is really complex and twisted, I'd rather not try to change it to work on an std::string right now. Instead, I added an overload that copies the std:string to a `char *` and back. This means more copying, but this is not used in a hot path at all, so I think it is acceptable. Change-Id: I92c50a1bdd8307141cdbacb388248e4e4fc08c93 Co-authored-by: Lancelot SIX <lsix@lancelotsix.com>
377 lines
10 KiB
C
377 lines
10 KiB
C
/* Caching of GDB/DWARF index files.
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Copyright (C) 1994-2021 Free Software Foundation, Inc.
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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 "dwarf2/index-cache.h"
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#include "build-id.h"
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#include "cli/cli-cmds.h"
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#include "command.h"
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#include "gdbsupport/scoped_mmap.h"
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#include "gdbsupport/pathstuff.h"
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#include "dwarf2/index-write.h"
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#include "dwarf2/read.h"
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#include "dwarf2/dwz.h"
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#include "objfiles.h"
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#include "gdbsupport/selftest.h"
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#include <string>
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#include <stdlib.h>
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/* When set to true, show debug messages about the index cache. */
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static bool debug_index_cache = false;
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/* The index cache directory, used for "set/show index-cache directory". */
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static std::string index_cache_directory;
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/* See dwarf-index.cache.h. */
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index_cache global_index_cache;
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/* set/show index-cache commands. */
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static cmd_list_element *set_index_cache_prefix_list;
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static cmd_list_element *show_index_cache_prefix_list;
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/* Default destructor of index_cache_resource. */
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index_cache_resource::~index_cache_resource () = default;
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/* See dwarf-index-cache.h. */
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void
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index_cache::set_directory (std::string dir)
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{
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gdb_assert (!dir.empty ());
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m_dir = std::move (dir);
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if (debug_index_cache)
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printf_unfiltered ("index cache: now using directory %s\n", m_dir.c_str ());
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}
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/* See dwarf-index-cache.h. */
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void
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index_cache::enable ()
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{
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if (debug_index_cache)
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printf_unfiltered ("index cache: enabling (%s)\n", m_dir.c_str ());
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m_enabled = true;
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}
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/* See dwarf-index-cache.h. */
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void
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index_cache::disable ()
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{
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if (debug_index_cache)
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printf_unfiltered ("index cache: disabling\n");
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m_enabled = false;
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}
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/* See dwarf-index-cache.h. */
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void
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index_cache::store (dwarf2_per_objfile *per_objfile)
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{
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objfile *obj = per_objfile->objfile;
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if (!enabled ())
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return;
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/* Get build id of objfile. */
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const bfd_build_id *build_id = build_id_bfd_get (obj->obfd);
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if (build_id == nullptr)
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{
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if (debug_index_cache)
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printf_unfiltered ("index cache: objfile %s has no build id\n",
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objfile_name (obj));
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return;
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}
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std::string build_id_str = build_id_to_string (build_id);
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/* Get build id of dwz file, if present. */
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gdb::optional<std::string> dwz_build_id_str;
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const dwz_file *dwz = dwarf2_get_dwz_file (per_objfile->per_bfd);
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const char *dwz_build_id_ptr = NULL;
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if (dwz != nullptr)
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{
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const bfd_build_id *dwz_build_id = build_id_bfd_get (dwz->dwz_bfd.get ());
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if (dwz_build_id == nullptr)
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{
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if (debug_index_cache)
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printf_unfiltered ("index cache: dwz objfile %s has no build id\n",
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dwz->filename ());
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return;
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}
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dwz_build_id_str = build_id_to_string (dwz_build_id);
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dwz_build_id_ptr = dwz_build_id_str->c_str ();
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}
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if (m_dir.empty ())
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{
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warning (_("The index cache directory name is empty, skipping store."));
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return;
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}
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try
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{
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/* Try to create the containing directory. */
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if (!mkdir_recursive (m_dir.c_str ()))
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{
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warning (_("index cache: could not make cache directory: %s"),
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safe_strerror (errno));
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return;
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}
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if (debug_index_cache)
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printf_unfiltered ("index cache: writing index cache for objfile %s\n",
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objfile_name (obj));
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/* Write the index itself to the directory, using the build id as the
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filename. */
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write_psymtabs_to_index (per_objfile, m_dir.c_str (),
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build_id_str.c_str (), dwz_build_id_ptr,
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dw_index_kind::GDB_INDEX);
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}
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catch (const gdb_exception_error &except)
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{
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if (debug_index_cache)
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printf_unfiltered ("index cache: couldn't store index cache for objfile "
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"%s: %s", objfile_name (obj), except.what ());
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}
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}
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#if HAVE_SYS_MMAN_H
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/* Hold the resources for an mmapped index file. */
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struct index_cache_resource_mmap final : public index_cache_resource
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{
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/* Try to mmap FILENAME. Throw an exception on failure, including if the
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file doesn't exist. */
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index_cache_resource_mmap (const char *filename)
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: mapping (mmap_file (filename))
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{}
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scoped_mmap mapping;
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};
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/* See dwarf-index-cache.h. */
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gdb::array_view<const gdb_byte>
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index_cache::lookup_gdb_index (const bfd_build_id *build_id,
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std::unique_ptr<index_cache_resource> *resource)
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{
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if (!enabled ())
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return {};
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if (m_dir.empty ())
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{
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warning (_("The index cache directory name is empty, skipping cache "
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"lookup."));
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return {};
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}
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/* Compute where we would expect a gdb index file for this build id to be. */
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std::string filename = make_index_filename (build_id, INDEX4_SUFFIX);
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try
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{
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if (debug_index_cache)
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printf_unfiltered ("index cache: trying to read %s\n",
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filename.c_str ());
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/* Try to map that file. */
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index_cache_resource_mmap *mmap_resource
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= new index_cache_resource_mmap (filename.c_str ());
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/* Yay, it worked! Hand the resource to the caller. */
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resource->reset (mmap_resource);
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return gdb::array_view<const gdb_byte>
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((const gdb_byte *) mmap_resource->mapping.get (),
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mmap_resource->mapping.size ());
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}
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catch (const gdb_exception_error &except)
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{
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if (debug_index_cache)
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printf_unfiltered ("index cache: couldn't read %s: %s\n",
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filename.c_str (), except.what ());
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}
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return {};
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}
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#else /* !HAVE_SYS_MMAN_H */
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/* See dwarf-index-cache.h. This is a no-op on unsupported systems. */
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gdb::array_view<const gdb_byte>
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index_cache::lookup_gdb_index (const bfd_build_id *build_id,
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std::unique_ptr<index_cache_resource> *resource)
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{
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return {};
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}
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#endif
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/* See dwarf-index-cache.h. */
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std::string
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index_cache::make_index_filename (const bfd_build_id *build_id,
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const char *suffix) const
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{
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std::string build_id_str = build_id_to_string (build_id);
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return m_dir + SLASH_STRING + build_id_str + suffix;
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}
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/* True when we are executing "show index-cache". This is used to improve the
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printout a little bit. */
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static bool in_show_index_cache_command = false;
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/* "show index-cache" handler. */
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static void
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show_index_cache_command (const char *arg, int from_tty)
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{
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/* Note that we are executing "show index-cache". */
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auto restore_flag = make_scoped_restore (&in_show_index_cache_command, true);
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/* Call all "show index-cache" subcommands. */
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cmd_show_list (show_index_cache_prefix_list, from_tty);
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printf_unfiltered ("\n");
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printf_unfiltered
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(_("The index cache is currently %s.\n"),
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global_index_cache.enabled () ? _("enabled") : _("disabled"));
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}
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/* "set index-cache on" handler. */
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static void
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set_index_cache_on_command (const char *arg, int from_tty)
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{
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global_index_cache.enable ();
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}
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/* "set index-cache off" handler. */
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static void
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set_index_cache_off_command (const char *arg, int from_tty)
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{
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global_index_cache.disable ();
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}
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/* "set index-cache directory" handler. */
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static void
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set_index_cache_directory_command (const char *arg, int from_tty,
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cmd_list_element *element)
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{
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/* Make sure the index cache directory is absolute and tilde-expanded. */
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gdb::unique_xmalloc_ptr<char> abs
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= gdb_abspath (index_cache_directory.c_str ());
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index_cache_directory = abs.get ();
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global_index_cache.set_directory (index_cache_directory);
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}
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/* "show index-cache stats" handler. */
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static void
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show_index_cache_stats_command (const char *arg, int from_tty)
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{
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const char *indent = "";
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/* If this command is invoked through "show index-cache", make the display a
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bit nicer. */
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if (in_show_index_cache_command)
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{
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indent = " ";
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printf_unfiltered ("\n");
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}
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printf_unfiltered (_("%s Cache hits (this session): %u\n"),
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indent, global_index_cache.n_hits ());
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printf_unfiltered (_("%sCache misses (this session): %u\n"),
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indent, global_index_cache.n_misses ());
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}
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void _initialize_index_cache ();
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void
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_initialize_index_cache ()
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{
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/* Set the default index cache directory. */
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std::string cache_dir = get_standard_cache_dir ();
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if (!cache_dir.empty ())
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{
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index_cache_directory = cache_dir;
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global_index_cache.set_directory (std::move (cache_dir));
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}
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else
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warning (_("Couldn't determine a path for the index cache directory."));
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/* set index-cache */
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add_basic_prefix_cmd ("index-cache", class_files,
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_("Set index-cache options."),
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&set_index_cache_prefix_list,
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false, &setlist);
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/* show index-cache */
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add_prefix_cmd ("index-cache", class_files, show_index_cache_command,
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_("Show index-cache options."), &show_index_cache_prefix_list,
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false, &showlist);
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/* set index-cache on */
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add_cmd ("on", class_files, set_index_cache_on_command,
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_("Enable the index cache."), &set_index_cache_prefix_list);
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/* set index-cache off */
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add_cmd ("off", class_files, set_index_cache_off_command,
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_("Disable the index cache."), &set_index_cache_prefix_list);
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/* set index-cache directory */
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add_setshow_filename_cmd ("directory", class_files, &index_cache_directory,
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_("Set the directory of the index cache."),
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_("Show the directory of the index cache."),
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NULL,
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set_index_cache_directory_command, NULL,
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&set_index_cache_prefix_list,
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&show_index_cache_prefix_list);
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/* show index-cache stats */
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add_cmd ("stats", class_files, show_index_cache_stats_command,
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_("Show some stats about the index cache."),
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&show_index_cache_prefix_list);
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/* set debug index-cache */
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add_setshow_boolean_cmd ("index-cache", class_maintenance,
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&debug_index_cache,
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_("Set display of index-cache debug messages."),
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_("Show display of index-cache debug messages."),
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_("\
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When non-zero, debugging output for the index cache is displayed."),
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NULL, NULL,
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&setdebuglist, &showdebuglist);
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}
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