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05f5f4f2746c2ee1346baaa58a0719e48fe84cc3
binutils-gdb/gdb/source-cache.c
Andrew Burgess 05f5f4f274 gdb: check styled status of source cache entries 
Currently GDB's source cache doesn't track whether the entries within
the cache are styled or not.  This is pretty much fine, the assumption
is that any time we are fetching source code, we do so in order to
print it to the terminal, so where possible we always want styling
applied, and if styling is not applied, then it is because that file
cannot be styled for some reason.

Changes to 'set style enabled' cause the source cache to be flushed,
so future calls to fetch source code will regenerate the cache entries
with styling enabled or not as appropriate.

But this all assumes that styling is either on or off, and that
switching between these two states isn't done very often.

However, the Python API allows for individual commands to be executed
with styling turned off via gdb.execute().  See commit:

  commit e5348a7ab3
  Date:   Thu Feb 13 15:39:31 2025 +0000

      gdb/python: new styling argument to gdb.execute

Currently the source cache doesn't handle this case. Consider this:

  (gdb) list main
  ... snip, styled source code displayed here ...
  (gdb) python gdb.execute("list main", True, False, False)
  ... snip, styled source code is still shown here ...

In the second case, the final `False` passed to gdb.execute() is
asking for unstyled output.

The problem is that, `get_source_lines` calls `ensure` to prime the
cache for the file in question, then `extract_lines` just pulls the
lines of interest from the cached contents.

In `ensure`, if there is a cache entry for the desired filename, then
that is considered good enough.  There is no consideration about
whether the cache entry is styled or not.

This commit aims to fix this, after this commit, the `ensure` function
will make sure that the cache entry used by `get_source_lines` is
styled correctly.

I think there are two approaches I could take:

  1. Allow multiple cache entries for a single file, a styled, and
     non-styled entry.  The `ensure` function would then place the
     correct cache entry into the last position so that
     `get_source_lines` would use the correct entry, or

  2. Have `ensure` recalculate entries if the required styling mode is
     different to the styling mode of the current entry.

Approach #1 is better if we are rapidly switching between styling
modes, while #2 might be better if we want to keep more files in the
cache and we only rarely switch styling modes.

In the end I chose approach #2, but the good thing is that the changes
are all contained within the `ensure` function.  If in the future we
wanted to change to strategy #1, this could be done transparently to
the rest of GDB.

So after this commit, the `ensure` function checks if styling is
currently possible or not.  If it is not, and the current entry is
styled, then the current entry only is dropped from the cache, and a
new, unstyled entry is created.  Likewise, if the current entry is
non-styled, but styling is required, we drop one entry and
recalculate.

With this change in place, I have updated set_style_enabled (in
cli/cli-style.c) so the source cache is no longer flushed when the
style settings are changed, the source cache will automatically handle
changes to the style settings now.

This problem was discovered in PR gdb/32676.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32676

Approved-By: Tom Tromey <tom@tromey.com>
2025-03-21 15:20:26 +00:00

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/* Cache of styled source file text
Copyright (C) 2018-2024 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 <http://www.gnu.org/licenses/>. */
#include "source-cache.h"
#include "gdbsupport/scoped_fd.h"
#include "source.h"
#include "cli/cli-style.h"
#include "symtab.h"
#include "objfiles.h"
#include "exec.h"
#include "cli/cli-cmds.h"
#ifdef HAVE_SOURCE_HIGHLIGHT
/* If Gnulib redirects 'open' and 'close' to its replacements
'rpl_open' and 'rpl_close' via cpp macros, including <fstream>
below with those macros in effect will cause unresolved externals
when GDB is linked. Happens, e.g., in the MinGW build. */
#undef open
#undef close
#include <sstream>
#include <srchilite/sourcehighlight.h>
#include <srchilite/langmap.h>
#include <srchilite/settings.h>
#endif
#if GDB_SELF_TEST
#include "gdbsupport/selftest.h"
#endif
/* The number of source files we'll cache. */
#define MAX_ENTRIES 5
/* See source-cache.h. */
source_cache g_source_cache;
/* When this is true we will use the GNU Source Highlight to add styling to
source code (assuming the library is available). This is initialized to
true (if appropriate) in _initialize_source_cache below. */
static bool use_gnu_source_highlight;
/* The "maint show gnu-source-highlight enabled" command. */
static void
show_use_gnu_source_highlight_enabled (struct ui_file *file, int from_tty,
struct cmd_list_element *c,
const char *value)
{
gdb_printf (file,
_("Use of GNU Source Highlight library is \"%s\".\n"),
value);
}
/* The "maint set gnu-source-highlight enabled" command. */
static void
set_use_gnu_source_highlight_enabled (const char *ignore_args,
int from_tty,
struct cmd_list_element *c)
{
#ifndef HAVE_SOURCE_HIGHLIGHT
/* If the library is not available and the user tried to enable use of
the library, then disable use of the library, and give an error. */
if (use_gnu_source_highlight)
{
use_gnu_source_highlight = false;
error (_("the GNU Source Highlight library is not available"));
}
#else
/* We (might) have just changed how we style source code, discard any
previously cached contents. */
forget_cached_source_info ();
#endif
}
/* See source-cache.h. */
std::string
source_cache::get_plain_source_lines (struct symtab *s,
const std::string &fullname)
{
scoped_fd desc (open_source_file (s));
if (desc.get () < 0)
perror_with_name (symtab_to_filename_for_display (s), -desc.get ());
struct stat st;
if (fstat (desc.get (), &st) < 0)
perror_with_name (symtab_to_filename_for_display (s));
std::string lines;
lines.resize (st.st_size);
if (myread (desc.get (), &lines[0], lines.size ()) < 0)
perror_with_name (symtab_to_filename_for_display (s));
time_t mtime = 0;
if (s->compunit ()->objfile () != NULL
&& s->compunit ()->objfile ()->obfd != NULL)
mtime = s->compunit ()->objfile ()->mtime;
else if (current_program_space->exec_bfd ())
mtime = current_program_space->ebfd_mtime;
if (mtime && mtime < st.st_mtime)
warning (_("Source file is more recent than executable."));
std::vector<off_t> offsets;
offsets.push_back (0);
for (size_t offset = lines.find ('\n');
offset != std::string::npos;
offset = lines.find ('\n', offset))
{
++offset;
/* A newline at the end does not start a new line. It would
seem simpler to just strip the newline in this function, but
then "list" won't print the final newline. */
if (offset != lines.size ())
offsets.push_back (offset);
}
offsets.shrink_to_fit ();
m_offset_cache.emplace (fullname, std::move (offsets));
return lines;
}
#ifdef HAVE_SOURCE_HIGHLIGHT
/* Return the Source Highlight language name, given a gdb language
LANG. Returns NULL if the language is not known. */
static const char *
get_language_name (enum language lang)
{
switch (lang)
{
case language_c:
case language_objc:
return "c.lang";
case language_cplus:
return "cpp.lang";
case language_d:
return "d.lang";
case language_go:
return "go.lang";
case language_fortran:
return "fortran.lang";
case language_m2:
/* Not handled by Source Highlight. */
break;
case language_asm:
return "asm.lang";
case language_pascal:
return "pascal.lang";
case language_opencl:
/* Not handled by Source Highlight. */
break;
case language_rust:
return "rust.lang";
case language_ada:
return "ada.lang";
default:
break;
}
return nullptr;
}
#endif /* HAVE_SOURCE_HIGHLIGHT */
/* Try to highlight CONTENTS from file FULLNAME in language LANG using
the GNU source-highlight library. Return true if highlighting
succeeded. */
static bool
try_source_highlight (std::string &contents ATTRIBUTE_UNUSED,
enum language lang ATTRIBUTE_UNUSED,
const std::string &fullname ATTRIBUTE_UNUSED)
{
#ifdef HAVE_SOURCE_HIGHLIGHT
if (!use_gnu_source_highlight)
return false;
const char *lang_name = get_language_name (lang);
/* The global source highlight object, or null if one was
never constructed. This is stored here rather than in
the class so that we don't need to include anything or do
conditional compilation in source-cache.h. */
static srchilite::SourceHighlight *highlighter;
/* The global source highlight language map object. */
static srchilite::LangMap *langmap;
bool styled = false;
try
{
if (highlighter == nullptr)
{
highlighter = new srchilite::SourceHighlight ("esc.outlang");
highlighter->setStyleFile ("esc.style");
const std::string &datadir = srchilite::Settings::retrieveDataDir ();
langmap = new srchilite::LangMap (datadir, "lang.map");
}
std::string detected_lang;
if (lang_name == nullptr)
{
detected_lang = langmap->getMappedFileNameFromFileName (fullname);
if (detected_lang.empty ())
return false;
lang_name = detected_lang.c_str ();
}
std::istringstream input (contents);
std::ostringstream output;
highlighter->highlight (input, output, lang_name, fullname);
contents = std::move (output).str ();
styled = true;
}
catch (...)
{
/* Source Highlight will throw an exception if
highlighting fails. One possible reason it can fail
is if the language is unknown -- which matters to gdb
because Rust support wasn't added until after 3.1.8.
Ignore exceptions here. */
}
return styled;
#else
return false;
#endif /* HAVE_SOURCE_HIGHLIGHT */
}
#ifdef HAVE_SOURCE_HIGHLIGHT
#if GDB_SELF_TEST
namespace selftests
{
static void gnu_source_highlight_test ()
{
const std::string prog
= ("int\n"
"foo (void)\n"
"{\n"
" return 0;\n"
"}\n");
const std::string fullname = "test.c";
std::string styled_prog;
bool res = false;
bool saw_exception = false;
styled_prog = prog;
try
{
res = try_source_highlight (styled_prog, language_c, fullname);
}
catch (const gdb_exception &e)
{
if (e.reason != RETURN_ERROR)
throw;
saw_exception = true;
}
catch (...)
{
saw_exception = true;
}
SELF_CHECK (!saw_exception);
if (res)
SELF_CHECK (prog.size () < styled_prog.size ());
else
SELF_CHECK (prog == styled_prog);
}
}
#endif /* GDB_SELF_TEST */
#endif /* HAVE_SOURCE_HIGHLIGHT */
/* See source-cache.h. */
bool
source_cache::ensure (struct symtab *s)
{
std::string fullname = symtab_to_fullname (s);
size_t size = m_source_map.size ();
for (int i = 0; i < size; ++i)
{
if (m_source_map[i].fullname == fullname)
{
/* This should always hold, because we create the file offsets
when reading the file. */
gdb_assert (m_offset_cache.find (fullname)
!= m_offset_cache.end ());
/* Not strictly LRU, but at least ensure that the most
recently used entry is always the last candidate for
deletion. Note that this property is relied upon by at
least one caller. */
if (i != size - 1)
std::swap (m_source_map[i], m_source_map[size - 1]);
/* If the styling status of the cached entry matches our desired
styling status, or we know this file cannot be styled, in
which case, this (unstyled) content, is the best we can do. */
if (((source_styling && gdb_stdout->can_emit_style_escape ())
== m_source_map[size - 1].styled)
|| m_no_styling_files.count (fullname) > 0)
return true;
/* We found a match, but styling status doesn't match the desired
styling status. We already moved the matching item to the
back of M_SOURCE_MAP, so drop the entry now, and then
recompute with the desired styling. */
m_source_map.pop_back ();
break;
}
}
std::string contents;
bool styled_p = false;
try
{
contents = get_plain_source_lines (s, fullname);
}
catch (const gdb_exception_error &e)
{
/* If 's' is not found, an exception is thrown. */
return false;
}
if (source_styling && gdb_stdout->can_emit_style_escape ()
&& m_no_styling_files.count (fullname) == 0)
{
styled_p
= try_source_highlight (contents, s->language (), fullname);
if (!styled_p)
{
std::optional<std::string> ext_contents;
ext_contents = ext_lang_colorize (fullname, contents);
if (ext_contents.has_value ())
{
contents = std::move (*ext_contents);
styled_p = true;
}
}
if (!styled_p)
{
/* Styling failed. Styling can fail for instance for these
reasons:
- the language is not supported.
- the language cannot not be auto-detected from the file name.
- no stylers available.
Since styling failed, don't try styling the file again after it
drops from the cache.
Note that clearing the source cache also clears
m_no_styling_files. */
m_no_styling_files.insert (fullname);
}
}
source_text result
= { std::move (fullname), std::move (contents), styled_p };
m_source_map.push_back (std::move (result));
if (m_source_map.size () > MAX_ENTRIES)
{
auto iter = m_source_map.begin ();
m_offset_cache.erase (iter->fullname);
m_source_map.erase (iter);
}
return true;
}
/* See source-cache.h. */
bool
source_cache::get_line_charpos (struct symtab *s,
const std::vector<off_t> **offsets)
{
std::string fullname = symtab_to_fullname (s);
auto iter = m_offset_cache.find (fullname);
if (iter == m_offset_cache.end ())
{
if (!ensure (s))
return false;
iter = m_offset_cache.find (fullname);
/* cache_source_text ensured this was entered. */
gdb_assert (iter != m_offset_cache.end ());
}
*offsets = &iter->second;
return true;
}
/* A helper function that extracts the desired source lines from TEXT,
putting them into LINES_OUT. The arguments are as for
get_source_lines. Returns true on success, false if the line
numbers are invalid. */
static bool
extract_lines (const std::string &text, int first_line, int last_line,
std::string *lines_out)
{
int lineno = 1;
std::string::size_type pos = 0;
std::string::size_type first_pos = std::string::npos;
while (pos != std::string::npos && lineno <= last_line)
{
std::string::size_type new_pos = text.find ('\n', pos);
if (lineno == first_line)
first_pos = pos;
pos = new_pos;
if (lineno == last_line || pos == std::string::npos)
{
/* A newline at the end does not start a new line. */
if (first_pos == std::string::npos
|| first_pos == text.size ())
return false;
if (pos == std::string::npos)
pos = text.size ();
else
++pos;
*lines_out = text.substr (first_pos, pos - first_pos);
return true;
}
++lineno;
++pos;
}
return false;
}
/* See source-cache.h. */
bool
source_cache::get_source_lines (struct symtab *s, int first_line,
int last_line, std::string *lines)
{
if (first_line < 1 || last_line < 1 || first_line > last_line)
return false;
if (!ensure (s))
return false;
return extract_lines (m_source_map.back ().contents,
first_line, last_line, lines);
}
/* Implement 'maint flush source-cache' command. */
static void
source_cache_flush_command (const char *command, int from_tty)
{
forget_cached_source_info ();
gdb_printf (_("Source cache flushed.\n"));
}
#if GDB_SELF_TEST
namespace selftests
{
static void extract_lines_test ()
{
std::string input_text = "abc\ndef\nghi\njkl\n";
std::string result;
SELF_CHECK (extract_lines (input_text, 1, 1, &result)
&& result == "abc\n");
SELF_CHECK (!extract_lines (input_text, 2, 1, &result));
SELF_CHECK (extract_lines (input_text, 1, 2, &result)
&& result == "abc\ndef\n");
SELF_CHECK (extract_lines ("abc", 1, 1, &result)
&& result == "abc");
}
}
#endif
void _initialize_source_cache ();
void
_initialize_source_cache ()
{
add_cmd ("source-cache", class_maintenance, source_cache_flush_command,
_("Force gdb to flush its source code cache."),
&maintenanceflushlist);
/* All the 'maint set|show gnu-source-highlight' sub-commands. */
static struct cmd_list_element *maint_set_gnu_source_highlight_cmdlist;
static struct cmd_list_element *maint_show_gnu_source_highlight_cmdlist;
/* Adds 'maint set|show gnu-source-highlight'. */
add_setshow_prefix_cmd ("gnu-source-highlight", class_maintenance,
_("Set gnu-source-highlight specific variables."),
_("Show gnu-source-highlight specific variables."),
&maint_set_gnu_source_highlight_cmdlist,
&maint_show_gnu_source_highlight_cmdlist,
&maintenance_set_cmdlist,
&maintenance_show_cmdlist);
/* Adds 'maint set|show gnu-source-highlight enabled'. */
add_setshow_boolean_cmd ("enabled", class_maintenance,
&use_gnu_source_highlight, _("\
Set whether the GNU Source Highlight library should be used."), _("\
Show whether the GNU Source Highlight library is being used."),_("\
When enabled, GDB will use the GNU Source Highlight library to apply\n\
styling to source code lines that are shown."),
set_use_gnu_source_highlight_enabled,
show_use_gnu_source_highlight_enabled,
&maint_set_gnu_source_highlight_cmdlist,
&maint_show_gnu_source_highlight_cmdlist);
/* Enable use of GNU Source Highlight library, if we have it. */
#ifdef HAVE_SOURCE_HIGHLIGHT
use_gnu_source_highlight = true;
#endif
#if GDB_SELF_TEST
selftests::register_test ("source-cache", selftests::extract_lines_test);
#ifdef HAVE_SOURCE_HIGHLIGHT
selftests::register_test ("gnu-source-highlight",
selftests::gnu_source_highlight_test);
#endif
#endif
}
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