Fix latent bug in source cache

[deliverable/binutils-gdb.git] / gdb / source-cache.c

/* Cache of styled source file text
   Copyright (C) 2018-2019 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 "defs.h"
#include "source-cache.h"
#include "gdbsupport/scoped_fd.h"
#include "source.h"
#include "cli/cli-style.h"
#include "symtab.h"
#include "gdbsupport/selftest.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 <fstream>
#include <sstream>
#include <srchilite/sourcehighlight.h>
#include <srchilite/langmap.h>
#endif

/* The number of source files we'll cache.  */

#define MAX_ENTRIES 5

/* See source-cache.h.  */

source_cache g_source_cache;

/* See source-cache.h.  */

bool
source_cache::get_plain_source_lines (struct symtab *s, int first_line,
				      int last_line, std::string *lines)
{
  scoped_fd desc (open_source_file_with_line_charpos (s));
  if (desc.get () < 0)
    return false;

  if (first_line < 1 || first_line > s->nlines || last_line < 1)
    return false;

  if (lseek (desc.get (), s->line_charpos[first_line - 1], SEEK_SET) < 0)
    perror_with_name (symtab_to_filename_for_display (s));

  int last_charpos;
  if (last_line >= s->nlines)
    {
      struct stat st;

      if (fstat (desc.get (), &st) < 0)
	perror_with_name (symtab_to_filename_for_display (s));
      /* We could cache this in line_charpos... */
      last_charpos = st.st_size;
    }
  else
    last_charpos = s->line_charpos[last_line];

  lines->resize (last_charpos - s->line_charpos[first_line - 1]);
  if (myread (desc.get (), &(*lines)[0], lines->size ()) < 0)
    perror_with_name (symtab_to_filename_for_display (s));

  return true;
}

/* A helper function for get_plain_source_lines that extracts the
   desired source lines from TEXT, putting them into LINES_OUT.  The
   arguments are as for get_source_lines.  The return value is the
   desired lines.  */
static std::string
extract_lines (const std::string &text, int first_line, int last_line)
{
  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)
	{
	  if (first_pos == std::string::npos)
	    return {};
	  if (pos == std::string::npos)
	    pos = text.size ();
	  else
	    ++pos;
	  return text.substr (first_pos, pos - first_pos);
	}
      ++lineno;
      ++pos;
    }

  return {};
}

#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:
      /* Not handled by Source Highlight.  */
      break;

    case language_ada:
      return "ada.lang";

    default:
      break;
    }

  return nullptr;
}

#endif /* HAVE_SOURCE_HIGHLIGHT */

/* 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;

#ifdef HAVE_SOURCE_HIGHLIGHT
  if (source_styling && gdb_stdout->can_emit_style_escape ())
    {
      const char *fullname = symtab_to_fullname (s);

      for (const auto &item : m_source_map)
	{
	  if (item.fullname == fullname)
	    {
	      *lines = extract_lines (item.contents, first_line, last_line);
	      return true;
	    }
	}

      const char *lang_name = get_language_name (SYMTAB_LANGUAGE (s));
      if (lang_name != nullptr)
	{
	  std::ifstream input (fullname);
	  if (input.is_open ())
	    {
	      /* 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;

	      if (s->line_charpos == 0)
		{
		  scoped_fd desc (open_source_file_with_line_charpos (s));
		  if (desc.get () < 0)
		    return false;

		  /* FULLNAME points to a value owned by the symtab
		     (symtab::fullname).  Calling open_source_file reallocates
		     that value, so we must refresh FULLNAME to avoid a
		     use-after-free.  */
		  fullname = symtab_to_fullname (s);
		}

	      if (highlighter == nullptr)
		{
		  highlighter = new srchilite::SourceHighlight ("esc.outlang");
		  highlighter->setStyleFile ("esc.style");
		}

	      std::ostringstream output;
	      highlighter->highlight (input, output, lang_name, fullname);

	      source_text result = { fullname, output.str () };
	      m_source_map.push_back (std::move (result));

	      if (m_source_map.size () > MAX_ENTRIES)
		m_source_map.erase (m_source_map.begin ());

	      *lines = extract_lines (m_source_map.back ().contents,
				      first_line, last_line);
	      return true;
	    }
	}
    }
#endif /* HAVE_SOURCE_HIGHLIGHT */

  return get_plain_source_lines (s, first_line, last_line, lines);
}

#if GDB_SELF_TEST
namespace selftests
{
static void extract_lines_test ()
{
  std::string input_text = "abc\ndef\nghi\njkl\n";

  SELF_CHECK (extract_lines (input_text, 1, 1) == "abc\n");
  SELF_CHECK (extract_lines (input_text, 2, 1) == "");
  SELF_CHECK (extract_lines (input_text, 1, 2) == "abc\ndef\n");
  SELF_CHECK (extract_lines ("abc", 1, 1) == "abc");
}
}
#endif

void
_initialize_source_cache ()
{
#if GDB_SELF_TEST
  selftests::register_test ("source-cache", selftests::extract_lines_test);
#endif
}