Re: [PATCH] preprocessor/58580 - preprocessor goes OOM with warning for zero literals

[Dodji Seketeli <dodji at redhat dot com>]

Hello,

As it appeared that concerns about the speed of
location_get_source_line were as present as the need of just fixing
this bug, I have conflated the two concerns in a new attempt below,
trying to address the points you guys have raised during the previous
reviews.

The patch below introduces a cache for the data read from the file we
want to emit caret diagnostic for.  In that cache it stashes the bytes
read from the file as well as a number of positions of line delimiters
that we encountered while reading the file.  It keeps a number of the
last file caches in memory in case location_get_source_line is later
asked for lines from the same file.

To avoid exploding the memory consumption, the number line delimiter
position saved is fixed (100).  So if a file is smaller than 100 lines
all of its line positions can be saved.  That is, if
location_get_source_line is first asked to return line 20, all the
position of the lines encountered since the beginning of the file --
up to line 20 -- are going to be saved in the cache.  Next time, if
location_get_source_line is asked to return line 10, as the position
of the beginning/end of line 10 is saved in the cache, returning that
line is fast.  If it's asked to return line 25, it will have to start
reading from line 20, not from the beginning of the file.

If the file is bigger than 100, then the patch just saves 100 line
positions.  To evenly spread the line position saved, it needs to know
the total number lines of the file.  Luckily we can usually get this
information from the line map subsystem (from libcpp).  The patch thus
adds a new entry point in the line map
(linemap_get_file_highest_location) that gives the greatest
source_location seen for a given file and uses that to decide what
line position to save in the cache.

The speed gain I have seen is variable, depending on the size (in
number of quasi adjacent lines) of the diagnostics, but on some
pathological cases I have seen, it can divide the time spend
displaying the diagnostics by two ore more.  I had to add hackery in
the code to measure this, unfortunately :-(

The patch doesn't try to reuse the same infrastructure for gcov for
now.  I am letting that for later now when I have more time.

Bootstrapped on x86_64-unknown-linux-gnu against trunk.

PS: To ease the review (especially for Tom Tromey who I am CC-ing
because of the new entry point in the line map sub-system) I am
attaching the cover letter of the patch itself that does the analysis
of the initial bug.  Sorry to the other addressees of this message for
the redundancy.

Thanks.


---------------------------------------->8<-------------------------------
In this problem report, the compiler is fed a (bogus) translation unit
in which some literals contain bytes whose value is zero.  The
preprocessor detects that and proceeds to emit diagnostics for that
king of bogus literals.  But then when the diagnostics machinery
re-reads the input file again to display the bogus literals with a
caret, it attempts to calculate the length of each of the lines it got
using fgets.  The line length calculation is done using strlen.  But
that doesn't work well when the content of the line can have several
zero bytes.  The result is that the read_line never sees the end of
the line because strlen repeatedly reports that the line ends before
the end-of-line character; so read_line thinks its buffer for reading
the line is too small; it thus increases the buffer, leading to a huge
memory consumption and disaster.

Here is what this patch does.

location_get_source_line is modified to return the length of a source
line that can now contain bytes with zero value.
diagnostic_show_locus() is then modified to consider that a line can
have characters of value zero, and so just shows a white space when
instructed to display one of these characters.

Additionally location_get_source_line is modified to avoid re-reading
each and every line from the beginning of the file until it reaches
the line number N that it is instructed to get; this was leading to
annoying quadratic behaviour when reading adjacent lines near the end
of (big) files.  So a cache is now associated to the file opened in
text mode.  When the content of the file is read, that content is
stashed in the file cache.  That file cache is searched for line
delimiters.  A number of line positions are saved in the cache and a
number of file caches are kept in memory.  That way when
location_get_source_line is asked to read line N + 1, it just has to
start reading from line N that it has already read.
---------------------------------------->8<-------------------------------

And now the real patch.

libcpp/ChangeLog:

	* include/line-map.h (linemap_get_file_highest_location): Declare
	new function.
	* line-map.c (linemap_get_file_highest_location): Define it.

gcc/ChangeLog:

	* input.h (location_get_source_line): Take an additional line_size
	parameter.
	(void diagnostics_file_cache_fini): Declare new function.
	* input.c (struct fcache): New type.
	(fcache_tab_size, fcache_buffer_size, fcache_line_record_size):
	New static constants.
	(diagnostic_file_cache_init, lookup_file_in_cache_tab)
	(add_file_to_cache_tab, lookup_or_add_file_to_cache_tab)
	(needs_read, needs_grow, maybe_grow, read_data, maybe_read_data)
	(get_next_line, read_next_line, goto_next_line, read_line_num):
	New static function definitions.
	(diagnostic_file_cache_fini): New function.
	(location_get_source_line): Take an additional output line_len
	parameter.  Re-write using lookup_or_add_file_to_cache_tab and
	read_line_num.
	* diagnostic.c (diagnostic_finish): Call
	diagnostic_file_cache_fini.
	(adjust_line): Take an additional input parameter for the length
	of the line, rather than calculating it with strlen.
	(diagnostic_show_locus): Adjust the use of
	location_get_source_line and adjust_line with respect to their new
	signature.  While displaying a line now, do not stop at the first
	null byte.  Rather, display the zero byte as a space and keep
	going until we reach the size of the line.
	* Makefile.in: Add vec.o to OBJS-libcommon

gcc/testsuite/ChangeLog:

	* c-c++-common/cpp/warning-zero-in-literals-1.c: New test file.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@204453 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/Makefile.in                                    |   2 +-
 gcc/diagnostic.c                                   |  19 +-
 gcc/diagnostic.h                                   |   1 +
 gcc/input.c                                        | 549 +++++++++++++++++++--
 gcc/input.h                                        |   5 +-
 .../c-c++-common/cpp/warning-zero-in-literals-1.c  | Bin 0 -> 240 bytes
 libcpp/include/line-map.h                          |   8 +
 libcpp/line-map.c                                  |  40 ++
 8 files changed, 585 insertions(+), 39 deletions(-)
 create mode 100644 gcc/testsuite/c-c++-common/cpp/warning-zero-in-literals-1.c

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 49285e5..50c2482 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1469,7 +1469,7 @@ OBJS = \
 
 # Objects in libcommon.a, potentially used by all host binaries and with
 # no target dependencies.
-OBJS-libcommon = diagnostic.o diagnostic-color.o pretty-print.o intl.o input.o version.o
+OBJS-libcommon = diagnostic.o diagnostic-color.o pretty-print.o intl.o vec.o input.o version.o
 
 # Objects in libcommon-target.a, used by drivers and by the core
 # compiler and containing target-dependent code.
diff --git a/gcc/diagnostic.c b/gcc/diagnostic.c
index 36094a1..6c83f03 100644
--- a/gcc/diagnostic.c
+++ b/gcc/diagnostic.c
@@ -176,6 +176,8 @@ diagnostic_finish (diagnostic_context *context)
 		     progname);
       pp_newline_and_flush (context->printer);
     }
+
+  diagnostic_file_cache_fini ();
 }
 
 /* Initialize DIAGNOSTIC, where the message MSG has already been
@@ -259,12 +261,13 @@ diagnostic_build_prefix (diagnostic_context *context,
    MAX_WIDTH by some margin, then adjust the start of the line such
    that the COLUMN is smaller than MAX_WIDTH minus the margin.  The
    margin is either 10 characters or the difference between the column
-   and the length of the line, whatever is smaller.  */
+   and the length of the line, whatever is smaller.  The length of
+   LINE is given by LINE_WIDTH.  */
 static const char *
-adjust_line (const char *line, int max_width, int *column_p)
+adjust_line (const char *line, int line_width,
+	     int max_width, int *column_p)
 {
   int right_margin = 10;
-  int line_width = strlen (line);
   int column = *column_p;
 
   right_margin = MIN (line_width - column, right_margin);
@@ -284,6 +287,7 @@ diagnostic_show_locus (diagnostic_context * context,
 		       const diagnostic_info *diagnostic)
 {
   const char *line;
+  int line_width;
   char *buffer;
   expanded_location s;
   int max_width;
@@ -297,22 +301,25 @@ diagnostic_show_locus (diagnostic_context * context,
 
   context->last_location = diagnostic->location;
   s = expand_location_to_spelling_point (diagnostic->location);
-  line = location_get_source_line (s);
+  line = location_get_source_line (s, &line_width);
   if (line == NULL)
     return;
 
   max_width = context->caret_max_width;
-  line = adjust_line (line, max_width, &(s.column));
+  line = adjust_line (line, line_width, max_width, &(s.column));
 
   pp_newline (context->printer);
   saved_prefix = pp_get_prefix (context->printer);
   pp_set_prefix (context->printer, NULL);
   pp_space (context->printer);
-  while (max_width > 0 && *line != '\0')
+  while (max_width > 0 && line_width > 0)
     {
       char c = *line == '\t' ? ' ' : *line;
+      if (c == '\0')
+	c = ' ';
       pp_character (context->printer, c);
       max_width--;
+      line_width--;
       line++;
     }
   pp_newline (context->printer);
diff --git a/gcc/diagnostic.h b/gcc/diagnostic.h
index cb38d37..3f30e06 100644
--- a/gcc/diagnostic.h
+++ b/gcc/diagnostic.h
@@ -291,6 +291,7 @@ void default_diagnostic_starter (diagnostic_context *, diagnostic_info *);
 void default_diagnostic_finalizer (diagnostic_context *, diagnostic_info *);
 void diagnostic_set_caret_max_width (diagnostic_context *context, int value);
 
+void diagnostic_file_cache_fini (void);
 
 /* Pure text formatting support functions.  */
 extern char *file_name_as_prefix (diagnostic_context *, const char *);
diff --git a/gcc/input.c b/gcc/input.c
index a141a92..06a0f35 100644
--- a/gcc/input.c
+++ b/gcc/input.c
@@ -22,6 +22,75 @@ along with GCC; see the file COPYING3.  If not see
 #include "coretypes.h"
 #include "intl.h"
 #include "input.h"
+#include "vec.h"
+
+/* This is a cache used by get_next_line to store the content of a
+   file to be searched for file lines.  */
+struct fcache
+{
+  /* These are information used to store a line boundary.  */
+  struct line_info
+  {
+    /* The line number.  It starts from 1.  */
+    size_t line_num;
+
+    /* The position (byte count) of the beginning of the line,
+       relative to the file data pointer.  This starts at zero.  */
+    size_t start_pos;
+
+    /* The position (byte count) the the last byte of the line.  This
+       normally points to the '\n' character, or to one byte after the
+       last byte of the file, if the file doesn't contain a '\n'
+       character.  */
+    size_t end_pos;
+
+    line_info (size_t l, size_t s, size_t e)
+      : line_num (l), start_pos (s), end_pos (e)
+    {}
+
+    line_info ()
+      :line_num (0), start_pos (0), end_pos (0)
+    {}
+  };
+
+  const char *file_path;
+
+  FILE *fp;
+
+  /* This points to the content of the file that we've read so
+     far.  */
+  char *data;
+
+  /*  The size of the DATA array above.*/
+  size_t size;
+
+  /* The number of bytes read from the underlying file so far.  This
+     must be less (or equal) than SIZE above.  */
+  size_t nb_read;
+
+  /* The index of the beginning of the current line.  */
+  size_t line_start_idx;
+
+  /* The number of the previous line read.  This starts at 1.  Zero
+     means we've read no line so far.  */
+  size_t line_num;
+
+  /* This is the total number of lines of the current file.  At the
+     moment, we try to get this information from the line map.  */
+  size_t total_lines;
+
+  /* This is a record of the beginning and end of the lines we've seen
+     while reading the file.  This is useful to avoid walking the data
+     from the beginning when we are asked to read a line that is
+     before LINE_START_IDX above.  Note that the maximum size of this
+     record is fcache_line_record_size, so that the memory consumption
+     doesn't explode.  We thus scale total_lines down to
+     fcache_line_record_size.  */
+  vec<line_info, va_heap> line_record;
+
+  fcache ();
+  ~fcache ();
+};
 
 /* Current position in real source file.  */
 
@@ -29,6 +98,11 @@ location_t input_location;
 
 struct line_maps *line_table;
 
+static fcache *fcache_tab;
+static const size_t fcache_tab_size = 16;
+static const size_t fcache_buffer_size = 4 * 1024;
+static const size_t fcache_line_record_size = 100;
+
 /* Expand the source location LOC into a human readable location.  If
    LOC resolves to a builtin location, the file name of the readable
    location is set to the string "<built-in>". If EXPANSION_POINT_P is
@@ -87,56 +161,469 @@ expand_location_1 (source_location loc,
   return xloc;
 }
 
-/* Reads one line from file into a static buffer.  */
-static const char *
-read_line (FILE *file)
+/* Initialize the set of cache used for files accessed by caret
+   diagnostic.  */
+
+static void
+diagnostic_file_cache_init (void)
+{
+  if (fcache_tab == NULL)
+    fcache_tab = new fcache[fcache_tab_size];
+}
+
+/* Free the ressources used by the set of cache used for files accessed
+   by caret diagnostic.  */
+
+void
+diagnostic_file_cache_fini (void)
+{
+  if (fcache_tab)
+    {
+      delete [] (fcache_tab);
+      fcache_tab = NULL;
+    }
+}
+
+/* Lookup the cache used for the content of a given file accessed by
+   caret diagnostic.  Return the found cached file, or NULL if no
+   cached file was found.  */
+
+static fcache*
+lookup_file_in_cache_tab (const char *file_path)
+{
+  diagnostic_file_cache_init ();
+
+  for (unsigned i = 0; i < fcache_tab_size; ++i)
+    if (fcache_tab[i].file_path && !strcmp (fcache_tab[i].file_path, file_path))
+      return &fcache_tab[i];
+
+  return NULL;
+}
+
+/* Create the cache used for the content of a given file to be
+   accessed by caret diagnostic.  This cache is added to an array of
+   cache and can be retrieved by lookup_file_in_cache_tab.  This
+   function returns the created cache.  Note that only the last
+   fcache_tab_size files are cached.  */
+
+static fcache*
+add_file_to_cache_tab (const char *file_path)
+{
+  static size_t idx;
+  fcache *r;
+
+  FILE *fp = fopen (file_path, "r");
+  if (ferror (fp))
+    {
+      fclose (fp);
+      return NULL;
+    }
+
+  r = &fcache_tab[idx];
+  r->file_path = file_path;
+  if (r->fp)
+    fclose (r->fp);
+  r->fp = fp;
+  r->nb_read = 0;
+  r->line_start_idx = 0;
+  r->line_num = 0;
+  r->line_record.truncate (0);
+
+  source_location l = 0;
+  if (linemap_get_file_highest_location (line_table, file_path, &l))
+    {
+      gcc_assert (l >= RESERVED_LOCATION_COUNT);
+      expanded_location xloc = expand_location (l);
+      r->total_lines = xloc.line;
+    }
+
+  /* Increment idx, modulo fcache_tab_size.  */
+  ++idx;
+  idx = idx % fcache_tab_size;
+
+  return r;
+}
+
+/* Lookup the cache used for the content of a given file accessed by
+   caret diagnostic.  If no cached file was found, create a new cache
+   for this file, add it to the array of cached file and return
+   it.  */
+
+static fcache*
+lookup_or_add_file_to_cache_tab (const char *file_path)
+{
+  fcache * r = lookup_file_in_cache_tab (file_path);
+  if (r ==  NULL)
+    r = add_file_to_cache_tab (file_path);
+  return r;
+}
+
+/* Default constructor for a cache of file used by caret
+   diagnostic.  */
+
+fcache::fcache ()
+: file_path (NULL), fp (NULL), data (0),
+  size (0), nb_read (0), line_start_idx (0), line_num (0),
+  total_lines (0)
+{
+  line_record.create (0);
+}
+
+/* Destructor for a cache of file used by caret diagnostic.  */
+
+fcache::~fcache ()
+{
+  if (fp)
+    {
+      fclose (fp);
+      fp = NULL;
+    }
+  if (data)
+    {
+      XDELETEVEC (data);
+      data = 0;
+    }
+  line_record.release ();
+}
+
+/* Returns TRUE iff the cache would need to be filled with data coming
+   from the file.  That is, either the cache is empty or full or the
+   current line is empty.  Note that if the cache is full, it would
+   need to be extended and filled again.  */
+
+static bool
+needs_read (fcache *c)
+{
+  return (c->nb_read == 0
+	  || c->nb_read == c->size
+	  || (c->line_start_idx >= c->nb_read - 1));
+}
+
+/*  Return TRUE iff the cache is full and thus needs to be
+    extended.  */
+
+static bool
+needs_grow (fcache *c)
+{
+  return c->nb_read == c->size;
+}
+
+/* Grow the cache if it needs to be extended.  */
+
+static void
+maybe_grow (fcache *c)
+{
+  if (!needs_grow (c))
+    return;
+
+  size_t size = c->size == 0 ? fcache_buffer_size : c->size * 2;
+  c->data = XRESIZEVEC (char, c->data, size + 1);
+  c->size = size;
+}
+
+/*  Read more data into the cache.  Extends the cache if need be.
+    Returns TRUE iff new data could be read.  */
+
+static bool
+read_data (fcache *c)
 {
-  static char *string;
-  static size_t string_len;
-  size_t pos = 0;
-  char *ptr;
+  if (feof (c->fp) || ferror (c->fp))
+    return false;
+
+  maybe_grow (c);
+
+  char * from = c->data + c->nb_read;
+  size_t to_read = c->size - c->nb_read;
+  if (ferror (c->fp))
+    return false;
+  size_t nb_read = fread (from, 1, to_read, c->fp);
+
+  if (ferror (c->fp))
+    return false;
 
-  if (!string_len)
+  c->nb_read += nb_read;
+  return !!nb_read;
+}
+
+/* Read new data iff the cache needs to be filled with more data
+   coming from the file FP.  Return TRUE iff the cache was filled with
+   mode data.  */
+
+static bool
+maybe_read_data (fcache *c)
+{
+  if (!needs_read (c))
+    return false;
+  return read_data (c);
+}
+
+/* Read a new line from file FP, using C as a cache for the data
+   coming from the file.  Upon successful completion, *LINE is set to
+   the beginning of the line found.  Space for that line has been
+   allocated in the cache thus *LINE has the same life time as C.
+   This function returns the length of the line, including the
+   terminal '\n' character.  Note that subsequent calls to
+   get_next_line return the next lines of the file and might overwrite
+   the content of *LINE.  */
+
+static ssize_t
+get_next_line (fcache *c, char **line)
+{
+  /* Fill the cache with data to process.  */
+  maybe_read_data (c);
+
+  size_t remaining_size = c->nb_read - c->line_start_idx;
+  if (remaining_size == 0)
+    /* There is no more data to process.  */
+    return 0;
+
+  char *line_start = c->data + c->line_start_idx;
+
+  char *next_line_start = NULL;
+  size_t line_len = 0;
+  char *line_end = (char *) memchr (line_start, '\n', remaining_size);
+  if (line_end == NULL)
+    {
+      /* We haven't found the end-of-line delimiter in the cache.
+	 Fill the cache with more data from the file and look for the
+	 '\n'.  */
+      while (maybe_read_data (c))
+	{
+	  line_start = c->data + c->line_start_idx;
+	  remaining_size = c->nb_read - c->line_start_idx;
+	  line_end = (char *) memchr (line_start, '\n', remaining_size);
+	  if (line_end != NULL)
+	    {
+	      next_line_start = line_end + 1;
+	      line_len = line_end - line_start + 1;
+	      break;
+	    }
+	}
+      if (line_end == NULL)
+	{
+	  /* We've loadded all the file into the cache and still no
+	     '\n'.  Let's say the line ends up at the byte after the
+	     last byte of the file.  */
+	  line_end = c->data + c->nb_read;
+	  line_len = c->nb_read - c->line_start_idx;
+	}
+    }
+  else
     {
-      string_len = 200;
-      string = XNEWVEC (char, string_len);
+      next_line_start = line_end + 1;
+      line_len = line_end - line_start + 1;;
     }
 
-  while ((ptr = fgets (string + pos, string_len - pos, file)))
+  if (ferror (c->fp))
+    return -1;
+
+  /* At this point, we've found the end of the of line.  It either
+     points to the '\n' or to one byte after the last byte of the
+     file.  */
+  gcc_assert (line_end != NULL);
+
+  if (c->line_start_idx < c->nb_read)
+    *line = line_start;
+
+  gcc_assert (line_len > 0);
+
+  ++c->line_num;
+
+  /* Now update our line record so that re-reading lines from the
+     before c->line_start_idx is faster.  */
+  if (c->line_record.length () < fcache_line_record_size)
     {
-      size_t len = strlen (string + pos);
+      /* If the the file lines fits in the line record, we just record
+	 all its lines ...*/
+      if (c->total_lines <= fcache_line_record_size
+	  && c->line_num > c->line_record.length ())
+	c->line_record.safe_push (fcache::line_info (c->line_num,
+						 c->line_start_idx,
+						 line_end - c->data));
+      else if (c->total_lines > fcache_line_record_size)
+	{
+	  /* ... otherwise, we just scale total_lines down to
+	     (fcache_line_record_size lines.  */
+	  size_t n = (c->line_num * fcache_line_record_size) / c->total_lines;
+	  if (c->line_record.length () == 0
+	      || n >= c->line_record.length ())
+	    c->line_record.safe_push (fcache::line_info (c->line_num,
+						     c->line_start_idx,
+						     line_end - c->data));
+	}
+    }
+
+  /* Update c->line_start_idx so that it points to the next line to be
+     read.  */
+  if (next_line_start)
+    c->line_start_idx = next_line_start - c->data;
+  else
+    /* We didn't find any terminal '\n'.  Let's consider that the end
+       of line is the end of the data in the cache.  The next
+       invocation of get_next_line will either read more data from the
+       underlying file or return false early because we've reached the
+       end of the file.  */
+    c->line_start_idx = c->nb_read;
+
+  return line_len;
+}
+
+/* Reads the next line from FILE into *LINE.  If *LINE is too small
+   (or NULL) it is allocated (or extended) to have enough space to
+   containe the line.  *LINE_LENGTH must contain the size of the
+   initial*LINE buffer.  It's then updated by this function to the
+   actual length of the returned line.  Note that the returned line
+   can contain several zero bytes.  Also note that the returned string
+   is allocated in static storage that is going to be re-used by
+   subsequent invocations of read_line.  */
+
+static bool
+read_next_line (fcache *cache, char ** line, ssize_t *line_len)
+{
+  char *l = NULL;
+  ssize_t len = get_next_line (cache, &l);
+
+  if (len > 0)
+    {
+      if (*line == NULL)
+	{
+	  *line = XNEWVEC (char, len);
+	  *line_len = len;
+	}
+      else
+	if (*line_len < len)
+	  *line = XRESIZEVEC (char, *line, len);
+
+      memmove (*line, l, len);
+      (*line)[len - 1] = '\0';
+      *line_len = --len;
+      return true;
+    }
+
+  return false;
+}
 
-      if (string[pos + len - 1] == '\n')
+/* Consume the next bytes coming from the cache (or from its
+   underlying file if there are remaining unread bytes in the file)
+   until we reach the next end-of-line (or end-of-file).  There is no
+   copying from the cache involved.  Return TRUE upon successful
+   completion.  */
+
+static bool
+goto_next_line (fcache *cache)
+{
+  char *l = NULL;
+  ssize_t len = get_next_line (cache, &l);
+  return (len > 0 );
+}
+
+/* Read an arbitrary line number LINE_NUM from the file cached in C.
+   The line is copied into *LINE.  *LINE_LEN must have been set to the
+   length of *LINE.  If *LINE is too small (or NULL) it's extended (or
+   allocated) and *LINE_LEN is adjusted accordingly.  *LINE ends up
+   with a terminal zero byte and can contain additional zero bytes.
+   This function returns bool if a line was read.  */
+
+static bool
+read_line_num (fcache *c, size_t line_num,
+	       char ** line, ssize_t *line_len)
+{
+  gcc_assert (line_num > 0);
+
+  if (line_num <= c->line_num)
+    {
+      /* We've been asked to read lines that are before c->line_num.
+	 So lets use our line record (if it's not empty) to try to
+	 avoid re-reading the file from the beginning again.  */
+
+      if (c->line_record.is_empty ())
+	{
+	  c->line_start_idx = 0;
+	  c->line_num = 0;
+	}
+      else
 	{
-	  string[pos + len - 1] = 0;
-	  return string;
+	  fcache::line_info *i = NULL;
+	  if (c->total_lines <= fcache_line_record_size)
+	    {
+	      /*  Every line we've read has its start/end recorded
+		  here.  So this is going to be fast.  */
+	      gcc_assert (line_num <= c->total_lines);
+	      i = &c->line_record[line_num - 1];
+	      gcc_assert (i->line_num == line_num);
+	    }
+	  else
+	    {
+	      /*  So the file had more lines than our line record
+		  size.  Thus the number of lines we've recorded has
+		  been scaled down to fcache_line_reacord_size.  Let's
+		  pick the start/end of the recorded line that is
+		  closest to line_num.  */
+	      size_t n = line_num * fcache_line_record_size / c->total_lines;
+	      if (n < c->line_record.length ())
+		{
+		  i = &c->line_record[n];
+		  gcc_assert (i->line_num <= line_num);
+		}
+	    }
+
+	  if (i && i->line_num == line_num)
+	    {
+	      /* We have the start/end of the line.  Let's just copy
+		 it again and we are done.  */
+	      ssize_t len = i->end_pos - i->start_pos + 1;
+	      if (*line_len < len)
+		*line = XRESIZEVEC (char, *line, len);
+	      memmove (*line, c->data + i->start_pos, len);
+	      (*line)[len - 1] = '\0';
+	      *line_len = --len;
+	      return true;
+	    }
+
+	  if (i)
+	    {
+	      c->line_start_idx = i->start_pos;
+	      c->line_num = i->line_num - 1;
+	    }
+	  else
+	    {
+	      c->line_start_idx = 0;
+	      c->line_num = 0;
+	    }
 	}
-      pos += len;
-      string = XRESIZEVEC (char, string, string_len * 2);
-      string_len *= 2;
     }
-      
-  return pos ? string : NULL;
+
+  /*  Let's walk from line c->line_num up to line_num - 1, without
+      copying any line.  */
+  while (c->line_num < line_num - 1)
+    if (!goto_next_line (c))
+      return false;
+
+  /* The line we want is the next one.  Let's read and copy it back to
+     the caller.  */
+  return read_next_line (c, line, line_len);
 }
 
 /* Return the physical source line that corresponds to xloc in a
    buffer that is statically allocated.  The newline is replaced by
-   the null character.  */
+   the null character.  Note that the line can contain several null
+   characters, so LINE_LEN, if non-null, points to the actual length
+   of the line.  */
 
 const char *
-location_get_source_line (expanded_location xloc)
+location_get_source_line (expanded_location xloc,
+			  int *line_len)
 {
-  const char *buffer;
-  int lines = 1;
-  FILE *stream = xloc.file ? fopen (xloc.file, "r") : NULL;
-  if (!stream)
-    return NULL;
+  static char *buffer;
+  static ssize_t len;
+
+  fcache * c = lookup_or_add_file_to_cache_tab (xloc.file);
+  bool read = read_line_num (c, xloc.line, &buffer, &len);
 
-  while ((buffer = read_line (stream)) && lines < xloc.line)
-    lines++;
+  if (read && line_len)
+    *line_len = len;
 
-  fclose (stream);
-  return buffer;
+  return read ? buffer : NULL;
 }
 
 /* Expand the source location LOC into a human readable location.  If
diff --git a/gcc/input.h b/gcc/input.h
index 8fdc7b2..c82023f 100644
--- a/gcc/input.h
+++ b/gcc/input.h
@@ -37,7 +37,8 @@ extern char builtins_location_check[(BUILTINS_LOCATION
 				     < RESERVED_LOCATION_COUNT) ? 1 : -1];
 
 extern expanded_location expand_location (source_location);
-extern const char *location_get_source_line (expanded_location xloc);
+extern const char *location_get_source_line (expanded_location xloc,
+					     int *line_size);
 extern expanded_location expand_location_to_spelling_point (source_location);
 extern source_location expansion_point_location_if_in_system_header (source_location);
 
@@ -65,4 +66,6 @@ extern location_t input_location;
 
 void dump_line_table_statistics (void);
 
+void diagnostics_file_cache_fini (void);
+
 #endif
diff --git a/gcc/testsuite/c-c++-common/cpp/warning-zero-in-literals-1.c b/gcc/testsuite/c-c++-common/cpp/warning-zero-in-literals-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..ff2ed962ac96e47ae05b0b040f4e10b8e09637e2
GIT binary patch
literal 240
zcmdPbSEyD<N!LxuS12e-Ehx%QPAx80sO92PVo*}h*HVDUmM0eFW#*+TDCL#r<R~O(
UBo-wmm!uXcDby-x=?^KT09Xk|)&Kwi

literal 0
HcmV?d00001

diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index a0d6da1..3504fd6 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -756,6 +756,14 @@ struct linemap_stats
   long duplicated_macro_maps_locations_size;
 };
 
+/* Return the highest location emitted for a given file for which
+   there is a line map in SET.  FILE_NAME is the file name to
+   consider.  If the function returns TRUE, *LOC is set to the highest
+   location emitted for that file.  */
+bool linemap_get_file_highest_location (struct line_maps * set,
+					const char *file_name,
+					source_location*LOC);
+
 /* Compute and return statistics about the memory consumption of some
    parts of the line table SET.  */
 void linemap_get_statistics (struct line_maps *, struct linemap_stats *);
diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index 2ad7ad2..3c0f74d 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -1502,6 +1502,46 @@ linemap_dump_location (struct line_maps *set,
 	   path, from, l, c, s, (void*)map, e, loc, location);
 }
 
+/* Return the highest location emitted for a given file for which
+   there is a line map in SET.  FILE_NAME is the file name to
+   consider.  If the function returns TRUE, *LOC is set to the highest
+   location emitted for that file.  */
+
+bool
+linemap_get_file_highest_location (struct line_maps *set,
+				   const char *file_name,
+				   source_location *loc)
+{
+  /* If the set is empty or no ordinary map has been created then
+     there is no file to look for ...  */
+  if (set == NULL || set->info_ordinary.used == 0)
+    return false;
+
+  /* Now look for the last ordinary map created for FILE_NAME.  */
+  int i;
+  for (i = set->info_ordinary.used - 1; i >= 0; --i)
+    {
+      const char *fname = set->info_ordinary.maps[i].d.ordinary.to_file;
+      if (fname && !strcmp (fname, file_name))
+	break;
+    }
+
+  if (i < 0)
+    return false;
+
+  /* The highest location for a given map is either the starting
+     location of the next map minus one, or -- if the map is the
+     latest one -- the highest location of the set.  */
+  source_location result;
+  if (i == (int) set->info_ordinary.used - 1)
+    result = set->highest_location;
+  else
+    result = set->info_ordinary.maps[i].start_location - 1;
+
+  *loc = result;
+  return true;
+}
+
 /* Compute and return statistics about the memory consumption of some
    parts of the line table SET.  */
 
-- 
                        Dodji