PATCH: Allocate sufficient space for string buffer

[H.J. Lu]

On Thu, Jun 7, 2012 at 9:16 PM, Alan Modra <amodra@gmail.com> wrote:
> On Thu, Jun 07, 2012 at 08:08:13PM -0700, H.J. Lu wrote:
>> -  sb_new (&from_sb);
>> +  /* Allocate sufficient space: from->len + optional newline + '\0'.  */
>> +  newline = from->len >= 1 && from->ptr[0] != '\n';
>> +  sb_build (&from_sb, from->len + newline + 1);
>
> No, please look at sb_build!  It already adds one for the terminator.

The extra 1 byte is for

  /* Make sure the parser looks at defined contents when it scans for
     e.g. end-of-line at the end of a macro.  */
  sb_add_char (&from_sb, 0);

since we have

sb_add_char (&from_sb, '\n');
sb_scrub_and_add_sb (&from_sb, from);
sb_add_char (&from_sb, 0);

That is from->len + newline + 1 bytes.

Here is a new patch which also replaces all

sb_new
...
sb_kill

with

sb_build
...
sb_kill

-- 
H.J.
---
2012-06-08  H.J. Lu  <hongjiu.lu@intel.com>

	* input-scrub.c (input_scrub_include_sb): Use sb_build to
	allocate sufficient space for from_sb.
	* read.c (read_a_source_file): Use sb_build to allocate
	sufficient space and replace sb_add_string with sb_add_buffer.
	(s_macro): Likewise.
	(input_scrub_insert_line): Likewise.
	(s_irp): Use sb_build to allocate sufficient space.
	(do_repeat): Use sb_build to allocate sufficient space
	for many.
	* sb.c (sb_build): Remove static.
	(sb_check): Increase max size by dsize only if needed.
	* sb.h (sb_build): New prototype.

diff --git a/gas/input-scrub.c b/gas/input-scrub.c
index 46dd244..1b09b73 100644
--- a/gas/input-scrub.c
+++ b/gas/input-scrub.c
@@ -264,6 +264,8 @@ input_scrub_include_file (char *filename, char *position)
 void
 input_scrub_include_sb (sb *from, char *position, int is_expansion)
 {
+  int newline;
+
   if (macro_nest > max_macro_nest)
     as_fatal (_("macros nested too deeply"));
   ++macro_nest;
@@ -277,9 +279,11 @@ input_scrub_include_sb (sb *from, char *position,
int is_expansion)

   next_saved_file = input_scrub_push (position);

-  sb_new (&from_sb);
+  /* Allocate sufficient space: from->len + optional newline + '\0'.  */
+  newline = from->len >= 1 && from->ptr[0] != '\n';
+  sb_build (&from_sb, from->len + newline + 1);
   from_sb_is_expansion = is_expansion;
-  if (from->len >= 1 && from->ptr[0] != '\n')
+  if (newline)
     {
       /* Add the sentinel required by read.c.  */
       sb_add_char (&from_sb, '\n');
diff --git a/gas/read.c b/gas/read.c
index 2b37173..21c42b2 100644
--- a/gas/read.c
+++ b/gas/read.c
@@ -1181,7 +1181,6 @@ read_a_source_file (char *name)
 	      bump_line_counters ();
 	      s += 4;

-	      sb_new (&sbuf);
 	      ends = strstr (s, "#NO_APP\n");

 	      if (!ends)
@@ -1262,7 +1261,9 @@ read_a_source_file (char *name)
 		 actual macro expansion (possibly nested) and other
 		 input expansion work.  Beware that in messages, line
 		 numbers and possibly file names will be incorrect.  */
-	      sb_add_string (&sbuf, new_buf);
+	      new_length = strlen (new_buf);
+	      sb_build (&sbuf, new_length);
+	      sb_add_buffer (&sbuf, new_buf, new_length);
 	      input_scrub_include_sb (&sbuf, input_line_pointer, 0);
 	      sb_kill (&sbuf);
 	      buffer_limit = input_scrub_next_buffer (&input_line_pointer);
@@ -2437,8 +2438,8 @@ s_irp (int irpc)

   as_where (&file, &line);

-  sb_new (&s);
   eol = find_end_of_line (input_line_pointer, 0);
+  sb_build (&s, eol - input_line_pointer);
   sb_add_buffer (&s, input_line_pointer, eol - input_line_pointer);
   input_line_pointer = eol;

@@ -2773,17 +2774,20 @@ s_macro (int ignore ATTRIBUTE_UNUSED)

   as_where (&file, &line);

-  sb_new (&s);
   eol = find_end_of_line (input_line_pointer, 0);
+  sb_build (&s, eol - input_line_pointer);
   sb_add_buffer (&s, input_line_pointer, eol - input_line_pointer);
   input_line_pointer = eol;

   if (line_label != NULL)
     {
       sb label;
+      size_t len;

-      sb_new (&label);
-      sb_add_string (&label, S_GET_NAME (line_label));
+      name = S_GET_NAME (line_label);
+      len = strlen (name);
+      sb_build (&label, len);
+      sb_add_buffer (&label, name, len);
       err = define_macro (0, &s, &label, get_macro_line_sb, file, line, &name);
       sb_kill (&label);
     }
@@ -3207,7 +3211,7 @@ do_repeat (int count, const char *start, const char *end)
       return;
     }

-  sb_new (&many);
+  sb_build (&many, count * one.len);
   while (count-- > 0)
     sb_add_sb (&many, &one);

@@ -3247,7 +3251,7 @@ do_repeat_with_expander (int count,
 	  char * sub;
 	  sb processed;

-	  sb_new (& processed);
+	  sb_build (& processed, one.len);
 	  sb_add_sb (& processed, & one);
 	  sub = strstr (processed.ptr, expander);
 	  len = sprintf (sub, "%d", count);
@@ -6167,8 +6171,9 @@ void
 input_scrub_insert_line (const char *line)
 {
   sb newline;
-  sb_new (&newline);
-  sb_add_string (&newline, line);
+  size_t len = strlen (line);
+  sb_build (&newline, len);
+  sb_add_buffer (&newline, line, len);
   input_scrub_include_sb (&newline, input_line_pointer, 0);
   sb_kill (&newline);
   buffer_limit = input_scrub_next_buffer (&input_line_pointer);
diff --git a/gas/sb.c b/gas/sb.c
index f345fe1..ebfd77f 100644
--- a/gas/sb.c
+++ b/gas/sb.c
@@ -44,7 +44,7 @@ static void sb_check (sb *, size_t);

 /* Initializes an sb.  */

-static void
+void
 sb_build (sb *ptr, size_t size)
 {
   ptr->ptr = xmalloc (size + 1);
@@ -116,7 +116,7 @@ sb_check (sb *ptr, size_t len)
 {
   size_t max = ptr->max;

-  while (ptr->len + len >= max)
+  while (ptr->len + len > max)
     {
       max <<= 1;
       if (max == 0)
diff --git a/gas/sb.h b/gas/sb.h
index cc11ef6..ea010ee 100644
--- a/gas/sb.h
+++ b/gas/sb.h
@@ -53,6 +53,7 @@ typedef struct sb
 sb;

 extern void sb_new (sb *);
+extern void sb_build (sb *, size_t);
 extern void sb_kill (sb *);
 extern void sb_add_sb (sb *, sb *);
 extern void sb_scrub_and_add_sb (sb *, sb *);