d: Use read() to load contents of stdin into memory.

This would be an improvement over reading one character at a time.

An ICE was discovered when mixing reading from stdin with `-v', this has been
fixed in upstream DMD and backported as well.

Reviewed-on: https://github.com/dlang/dmd/pull/11620

gcc/d/ChangeLog:

	* d-lang.cc (d_parse_file): Use read() to load contents from stdin,
	allow the front-end to free the memory after parsing.
	* dmd/MERGE: Merge upstream dmd 2cc25c219.

1 files changed, 27 insertions, 16 deletions

diff --git a/gcc/d/d-lang.cc b/gcc/d/d-lang.cc
index 6183389..c5254a0 100644
--- a/gcc/d/d-lang.cc
+++ b/gcc/d/d-lang.cc
@@ -906,32 +906,43 @@ d_parse_file (void)
     {
       if (strcmp (in_fnames[i], "-") == 0)
 	{
-	  /* Handling stdin, generate a unique name for the module.  */
-	  obstack buffer;
-	  gcc_obstack_init (&buffer);
-	  int c;
+	  /* Load the entire contents of stdin into memory.  8 kilobytes should
+	     be a good enough initial size, but double on each iteration.
+	     16 bytes are added for the final '\n' and 15 bytes of padding.  */
+	  ssize_t size = 8 * 1024;
+	  uchar *buffer = XNEWVEC (uchar, size + 16);
+	  ssize_t len = 0;
+	  ssize_t count;
+
+	  while ((count = read (STDIN_FILENO, buffer + len, size - len)) > 0)
+	    {
+	      len += count;
+	      if (len == size)
+		{
+		  size *= 2;
+		  buffer = XRESIZEVEC (uchar, buffer, size + 16);
+		}
+	    }
 
+	  if (count < 0)
+	    {
+	      error (Loc ("stdin", 0, 0), "%s", xstrerror (errno));
+	      free (buffer);
+	      continue;
+	    }
+
+	  /* Handling stdin, generate a unique name for the module.  */
 	  Module *m = Module::create (in_fnames[i],
 				      Identifier::generateId ("__stdin"),
 				      global.params.doDocComments,
 				      global.params.doHdrGeneration);
 	  modules.push (m);
 
-	  /* Load the entire contents of stdin into memory.  */
-	  while ((c = getc (stdin)) != EOF)
-	    obstack_1grow (&buffer, c);
-
-	  if (!obstack_object_size (&buffer))
-	    obstack_1grow (&buffer, '\0');
-
 	  /* Overwrite the source file for the module, the one created by
 	     Module::create would have a forced a `.d' suffix.  */
 	  m->srcfile = File::create ("<stdin>");
-	  m->srcfile->len = obstack_object_size (&buffer);
-	  m->srcfile->buffer = (unsigned char *) obstack_finish (&buffer);
-
-	  /* Tell the front-end not to free the buffer after parsing.  */
-	  m->srcfile->ref = 1;
+	  m->srcfile->len = len;
+	  m->srcfile->buffer = buffer;
 	}
       else
 	{