Re: [COMMIT] Increase READ_BUF_SIZE, used in #'insert-file-contents-internal, to #x10000

 Ar an séú lá déag de mí Eanair, scríobh Jerry James: 

 > On Thu, Jan 16, 2014 at 1:39 PM, Aidan Kehoe <[email protected]> wrote:
 > >
 > > -/* Stack sizes > 2**16 is a good way to elicit compiler bugs */
 > > -/* #define READ_BUF_SIZE (2 << 16) */
 > > -#define READ_BUF_SIZE (1 << 15)
 > > +#define READ_BUF_SIZE (2 << 16)
 > >
 > 
 > (2 << 16) != 2**16 == #x10000.  That would be (1 << 16); what you have
 > there is 2**17 == #x20000.

That is an odd size for the original code! My mistake, indeed, though it
works fine and is even better for my use case than #x10000. What about the
following, since alloca_* is more careful about not blowing the stack, and
its use shows better intentionality? (Though both buffers actually remain on
the stack, with current thresholds.)

diff -r 580ebed3500a src/fileio.c
--- a/src/fileio.c	Sat Jan 18 17:40:41 2014 +0100
+++ b/src/fileio.c	Sat Jan 18 18:34:37 2014 +0000
@@ -1803,7 +1803,7 @@
 {
   /* This function can call Lisp.  GC checked 2000-07-28 ben */
   int ifd, ofd, n;
-  Rawbyte buf[READ_BUF_SIZE];
+  Rawbyte *buf = alloca_rawbytes (READ_BUF_SIZE);
   struct stat st, out_st;
   Lisp_Object handler;
   int speccount = specpdl_depth ();
@@ -1909,7 +1909,7 @@
 
     record_unwind_protect (close_file_unwind, ofd_locative);
 
-    while ((n = read_allowing_quit (ifd, buf, sizeof (buf))) > 0)
+    while ((n = read_allowing_quit (ifd, buf, READ_BUF_SIZE)) > 0)
     {
       if (write_allowing_quit (ofd, buf, n) != n)
 	report_file_error ("I/O error", newname);
@@ -2899,7 +2899,7 @@
   struct gcpro gcpro1, gcpro2, gcpro3, gcpro4;
   Lisp_Object val;
   int total;
-  Ibyte read_buf[READ_BUF_SIZE];
+  Ibyte *read_buf = alloca_ibytes (READ_BUF_SIZE);
   int mc_count;
   struct buffer *buf = current_buffer;
   Lisp_Object curbuf;
@@ -3199,8 +3199,7 @@
 	Charcount cc_inserted, this_tell = last_tell;
 
 	QUIT;
-	this_len = Lstream_read (XLSTREAM (stream), read_buf,
-				 sizeof (read_buf));
+	this_len = Lstream_read (XLSTREAM (stream), read_buf, READ_BUF_SIZE);
 
 	if (this_len <= 0)
 	  {

-- 
‘Liston operated so fast that he once accidentally amputated an assistant’s
fingers along with a patient’s leg, […] The patient and the assistant both
died of sepsis, and a spectator reportedly died of shock, resulting in the
only known procedure with a 300% mortality.’ (Atul Gawande, NEJM, 2012)

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