(Fcall_process): Don't use alloca to gradually

increase size of buf, as it effectively uses twice the necessary
space on the stack.  Instead, pre-allocate buf of full size, and
gradually increase the read size.

diff --git a/src/callproc.c b/src/callproc.c
index 6027ccdda9f2dd9ebd9913221c382ef6fc79ce60..fe198b0770acc1e97a1f7fde6785c7e436dd7df7 100644 (file)
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -218,9 +218,10 @@ usage: (call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)  */)
   int fd[2];
   int filefd;
   register int pid;
-  char buf[16384];
-  char *bufptr = buf;
-  int bufsize = sizeof buf;
+#define CALLPROC_BUFFER_SIZE_MIN (16 * 1024)
+#define CALLPROC_BUFFER_SIZE_MAX (4 * CALLPROC_BUFFER_SIZE_MIN)
+  char buf[CALLPROC_BUFFER_SIZE_MAX];
+  int bufsize = CALLPROC_BUFFER_SIZE_MIN;
   int count = SPECPDL_INDEX ();
 
   register const unsigned char **new_argv
@@ -765,7 +766,7 @@ usage: (call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)  */)
        nread = carryover;
        while (nread < bufsize - 1024)
          {
-           int this_read = emacs_read (fd[0], bufptr + nread,
+           int this_read = emacs_read (fd[0], buf + nread,
                                        bufsize - nread);
 
            if (this_read < 0)
@@ -790,7 +791,7 @@ usage: (call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)  */)
        if (!NILP (buffer))
          {
            if (! CODING_MAY_REQUIRE_DECODING (&process_coding))
-             insert_1_both (bufptr, nread, nread, 0, 1, 0);
+             insert_1_both (buf, nread, nread, 0, 1, 0);
            else
              {                 /* We have to decode the input.  */
                int size;
@@ -807,7 +808,7 @@ usage: (call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)  */)
                   requires text-encoding detection.  */
                if (process_coding.type == coding_type_undecided)
                  {
-                   detect_coding (&process_coding, bufptr, nread);
+                   detect_coding (&process_coding, buf, nread);
                    if (process_coding.composing != COMPOSITION_DISABLED)
                      /* We have not yet allocated the composition
                         data because the coding type was undecided.  */
@@ -816,7 +817,7 @@ usage: (call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)  */)
                if (process_coding.cmp_data)
                  process_coding.cmp_data->char_offset = PT;
 
-               decode_coding (&process_coding, bufptr, decoding_buf,
+               decode_coding (&process_coding, buf, decoding_buf,
                               nread, size);
 
                if (display_on_the_fly
@@ -905,7 +906,7 @@ usage: (call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)  */)
                if (carryover > 0)
                  /* As CARRYOVER should not be that large, we had
                     better avoid overhead of bcopy.  */
-                 BCOPY_SHORT (bufptr + process_coding.consumed, bufptr,
+                 BCOPY_SHORT (buf + process_coding.consumed, buf,
                               carryover);
                if (process_coding.result == CODING_FINISH_INSUFFICIENT_CMP)
                  {
@@ -922,17 +923,13 @@ usage: (call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)  */)
        if (process_coding.mode & CODING_MODE_LAST_BLOCK)
          break;
 
+#if (CALLPROC_BUFFER_SIZE_MIN != CALLPROC_BUFFER_SIZE_MAX)
        /* Make the buffer bigger as we continue to read more data,
-          but not past 64k.  */
-       if (bufsize < 64 * 1024 && total_read > 32 * bufsize)
-         {
-           char *tempptr;
-           bufsize *= 2;
-
-           tempptr = (char *) alloca (bufsize);
-           bcopy (bufptr, tempptr, bufsize / 2);
-           bufptr = tempptr;
-         }
+          but not past CALLPROC_BUFFER_SIZE_MAX.  */
+       if (bufsize < CALLPROC_BUFFER_SIZE_MAX && total_read > 32 * bufsize)
+         if ((bufsize *= 2) > CALLPROC_BUFFER_SIZE_MAX)
+           bufsize = CALLPROC_BUFFER_SIZE_MAX;
+#endif
 
        if (display_p)
          {