1 files changed, 9 insertions, 14 deletions

diff --git a/src/doprnt.c b/src/doprnt.c
index 195598c07ea..79f9f36e461 100644
--- a/src/doprnt.c
+++ b/src/doprnt.c
@@ -102,13 +102,8 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <stdio.h>
 #include <ctype.h>
 #include <setjmp.h>
-
-#ifdef STDC_HEADERS
 #include <float.h>
-#endif
-
 #include <unistd.h>
-
 #include <limits.h>
 
 #include "lisp.h"
@@ -134,8 +129,8 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    String arguments are passed as C strings.
    Integers are passed as C integers.  */
 
-size_t
-doprnt (char *buffer, register size_t bufsize, const char *format,
+ptrdiff_t
+doprnt (char *buffer, ptrdiff_t bufsize, const char *format,
         const char *format_end, va_list ap)
 {
   const char *fmt = format;     /* Pointer into format string */
@@ -145,7 +140,7 @@ doprnt (char *buffer, register size_t bufsize, const char *format,
   char tembuf[DBL_MAX_10_EXP + 100];
 
   /* Size of sprintf_buffer.  */
-  size_t size_allocated = sizeof (tembuf);
+  ptrdiff_t size_allocated = sizeof (tembuf);
 
   /* Buffer to use for sprintf.  Either tembuf or same as BIG_BUFFER.  */
   char *sprintf_buffer = tembuf;
@@ -164,7 +159,7 @@ doprnt (char *buffer, register size_t bufsize, const char *format,
   if (format_end == 0)
     format_end = format + strlen (format);
 
-  if ((format_end - format + 1) < sizeof (fixed_buffer))
+  if (format_end - format < sizeof (fixed_buffer) - 1)
     fmtcpy = fixed_buffer;
   else
     SAFE_ALLOCA (fmtcpy, char *, format_end - format + 1);
@@ -176,7 +171,7 @@ doprnt (char *buffer, register size_t bufsize, const char *format,
     {
       if (*fmt == '%')  /* Check for a '%' character */
         {
-          size_t size_bound = 0;
+          ptrdiff_t size_bound = 0;
           EMACS_INT width;  /* Columns occupied by STRING on display.  */
           int long_flag = 0;
           int pIlen = sizeof pI - 1;
@@ -194,16 +189,16 @@ doprnt (char *buffer, register size_t bufsize, const char *format,
                      This might be a field width or a precision; e.g.
                      %1.1000f and %1000.1f both might need 1000+ bytes.
                      Parse the width or precision, checking for overflow.  */
-                  size_t n = *fmt - '0';
+                  ptrdiff_t n = *fmt - '0';
                   while (fmt + 1 < format_end
                          && '0' <= fmt[1] && fmt[1] <= '9')
                     {
-                      /* Avoid size_t overflow.  Avoid int overflow too, as
+                      /* Avoid ptrdiff_t, size_t, and int overflow, as
                          many sprintfs mishandle widths greater than INT_MAX.
                          This test is simple but slightly conservative: e.g.,
                          (INT_MAX - INT_MAX % 10) is reported as an overflow
                          even when it's not.  */
-                      if (n >= min (INT_MAX, SIZE_MAX) / 10)
+                      if (n >= min (INT_MAX, min (PTRDIFF_MAX, SIZE_MAX)) / 10)
                         error ("Format width or precision too large");
                       n = n * 10 + fmt[1] - '0';
                       *string++ = *++fmt;
@@ -235,7 +230,7 @@ doprnt (char *buffer, register size_t bufsize, const char *format,
 
           /* Make the size bound large enough to handle floating point formats
              with large numbers.  */
-          if (size_bound > SIZE_MAX - DBL_MAX_10_EXP - 50)
+          if (size_bound > min (PTRDIFF_MAX, SIZE_MAX) - DBL_MAX_10_EXP - 50)
             error ("Format width or precision too large");
           size_bound += DBL_MAX_10_EXP + 50;