avoid storing pointer diff in an int

The distance between endb and next was being stored in an int variable. While
this should not exceed the bounds of an int during normal usage, it's risky to
store a pointer difference in a narrower type this way.

diff --git a/lib/sfio/sfmode.c b/lib/sfio/sfmode.c
index 1339b7f3076381a25f68b4297d4bc3424de89485..f080efa6503b1ba36381160b15d57a614554c32f 100644 (file)
--- a/lib/sfio/sfmode.c
+++ b/lib/sfio/sfmode.c
@@ -12,6 +12,7 @@
  *************************************************************************/
 
 #include       <sfio/sfhdr.h>
+#include <stdint.h>
 static char *Version = "\n@(#)sfio (AT&T Labs - kpv) 2001-02-01\0\n";
 
 /*     Functions to set a given stream to some desired mode
@@ -300,7 +301,6 @@ static int _sfpmode(Sfio_t * f, int type)
  */
 int _sfmode(reg Sfio_t * f, reg int wanted, reg int local)
 {
-    reg int n;
     Sfoff_t addr;
     reg int rv = 0;
 
@@ -381,7 +381,7 @@ int _sfmode(reg Sfio_t * f, reg int wanted, reg int local)
            else
                f->endw = f->endb;
        } else {
-           n = f->flags;
+           unsigned short n = f->flags;
            (void) SFSETBUF(f, f->data, f->size);
            f->flags |= (n & SF_MALLOC);
        }
@@ -458,7 +458,7 @@ int _sfmode(reg Sfio_t * f, reg int wanted, reg int local)
 
        /* reset buffer and seek pointer */
        if (!(f->mode & SF_SYNCED)) {
-           n = f->endb - f->next;
+           intptr_t n = (intptr_t)(f->endb - f->next);
            if (f->extent >= 0 && (n > 0 || (f->data && (f->bits & SF_MMAP)))) {        /* reset file pointer */
                addr = f->here - n;
                if (SFSK(f, addr, SEEK_SET, f->disc) < 0)