POSIX::strftime buffer overflow problem

Message-Id: <199901271954.OAA07391@dcm2.cibcwg.com>

p4raw-id: //depot/cfgperl@2797

diff --git a/ext/POSIX/POSIX.xs b/ext/POSIX/POSIX.xs
index c948cc6..ae88aef 100644 (file)
--- a/ext/POSIX/POSIX.xs
+++ b/ext/POSIX/POSIX.xs
@@ -3631,7 +3631,41 @@ strftime(fmt, sec, min, hour, mday, mon, year, wday = -1, yday = -1, isdst = -1)
            mytm.tm_isdst = isdst;
            (void) mktime(&mytm);
            len = strftime(tmpbuf, sizeof tmpbuf, fmt, &mytm);
-           ST(0) = sv_2mortal(newSVpv(tmpbuf, len));
+           /*
+           ** The following is needed to handle to the situation where 
+           ** tmpbuf overflows.  Basically we want to allocate a buffer
+           ** and try repeatedly.  The reason why it is so complicated
+           ** is that getting a return value of 0 from strftime can indicate
+           ** one of the following:
+           ** 1. buffer overflowed,
+           ** 2. illegal conversion specifier, or
+           ** 3. the format string specifies nothing to be returned(not
+           **    an error).  This could be because format is an empty string
+           **    or it specifies %p that yields an empty string in some locale.
+           ** If there is a better way to make it portable, go ahead by
+           ** all means.
+           */
+           if ( ( len > 0 && len < sizeof(tmpbuf) )
+                       || ( len == 0 && strlen(fmt) == 0 ) ) {
+               ST(0) = sv_2mortal(newSVpv(tmpbuf, len));
+           } else {
+               /* Possibly buf overflowed - try again with a bigger buf */
+               int     bufsize = strlen(fmt) + sizeof(tmpbuf);
+               char*   buf = safemalloc(bufsize);
+               int     buflen;
+               while( buf ) {
+                   buflen = strftime(buf, bufsize, fmt, &mytm);
+                   if ( buflen > 0 && buflen < bufsize ) break;
+                   bufsize *= 2;
+                   buf = saferealloc(buf, bufsize);
+               }
+               if ( buf ) {
+                   ST(0) = sv_2mortal(newSVpv(buf, buflen));
+                   safefree(buf);
+               } else {
+                   ST(0) = sv_2mortal(newSVpv(tmpbuf, len));
+               }
+           }
        }
 
 void