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Date: Wed, 15 Mar 2006 14:39:45 -0600
From: Paul Mattes <paul DOT mattes AT usa DOT net>
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Subject: Memory leak in vsnprintf
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I believe I have found a memory leak in the Cygwin version of 
vsnprintf().  If it is called with a NULL 'str' parameter and a 0 
'length', it leaks a BUFSIZ-sized buffer.  (Per C99 and SUSv3, calling 
vsnprintf() with a NULL 'str' and 0 'length' is a way to find out how 
big the formatted string would be without actually storing it anywhere.)

I see that Cygwin's vsnprintf() comes from newlib.  Should I report this 
to them instead?

Here is an example program:

    #include <stdio.h>
    #include <stdarg.h>

    int
    waste_it(char *fmt, ...)
    {
            int ns;
            va_list a;

            va_start(a, fmt);
            ns = vsnprintf(NULL, 0, fmt, a);
            va_end(a);
            return ns;
    }

    main(int argc, char *argv[])
    {
            int i;
            int n;

            for (i = 0; i < 10000; i++) {
                    n += waste_it("%s foo %d", "hello", 49);
            }
    }

This program will consume quite a lot of memory on Cygwin.

-- 
        pdm


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