running the attached program on Linux (SuSE 9.2) results in purify UMR reports
as shown below.

I checked the sources for glibc 2.4 and it looks like in sysdeps/unix/opendir.c
the function __alloc_dir has some mismatch in malloc() and memset:

  DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation + pad);

.....

  memset (dirp, '\0', sizeof (DIR));


-------------------------------------------------------------
#include <sys/types.h>
#include <dirent.h>

#include <stdio.h>


int main(int argc, char** argv)
{
	DIR* d;
	struct dirent* e;

	d = opendir(".");
	if (d != NULL) {
		e = readdir(d);
		while (e != NULL) {
			printf("%s\n", e->d_name);
			e = readdir(d);
		}

		closedir(d);
	}
}

-------------------------------------------------------------

****  Purify instrumented ./a.out (pid 30822)  ****
UMR: Uninitialized memory read (311 times):
  * This is occurring while in:
        __getdents     [libc.so.6]
        readdir        [libc.so.6]
        main           [readdir.c:14]
        __libc_start_main [libc.so.6]
        _start         [crt1.o]
  * Reading 2 bytes from 0x80b405c in the heap.
  * Address 0x80b405c is 36 bytes into a malloc'd block at 0x80b4038 of 32796 bytes.
  * This block was allocated from:
        malloc         [rtlib.o]
        opendir        [libc.so.6]
        main           [readdir.c:12]
        __libc_start_main [libc.so.6]
        _start         [crt1.o]

------- Additional Comment #1 From Ulrich Drepper 2006-08-12 21:09 -------

The remainder of the buffer need not be initialized because it is just to store
the results of the getdents call and isn't read before the kernel fills it.