#16 expect is using memcpy where memmove is needed

[Per Cederqvist]

The ecases_remove_by_expi() function in expect.c uses memcpy() to shift elements down. The areas can be overlapping. When they are, the construct is non-portable and can lead to memory corruption.

Please replace the memcpy call with a memmove call. That fixes the issue.

This is a real problem. It causes expect to randomly crash when run on the LysKOM server testsuite on an x86_64 Linux system (Ubuntu 13.04, gcc 4.7.3). valgrind helped me track down the issue.

(The issue can be reproduced by running the test suite of https://git.lysator.liu.se/lyskom-server/lyskom-server. Be sure to instrument runtest so that it uses valgrind to invoce expect.)

[Per Cederqvist]

The enclosed file is a minimal example that demonstrates the issue. If you run it as "valgrind expect trigger2.expect", valgrind will report an error similar to:

==8467== Source and destination overlap in memcpy(0x60b9170, 0x60b9178, 16)
==8467==    at 0x4C2E820: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

The expect5.45-memmove.patch previoiusly attached to this issue fixes the problem.

[Andreas Kupries]

* exp_main_sub.c: Updated EXP_VERSION to 5.45.2
* configure, configure.in: Updated expect to version 5.45.2

* expect.c: [http://sourceforge.net/p/expect/patches/16/]. Report
  and fix both by Per Cederqvist. Replaced a memcpy with memmove
  as the latter properly handles overlapping memory, whereas the
  original code does not.

Committed to CVS.
Thank you for the report and fix.