Python 3.1.3 fails to build on HP-UX/PA:
In file included from /opt/build/Python-3.1.3/Modules/_ctypes/libffi/src/dlmalloc.c:1156:
/opt/TWWfsw/gcc42/lib/gcc/hppa2.0-hp-hpux11.31/4.2/include/stdlib.h:577: error: redefinition of 'struct mallinfo'

Failed to build these modules:
_ctypes

<stdlib.h> on HP-UX has a conflicting definition for struct mallinfo:
#ifndef _STRUCT_MALLINFO
#  define _STRUCT_MALLINFO

  /* structure filled by mallinfo */
  struct mallinfo  {
        int32_t arena;          /* total number of bytes in arena */
        int32_t ordblks;        /* number of ordinary blocks */
        int32_t smblks;         /* number of small blocks */
        int32_t hblks;          /* number of holding blocks */
        int32_t hblkhd;         /* number of bytes in holding block headers */
        int32_t usmblks;        /* number of bytes in small blocks in use */
        int32_t fsmblks;        /* number of bytes in free small blocks */
        int32_t uordblks;       /* number of bytes in ordinary blocks in use */
        int32_t fordblks;       /* number of bytes in free ordinary blocks */
        int32_t keepcost;       /* cost of enabling keep option */
  };    
#endif /* _STRUCT_MALLINFO */

I confirm that on Python 2.7.1, on HP-UX 11.31, ia64 architecture).

dlmalloc.c is the problematic file, a part of libffi.

I reported the same problem and solution + patch in here:
http://sourceware.org/ml/libffi-discuss/2010/msg00203.html

quick update: libffi (upstream) has this fixed now in git commit dc411e8f991 .

Surely this can't be a problem nearly four years on?

> quick update: libffi (upstream) has this fixed now in git commit dc411e8f991 .

https://github.com/atgreen/libffi/commit/dc411e8f991

This commit was in Python since at least Python 3.3. It also part of the development branch of Python 2.7. I'm too lazy to check was exact version included the fix, but the issue was closed.

(See maybe also issue #18178 and #3526.)