Windows C environment does not offer ssize_t type out of the box. Therefore the nghhtp2 library offers to define it in the compiler flags like:

CFLAGS = ... -Dssize_t=long ...

This is a questionable way to go for a number of reasons:

• Definition of the data type in the compilation command complicates use of the library in software development: one should not forget to define ssize_t in the same way, which is pretty inconvenient and not flexible;
• Although ssize_t is not defined out of the box on Windows, it is too well known type name to define it in a specific library: a chance of conflict with other code is high;
• Finally, definition of ssize_t as long does not look correct for 64-bit builds; sizeof(long) is 4 for 64-bit Windows while 8-byte data would be more appropriate. Windows introduces SSIZE_T type though.

Looks like the best solution would be introduction of a kind of nghhtp2_ssize_t type, which would be properly typedef'ed for each platform flavor. As a quick workaround, the following method works:

1. The Windows complication flags (locally for the library build only) are changed to

CFLAGS = ... -Dssize_t=SSIZE_T ...

2. The following code is added to file 'includes/nghttp2/nghttp2.h' (line ~32; after ensuring WIN32 is defined):

   #if defined(WIN32)
   #  pragma once
   #  include <basetsd.h>
   typedef SSIZE_T NGHTTP2_SSIZE_T;
   #  if !defined(BUILDING_NGHTTP2)
   #    define ssize_t NGHTTP2_SSIZE_T
   #  endif
   #endif

3. The following code is added to file 'includes/nghttp2/nghttp2.h' (line ~4965; before the final #endif):

   #if defined(WIN32)
   #  if !defined(BUILDING_NGHTTP2)
   #    undef ssize_t
   #  endif
   #endif

This does not require massive code changes, defines ssize_t properly and consistently for x86/x64 Windows platforms, and encapsulates ssize_t definition inside the library code offering NGHTTP2_SSIZE_T to one who uses this library in their own code.