Fixed a include build issue for Cygwin in non-POSIX (Win32) mode. (#1917, #1319, #276)

CHANGELOG.txt

@@ -40,6 +40,7 @@ Other Changes:
  - Window: Allow menu windows from ignoring the style.WindowMinSize values so short menus are not padded. (#1909)
  - Misc: Added ImGuiMouseCursor_Hand cursor enum + corresponding software cursor. (#1913, 1914) [@aiekick, @ocornut] 
  - Misc: Tweaked software mouse cursor offset to match the offset of the corresponding Windows 10 cursors.
+ - Fixed a include build issue for Cygwin in non-POSIX (Win32) mode. (#1917, #1319, #276)
  - Examples: Win32, Glfw, SDL: Added support for the ImGuiMouseCursor_Hand cursor.
 
 -----------------------------------------------------------------------

imgui_draw.cpp

@@ -19,13 +19,13 @@
 
 #include <stdio.h>      // vsnprintf, sscanf, printf
 #if !defined(alloca)
-#ifdef _WIN32
+#if defined(__GLIBC__) || defined(__sun) || defined(__CYGWIN__)
+#include <alloca.h>     // alloca (glibc uses <alloca.h>. Note that Cygwin may have _WIN32 defined, so the order matters here)
+#elif defined(_WIN32)
 #include <malloc.h>     // alloca
 #if !defined(alloca)
 #define alloca _alloca  // for clang with MS Codegen
 #endif
-#elif defined(__GLIBC__) || defined(__sun)
-#include <alloca.h>     // alloca
 #else
 #include <stdlib.h>     // alloca
 #endif