Add definition pg_attribute_aligned() for MSVC

Visual Studio 2015+ has support for a macro to control the alignement of
structures as of __declspec(align(#)), and this commit adds a definition
of pg_attribute_aligned() based on that.  It happens that this was
already used in the implementation of atomics for MSVC.  Note that there
is still no definition fo pg_attribute_packed(), so this does not impact
itemptr.h.

Author: James Coleman
Discussion: https://postgr.es/m/CAAaqYe-HbtZvR3msoMtk+hYW2S0e0OapzMW8icSMYTMA+mN8Aw@mail.gmail.com

1 files changed, 2 insertions, 0 deletions

diff --git a/configure b/configure
index b04d9c8e80..4efed743a1 100755
--- a/configure
+++ b/configure
@@ -17462,6 +17462,8 @@ else
 /* This must match the corresponding code in c.h: */
 #if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
+#elif defined(_MSC_VER)
+#define pg_attribute_aligned(a) __declspec(align(a))
 #endif
 typedef __int128 int128a
 #if defined(pg_attribute_aligned)