Merge pull request #9724 from MisterDA/fix-domain-state

Fix #9714 "Compilation failure in domain_state.h"

Changes

@@ -260,6 +260,12 @@ Working version
   (Xavier Leroy, Sadiq Jaffer, Gabriel Scherer,
    review by Xavier Leroy and Jacques-Henri Jourdan)
 
+- #9714, #9724: Use the C++ alignas keyword when compiling in C++.
+  Fixes a bug with MSVC C++ 2015/2017. Add a terminator to the
+  `caml_domain_state` structure to better ensure that members are
+  correctly spaced.
+  (Antonin Décimo, review by David Allsopp and Xavier Leroy)
+
 OCaml 4.11
 ----------
 

runtime/caml/domain_state.h

@@ -33,6 +33,7 @@ typedef struct {
 #endif
 #include "domain_state.tbl"
 #undef DOMAIN_STATE
+    CAMLalign(8) char end_of_domain_state;
 } caml_domain_state;
 
 enum {
@@ -45,9 +46,8 @@ enum {
 /* Check that the structure was laid out without padding,
    since the runtime assumes this in computing offsets */
 CAML_STATIC_ASSERT(
-  sizeof(caml_domain_state) ==
-   (Domain_state_num_fields
-   ) * 8);
+    offsetof(caml_domain_state, end_of_domain_state) ==
+    Domain_state_num_fields * 8);
 
 CAMLextern caml_domain_state* Caml_state;
 #ifdef CAML_NAME_SPACE

runtime/caml/misc.h

@@ -96,6 +96,8 @@ CAMLdeprecated_typedef(addr, char *);
 /* we need to be able to compute the exact offset of each member. */
 #if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
 #define CAMLalign(n) _Alignas(n)
+#elif defined(__cplusplus) && (__cplusplus >= 201103L || _MSC_VER >= 1900)
+#define CAMLalign(n) alignas(n)
 #elif defined(SUPPORTS_ALIGNED_ATTRIBUTE)
 #define CAMLalign(n) __attribute__((aligned(n)))
 #elif _MSC_VER >= 1500