Merge pull request #10797 from dra27/fix-volatile

Fix compilation of systhreads on Visual Studio 2019 and 2022

Changes

@@ -384,6 +384,11 @@ OCaml 4.14.0
   (Sébastien Hinderer, review by David Allsopp, Daniel Bünzli, Xavier Leroy
   and Gabriel Scherer)
 
+- #10797: Compile with -d2VolatileMetadata- on supporting versions of Visual
+  Studio. This suppresses the addition of .voltbl sections and eliminates
+  linking errors in systhreads.
+  (David Allsopp, review by Jonah Beckford and Sébastien Hinderer)
+
 ### Bug fixes:
 
 - #9214, #10709: Wrong unmarshaling of function pointers in debugger mode.

aclocal.m4

@@ -129,6 +129,19 @@ AC_DEFUN([OCAML_CC_HAS_DEBUG_PREFIX_MAP], [
   CFLAGS="$saved_CFLAGS"
 ])
 
+AC_DEFUN([OCAML_CL_HAS_VOLATILE_METADATA], [
+  AC_MSG_CHECKING([whether the C compiler supports -d2VolatileMetadata-])
+  saved_CFLAGS="$CFLAGS"
+  CFLAGS="-d2VolatileMetadata- $CFLAGS"
+  AC_COMPILE_IFELSE(
+    [AC_LANG_SOURCE([int main() { return 0; }])],
+    [cl_has_volatile_metadata=true
+    AC_MSG_RESULT([yes])],
+    [cl_has_volatile_metadata=false
+    AC_MSG_RESULT([no])])
+  CFLAGS="$saved_CFLAGS"
+])
+
 # Save C compiler related variables
 AC_DEFUN([OCAML_CC_SAVE_VARIABLES], [
   saved_CC="$CC"

configure.ac

@@ -676,6 +676,9 @@ AS_CASE([$host],
       [common_cflags="-nologo -O2 -Gy- -MD $cc_warnings"
       common_cppflags="-D_CRT_SECURE_NO_DEPRECATE"
       internal_cppflags='-DUNICODE -D_UNICODE'
+      OCAML_CL_HAS_VOLATILE_METADATA
+      AS_IF([test "x$cl_has_volatile_metadata" = "xtrue"],
+            [internal_cflags='-d2VolatileMetadata-'])
       internal_cppflags="$internal_cppflags -DWINDOWS_UNICODE="
       internal_cppflags="${internal_cppflags}\$(WINDOWS_UNICODE)"],
     [xlc-*],