MPR#7638: in the Windows Mingw64 port, multithreaded programs compiled to bytecode can crash when raising an exception from C codeMPR7638

This is a known problem with setjmp/longjmp in Mingw64.  This commit works around the issue by using GCC's __builtin_setjmp/__builtin_longjmp functions instead.

2 files changed, 12 insertions, 0 deletions

diff --git a/Changes b/Changes
index 486cbf262e..42f6bdf670 100644
--- a/Changes
+++ b/Changes
@@ -564,6 +564,11 @@ Release branch for 4.06:
   under ocamldebug calls Pervasives.flush_all
   (Xavier Leroy, report by Paul Steckler, review by Gabriel Scherer)
 
+- MPR#7638: in the Windows Mingw64 port, multithreaded programs compiled
+  to bytecode could crash when raising an exception from C code.
+  This looks like a Mingw64 issue, which we work around with GCC builtins.
+  (Xavier Leroy)
+
 - GPR#1155: Fix a race condition with WAIT_NOHANG on Windows
   (Jérémie Dimino and David Allsopp)
 
diff --git a/byterun/caml/fail.h b/byterun/caml/fail.h
index 3ae82b1e96..54907e4259 100644
--- a/byterun/caml/fail.h
+++ b/byterun/caml/fail.h
@@ -44,6 +44,13 @@
 struct longjmp_buffer {
   sigjmp_buf buf;
 };
+#elif defined(__MINGW64__) && defined(__GNUC__) && __GNUC__ >= 4
+/* MPR#7638: issues with setjmp/longjmp in Mingw64, use GCC builtins instead */
+struct longjmp_buffer {
+  intptr_t buf[5];
+};
+#define sigsetjmp(buf,save) __builtin_setjmp(buf)
+#define siglongjmp(buf,val) __builtin_longjmp(buf,val)
 #else
 struct longjmp_buffer {
   jmp_buf buf;