Fix linker problems when compiling as C++.

When compiling compat-5.3.c as C++, the Lua symbols may still have
C-linkage. Reference those symbols as `extern "C"` by default and add an
option for normal (C++) linkage.

2 files changed, 6 insertions, 2 deletions

diff --git a/c-api/compat-5.3.c b/c-api/compat-5.3.c
index 8385bba..34b8001 100644
--- a/c-api/compat-5.3.c
+++ b/c-api/compat-5.3.c
@@ -3,8 +3,6 @@
 #include <string.h>
 #include <ctype.h>
 #include <errno.h>
-#include <lua.h>
-#include <lauxlib.h>
 #include "compat-5.3.h"
 
 /* don't compile it again if it already is included via compat53.h */
diff --git a/c-api/compat-5.3.h b/c-api/compat-5.3.h
index e3bbb11..3f1cacc 100644
--- a/c-api/compat-5.3.h
+++ b/c-api/compat-5.3.h
@@ -4,8 +4,14 @@
 #include <stddef.h>
 #include <limits.h>
 #include <string.h>
+#if defined( __cplusplus ) && !defined( COMPAT53_LUA_CPP )
+extern "C" {
+#endif
 #include <lua.h>
 #include <lauxlib.h>
+#if defined( __cplusplus ) && !defined( COMPAT53_LUA_CPP )
+}
+#endif
 
 
 #if defined(COMPAT53_PREFIX)