Re-enable FTL JIT on macOS

Fixes #820

CHANGELOG.md

@@ -7,6 +7,9 @@ All notable changes to this project will be documented in this file. This change
 - Add -keep-gcl option to the clean script
 - Ignore `*.swp` files
 
+### Changed
+- Re-enable FTL JIT on macOS ([#820](https://github.com/planck-repl/planck/issues/820))
+
 ### Fixed
 - Switch `strncpy` to `memcpy` to avoid GCC warning
 - Backslash return return should produce "\n" ([661](https://github.com/planck-repl/planck/issues/661))

planck-c/main.c

@@ -9,6 +9,10 @@
 #include <signal.h>
 #include <sys/stat.h>
 
+#ifdef __APPLE__
+#include <mach-o/dyld.h>
+#endif
+
 #include "bundle.h"
 #include "engine.h"
 #include "globals.h"
@@ -315,10 +319,18 @@ bool should_ignore_arg(const char *opt) {
 
 void control_FTL_JIT() {
 
-    // Recent versions of JavaScriptCore are crashing in FTL JIT.
-    // Disable FTL JIT if JSC_useFTLJIT env var not set.
+    // Older versions of JavaScriptCore were crashing in FTL JIT.
+    // Disable FTL JIT if older version on macOS or on Unix and
+    // JSC_useFTLJIT env var not set.
+
+#ifdef __APPLE__
+    int32_t jsc_version = NSVersionOfLinkTimeLibrary("JavaScriptCore");
+    bool check_env = (jsc_version < 0x25f0128);
+#else
+    bool check_env = true;
+#endif
 
-    if (getenv("JSC_useFTLJIT") == NULL) {
+    if (check_env && getenv("JSC_useFTLJIT") == NULL) {
         putenv("JSC_useFTLJIT=false");
     }