Issue #450 - Updated the runtime to avoid a race condition when creating new symbols

CHANGELOG.md

@@ -10,6 +10,7 @@ Features
 
 Bug Fixes
 
+- Updated the runtime to avoid a race condition when creating new symbols. Thanks to Skye Soss for the bug report and patch.
 - Prevent the compiler from inlining calls to primitives that open ports, avoiding a range of issues such as an open file operation being inlined across multiple places in the intermediate code.
 - Arthur Maciel updated `current-jiffy` to use `clock_gettime`.
 

runtime.c

@@ -454,9 +454,16 @@ static object find_symbol_by_name(const char *name)
 object add_symbol(symbol_type * psym)
 {
   pthread_mutex_lock(&symbol_table_lock);       // Only 1 "writer" allowed
-  set_insert(&symbol_table, psym);
+  bool inserted = set_insert(&symbol_table, psym);
   pthread_mutex_unlock(&symbol_table_lock);
-  return psym;
+  if (!inserted) {
+    object sym = find_symbol_by_name(psym->desc);
+    free((char *)(psym->desc));
+    free(psym);
+    return sym;
+  } else {
+    return psym;
+  }
 }
 
 static object add_symbol_by_name(const char *name)

scheme/cyclone/cgen.sld

@@ -2162,12 +2162,6 @@
       *globals*)
     (emit "")
 
-    ;; Initialize symbol table
-    (for-each
-        (lambda (sym)
-            (emit* "  add_symbol(quote_" (mangle sym) ");"))
-        *symbols*)
-
     ;; Initialize globals
     (let* ((prefix "  ")
            (emit-global