JSIL front-end: no need for parser reentrancy

Just make sure it isn't used in a reentrant manner.

Author: tautschnig

src/jsil/jsil_parser.cpp

@@ -11,6 +11,8 @@ Author: Michael Tautschnig, [email protected]
 
 #include "jsil_parser.h"
 
+int jsil_parsert::instance_count = 0;
+
 int yyjsillex_init_extra(jsil_parsert *, void **);
 int yyjsillex_destroy(void *);
 int yyjsilparse(jsil_parsert &, void *);

src/jsil/jsil_parser.h

@@ -22,6 +22,15 @@ class jsil_parsert:public parsert
   explicit jsil_parsert(message_handlert &message_handler)
     : parsert(message_handler)
   {
+    // simplistic check that we don't attempt to do reentrant parsing
+    PRECONDITION(++instance_count == 1);
+  }
+
+  jsil_parsert(const jsil_parsert &) = delete;
+
+  ~jsil_parsert() override
+  {
+    --instance_count;
   }
 
   jsil_parse_treet parse_tree;
@@ -39,6 +48,9 @@ class jsil_parsert:public parsert
 
   // internal state of the scanner
   std::string string_literal;
+
+protected:
+  static int instance_count;
 };
 
 #endif // CPROVER_JSIL_JSIL_PARSER_H

src/jsil/parser.y

@@ -5,7 +5,7 @@
 
 #include "jsil_parser.h"
 
-int yyjsillex(unsigned *, void *);
+int yyjsillex(void *);
 char *yyjsilget_text(void *);
 
 int yyjsilerror(
@@ -38,18 +38,8 @@ int yyjsilerror(
 // unreachable code
 #pragma warning(disable:4702)
 #endif
-
-// yynerrs may never be used. Will be fixed when bison > 3.8.2 is released (see
-// http://git.savannah.gnu.org/cgit/bison.git/commit/?id=a166d5450e3f47587b98f6005f9f5627dbe21a5b)
-#ifdef __clang__
-#  pragma clang diagnostic ignored "-Wunused-but-set-variable"
-#endif
 %}
 
-// Should be "%define api.pure full" instead of "%pure-parser", but macOS ships
-// bison 2.3, which doesn't yet support this. We have to invoke bison with
-// -Wno-deprecated on all platforms other than macOS.
-%pure-parser
 %parse-param {jsil_parsert &jsil_parser}
 %parse-param {void *scanner}
 %lex-param {void *scanner}