C/C++ front-end: Revert scanner re-entrancy

There is no need for scanner re-entrancy, and using flex' re-entrancy
options fails the build on some macOS configurations. Partly reverts
1f240bc.

Author: tautschnig

src/ansi-c/ansi_c_language.cpp

@@ -82,13 +82,16 @@ bool ansi_c_languaget::parse(
   ansi_c_parser.cpp11=false; // it's not C++
   ansi_c_parser.mode=config.ansi_c.mode;
 
+  ansi_c_scanner_init(ansi_c_parser);
+
   bool result=ansi_c_parser.parse();
 
   if(!result)
   {
     ansi_c_parser.set_line_no(0);
     ansi_c_parser.set_file(path);
     ansi_c_parser.in=&i_preprocessed;
+    ansi_c_scanner_init(ansi_c_parser);
     result=ansi_c_parser.parse();
   }
 
@@ -202,6 +205,7 @@ bool ansi_c_languaget::to_expr(
   ansi_c_parser.cpp98 = false; // it's not C++
   ansi_c_parser.cpp11 = false; // it's not C++
   ansi_c_parser.mode = config.ansi_c.mode;
+  ansi_c_scanner_init(ansi_c_parser);
 
   bool result=ansi_c_parser.parse();
 

src/ansi-c/ansi_c_parser.cpp

@@ -10,23 +10,6 @@ Author: Daniel Kroening, [email protected]
 
 #include "c_storage_spec.h"
 
-int yyansi_clex_init_extra(ansi_c_parsert *, void **);
-int yyansi_clex_destroy(void *);
-int yyansi_cparse(ansi_c_parsert &, void *);
-void yyansi_cset_debug(int, void *);
-
-bool ansi_c_parsert::parse()
-{
-  void *scanner;
-  yyansi_clex_init_extra(this, &scanner);
-#ifdef ANSI_C_DEBUG
-  yyansi_cset_debug(1, scanner);
-#endif
-  bool parse_fail = yyansi_cparse(*this, scanner) != 0;
-  yyansi_clex_destroy(scanner);
-  return parse_fail;
-}
-
 ansi_c_id_classt ansi_c_parsert::lookup(
   const irep_idt &base_name,
   irep_idt &identifier, // output

src/ansi-c/ansi_c_parser.h

@@ -18,6 +18,9 @@ Author: Daniel Kroening, [email protected]
 #include "ansi_c_parse_tree.h"
 #include "ansi_c_scope.h"
 
+class ansi_c_parsert;
+int yyansi_cparse(ansi_c_parsert &);
+
 class ansi_c_parsert:public parsert
 {
 public:
@@ -41,7 +44,10 @@ class ansi_c_parsert:public parsert
     scopes.push_back(scopet());
   }
 
-  bool parse() override;
+  bool parse() override
+  {
+    return yyansi_cparse(*this) != 0;
+  }
 
   void clear() override
   {
@@ -169,4 +175,6 @@ class ansi_c_parsert:public parsert
   std::list<std::map<const irep_idt, bool>> pragma_cprover_stack;
 };
 
+void ansi_c_scanner_init(ansi_c_parsert &);
+
 #endif // CPROVER_ANSI_C_ANSI_C_PARSER_H

src/ansi-c/builtin_factory.cpp

@@ -58,6 +58,8 @@ static bool convert(
   ansi_c_parser.cpp11=false; // it's not C++
   ansi_c_parser.mode=config.ansi_c.mode;
 
+  ansi_c_scanner_init(ansi_c_parser);
+
   if(ansi_c_parser.parse())
     return true;