Re-use C type conversion in C++ front-end

This avoids duplicating code and the need to update code in two places
to add new features.

Author: tautschnig

regression/ansi-c/always_inline5/test.desc

@@ -1,4 +1,4 @@
-CORE gcc-only broken-test-c++-front-end
+CORE gcc-only test-c++-front-end
 main.c
 
 ^EXIT=0$

regression/ansi-c/gcc_attributes3/test.desc

@@ -1,4 +1,4 @@
-CORE gcc-only broken-test-c++-front-end
+CORE gcc-only test-c++-front-end
 main.c
 
 ^EXIT=0$

regression/cpp/gcc_attributes1/main.cpp

@@ -0,0 +1,13 @@
+#ifdef __GNUC__
+
+const char *__attribute__((weak)) bar();
+#endif
+
+int main()
+{
+#ifdef __GNUC__
+  return bar() != 0;
+#else
+  return 0
+#endif
+}

regression/cpp/gcc_attributes1/test.desc

@@ -0,0 +1,8 @@
+CORE
+main.cpp
+
+^EXIT=0$
+^SIGNAL=0$
+--
+^warning: ignoring
+^CONVERSION ERROR$

src/ansi-c/ansi_c_convert_type.cpp

@@ -589,6 +589,13 @@ void ansi_c_convert_typet::write(typet &type)
     }
   }
 
+  build_type_with_subtype(type);
+  set_attributes(type);
+}
+
+/// Build a vector or complex type with \p type as subtype.
+void ansi_c_convert_typet::build_type_with_subtype(typet &type) const
+{
   if(vector_size.is_not_nil())
   {
     type_with_subtypet new_type(ID_frontend_vector, type);
@@ -604,7 +611,11 @@ void ansi_c_convert_typet::write(typet &type)
     new_type.add_source_location()=source_location;
     type.swap(new_type);
   }
+}
 
+/// Add qualifiers and GCC attributes onto \p type.
+void ansi_c_convert_typet::set_attributes(typet &type) const
+{
   if(gcc_attribute_mode.is_not_nil())
   {
     typet new_type=gcc_attribute_mode;

src/ansi-c/ansi_c_convert_type.h

@@ -51,8 +51,8 @@ class ansi_c_convert_typet:public messaget
   // qualifiers
   c_qualifierst c_qualifiers;
 
-  void read(const typet &type);
-  void write(typet &type);
+  virtual void read(const typet &type);
+  virtual void write(typet &type);
 
   source_locationt source_location;
 
@@ -64,7 +64,7 @@ class ansi_c_convert_typet:public messaget
   {
   }
 
-  void clear()
+  virtual void clear()
   {
     unsigned_cnt=signed_cnt=char_cnt=int_cnt=short_cnt=
     long_cnt=double_cnt=float_cnt=c_bool_cnt=proper_bool_cnt=complex_cnt=
@@ -90,7 +90,9 @@ class ansi_c_convert_typet:public messaget
   }
 
 protected:
-  void read_rec(const typet &type);
+  virtual void read_rec(const typet &type);
+  virtual void build_type_with_subtype(typet &type) const;
+  virtual void set_attributes(typet &type) const;
 };
 
 #endif // CPROVER_ANSI_C_ANSI_C_CONVERT_TYPE_H