fortran: C++ support for generating C prototypes

When generating C prototypes for Fortran procedures with the
-fc-prototypes and -fc-prototypes-external options, print a snippet
defining macros for complex types, and add C++ support by suppressing
mangling.

fortran/ChangeLog:

2019-05-12  Janne Blomqvist  <jb@gcc.gnu.org>

	* dump-parse-tree.c (get_c_type_name): Use macros for complex type
	names.
	* parse.c (gfc_parse_file): Define complex macros, add CPP support
	when printing C prototypes.

From-SVN: r271106

gcc/fortran/ChangeLog

+2019-05-12  Janne Blomqvist  <jb@gcc.gnu.org>
+
+	* dump-parse-tree.c (get_c_type_name): Use macros for complex type
+	names.
+	* parse.c (gfc_parse_file): Define complex macros, add CPP support
+	when printing C prototypes.
+
 2019-05-10  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/61968

gcc/fortran/dump-parse-tree.c

@@ -3143,11 +3143,11 @@ get_c_type_name (gfc_typespec *ts, gfc_array_spec *as, const char **pre,
 	  else if (strcmp (*type_name, "size_t") == 0)
 	    *type_name = "ssize_t";
 	  else if (strcmp (*type_name, "float_complex") == 0)
-	    *type_name = "float complex";
+	    *type_name = "__GFORTRAN_FLOAT_COMPLEX";
 	  else if (strcmp (*type_name, "double_complex") == 0)
-	    *type_name = "double complex";
+	    *type_name = "__GFORTRAN_DOUBLE_COMPLEX";
 	  else if (strcmp (*type_name, "long_double_complex") == 0)
-	    *type_name = "long double complex";
+	    *type_name = "__GFORTRAN_LONG_DOUBLE_COMPLEX";
 
 	  ret = T_OK;
 	}
@@ -3166,11 +3166,11 @@ get_c_type_name (gfc_typespec *ts, gfc_array_spec *as, const char **pre,
 		  else if (strcmp (*type_name, "size_t") == 0)
 		    *type_name = "ssize_t";
 		  else if (strcmp (*type_name, "float_complex") == 0)
-		    *type_name = "float complex";
+		    *type_name = "__GFORTRAN_FLOAT_COMPLEX";
 		  else if (strcmp (*type_name, "double_complex") == 0)
-		    *type_name = "double complex";
+		    *type_name = "__GFORTRAN_DOUBLE_COMPLEX";
 		  else if (strcmp (*type_name, "long_double_complex") == 0)
-		    *type_name = "long double complex";
+		    *type_name = "__GFORTRAN_LONG_DOUBLE_COMPLEX";
 
 		  ret = T_WARN;
 		  break;

gcc/fortran/parse.c

@@ -6331,6 +6331,24 @@ done:
       }
 
   /* Dump C prototypes.  */
+  if (flag_c_prototypes || flag_c_prototypes_external)
+    {
+      fprintf (stdout,
+	       _("#include <stddef.h>\n"
+		 "#ifdef __cplusplus\n"
+		 "#include <complex>\n"
+		 "#define __GFORTRAN_FLOAT_COMPLEX std::complex<float>\n"
+		 "#define __GFORTRAN_DOUBLE_COMPLEX std::complex<double>\n"
+		 "#define __GFORTRAN_LONG_DOUBLE_COMPLEX std::complex<long double>\n"
+		 "extern \"C\" {\n"
+		 "#else\n"
+		 "#define __GFORTRAN_FLOAT_COMPLEX float _Complex\n"
+		 "#define __GFORTRAN_DOUBLE_COMPLEX double _Complex\n"
+		 "#define __GFORTRAN_LONG_DOUBLE_COMPLEX long double _Complex\n"
+		 "#endif\n\n"));
+    }
+
+  /* First dump BIND(C) prototypes.  */
   if (flag_c_prototypes)
     {
       for (gfc_current_ns = gfc_global_ns_list; gfc_current_ns;
@@ -6342,6 +6360,10 @@ done:
   if (flag_c_prototypes_external)
     gfc_dump_external_c_prototypes (stdout);
 
+  if (flag_c_prototypes || flag_c_prototypes_external)
+    fprintf (stdout,
+	     _("\n#ifdef __cplusplus\n}\n#endif\n"));
+
   /* Do the translation.  */
   translate_all_program_units (gfc_global_ns_list);