[cpp] buildmeta - added add_source function, which adds a path to a…

…n input file to the current build. note that this is a path relative to the cwd of the running psyc.

cpp/src/build.cpp

@@ -33,14 +33,19 @@ void set_output_name(const char* name)
 	cur_build_info->link_name = name;
 }
 
+void add_source(const char* name)
+{
+	cur_build_info->extra_input_files.push_back(name);
+}
+
 void install_functions(llvm::ExecutionEngine& exe)
 {
 	exe.addGlobalMapping("set_linkage_type", reinterpret_cast<std::uintptr_t>(&set_linkage_type));
 	exe.addGlobalMapping("set_build_type", reinterpret_cast<std::uintptr_t>(&set_build_type));
 	exe.addGlobalMapping("set_output_name", reinterpret_cast<std::uintptr_t>(&set_output_name));
+	exe.addGlobalMapping("add_source", reinterpret_cast<std::uintptr_t>(&add_source));
 }
 
-
 namespace build
 {
 
@@ -229,6 +234,24 @@ namespace build
 				.is_extern = true
 			}
 		});
+		ret.root.children.push_back(ast::node
+		{
+			.payload = ast::function_definition
+			{
+				.func_name = "add_source",
+				.params =
+				{
+					ast::variable_declaration
+					{
+						.var_name = "filename",
+						.type_name = "i8&",
+						.initialiser = ast::expression{.expr = ast::null_literal{}}
+					},
+				},
+				.ret_type = "u0",
+				.is_extern = true
+			}
+		});
 
 		// same with some globals.
 		for(int i = 0; i < (int)build::linkage_type::_count; i++)

cpp/src/lex.cpp

@@ -110,6 +110,7 @@ namespace lex
 		tokenise_state state;
 
 		std::ifstream fstr(psy_file);
+		diag::assert_that(fstr.good(), error_code::badargs, "could not open input file \"{}\"", psy_file.string());
 		// slurp the whole file into a string.
 		std::stringstream buffer;
 		buffer << fstr.rdbuf();

cpp/src/psyc_main.cpp

@@ -61,6 +61,11 @@ int main(int argc, char** argv)
 		std::size_t metacodegen = 0;
 		binfo = build::gather(args, &metalex, &metaparse, &metasemal, &metacodegen);
 		t.buildmeta = metalex + metaparse + metasemal + metacodegen;
+
+		for(std::filesystem::path extra : binfo.extra_input_files)
+		{
+			binfo.compiler_args.input_files.push_back(extra);
+		}
 	}
 	// remember: binfo might have extra input files than was specified in the command line.
 	// this is because build meta regions are allowed to add extra inputs.