[Ongoing] Rewrite frontend to use Flex/Bison

This is a merge of another experiment, so the changes are large:

- separated "modules" directory into frontend/backend
  - adjusted module names and moved files for this to happen
- removed modules lexer & parser
- removed all the unit tests (most were outdated)
- added Bison, flex, and C development tools to manifest.scm
- added lexer.l, a source file used by the flex utility with a functioning lexing implementation
- added parser.y, a source file used by the bison utility with a functioning parser implementation
- added node.c and node.h, which parser.y uses to construct an AST of a C source file (up to binary ops)
- added driver.c, a Guile-C interface that provides a module to scheme programs
- added a Makefile to make all of this
- added stuff to .gitignore

1 files changed, 88 insertions, 0 deletions

diff --git a/src/frontend/driver.c b/src/frontend/driver.c
new file mode 100644
index 0000000..52eb3f4
--- /dev/null
+++ b/src/frontend/driver.c
@@ -0,0 +1,88 @@
+#include "lexer.h"
+#include "parser.h"
+#include "node.h"
+#include <stdio.h>
+#include <libguile.h>
+
+/**
+ * @param node a tree of node structs representing a C source file.
+ * @return a scheme representation of node.
+ */
+SCM
+node_to_scm(Node *node) {
+  SCM ret = scm_list_1(scm_from_locale_symbol(node_types[node->type]));
+
+  SCM field_value = SCM_BOOL_F;
+  switch (node->type) {
+  case FUNC:
+    field_value = scm_from_locale_string(node->field.name);
+    break;
+  case EXPR:
+    field_value = scm_from_locale_symbol(node_ops[node->field.op]);
+    break;
+  case CONST:
+    field_value = scm_from_int32(node->field.val);
+    break;
+  default:
+    ;
+  }
+
+  if (scm_is_true(field_value))
+    ret = scm_append(scm_list_2(ret, scm_list_1(field_value)));
+
+  SCM child;
+  for (size_t i = 0; i < node->num_children; ++i) {
+    child = node_to_scm(node->children[i]);
+    ret = scm_append(scm_list_2(ret, scm_list_1(child)));
+  }
+
+  return ret;
+}
+
+/** \brief Parser driver for ull.
+ *         Given F, returns an AST of the program represented as a guile s-exp, or #f on a parse error.
+ *         if DO_PARSE is false, only performs lexing, returning #t on a success.
+ * @param f a preprocessed C file to parse.
+ * @param do_parse on false, do not perform the parsing stage.
+ * @return a SCM list representing the parse tree, or #t if do_parse is #f and lexing is successful, or #f otherwise.
+ */
+SCM
+file_to_ast_wrapper(SCM f, SCM do_parse)
+{
+  char *file = scm_to_locale_string(f);
+  Node *root = NULL;
+  SCM ret = SCM_BOOL_F;
+
+  yyin = fopen(file, "r");
+  if (yyin != NULL){
+    if (scm_is_true(do_parse)) {
+      if (yyparse(&root) == 0) {
+	ret = node_to_scm(root);
+	free_node(root);
+      }
+    } else {
+      ret = SCM_BOOL_T;
+      int token;
+      while ((token = yylex()) != 0) {
+	if (token == YYerror)
+	  ret = SCM_BOOL_F;
+      }
+    }
+  }
+
+  fclose(yyin);
+  free(file);
+  return ret;
+}
+
+void
+init_parser_driver()
+{
+  scm_c_define_gsubr("file->ast", 2, 0, 0, file_to_ast_wrapper);
+  scm_c_export("file->ast", NULL);
+}
+
+void
+scm_init_parser_driver_module() {
+  scm_c_define_module("frontend driver", init_parser_driver, NULL);
+}