From 6a87bb2d56d60bba6451b860a36667a164bf446c Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Mon, 9 Feb 2026 21:21:49 -0500
Subject: [PATCH] Add support for multiple starting rules - close #38

---
 assets/parser.c.erb            | 55 ++++++++++++++++++++++++++++------
 assets/parser.d.erb            | 45 ++++++++++++++++++++++------
 assets/parser.h.erb            | 22 +++++++++++---
 doc/user_guide.md              | 54 +++++++++++++++++++++++++++++++++
 lib/propane/generator.rb       | 17 ++++++-----
 lib/propane/grammar.rb         | 14 +++++----
 lib/propane/parser.rb          | 15 ++++++++--
 spec/propane_spec.rb           | 41 +++++++++++++++++++++++++
 spec/test_starting_rules.c     | 27 +++++++++++++++++
 spec/test_starting_rules.d     | 29 ++++++++++++++++++
 spec/test_starting_rules_ast.c | 37 +++++++++++++++++++++++
 spec/test_starting_rules_ast.d | 36 ++++++++++++++++++++++
 spec/testutils.c               | 18 +++++++++++
 spec/testutils.h               | 10 +++++++
 14 files changed, 383 insertions(+), 37 deletions(-)
 create mode 100644 spec/test_starting_rules.c
 create mode 100644 spec/test_starting_rules.d
 create mode 100644 spec/test_starting_rules_ast.c
 create mode 100644 spec/test_starting_rules_ast.d

diff --git a/assets/parser.c.erb b/assets/parser.c.erb
index 45002b8..f70532a 100644
--- a/assets/parser.c.erb
+++ b/assets/parser.c.erb
@@ -924,6 +924,8 @@ static size_t check_reduce(size_t state_id, <%= @grammar.prefix %>token_t token)
  *
  * @param context
  *   Lexer/parser context structure.
+ * @start_state_id
+ *   ID of the state in which to start.
  *
  * @retval P_SUCCESS
  *   The parser successfully matched the input text. The parse result value
@@ -936,7 +938,7 @@ static size_t check_reduce(size_t state_id, <%= @grammar.prefix %>token_t token)
  * @reval P_UNEXPECTED_INPUT
  *   Input text does not match any lexer pattern.
  */
-size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
+static size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start_state_id)
 {
     <%= @grammar.prefix %>token_info_t token_info;
     <%= @grammar.prefix %>token_t token = INVALID_TOKEN_ID;
@@ -949,6 +951,7 @@ size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
 <% end %>
     state_values_stack_init(&statevalues);
     state_values_stack_push(&statevalues);
+    state_values_stack_index(&statevalues, -1)->state_id = start_state_id;
     size_t result;
     for (;;)
     {
@@ -974,7 +977,7 @@ size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
             {
                 /* Successful parse. */
 <% if @grammar.ast %>
-                context->parse_result = (<%= @grammar.ast_prefix %><%= @grammar.start_rule %><%= @grammar.ast_suffix %> *)state_values_stack_index(&statevalues, -1)->ast_node;
+                context->parse_result = state_values_stack_index(&statevalues, -1)->ast_node;
 <% else %>
                 context->parse_result = state_values_stack_index(&statevalues, -1)->pvalue;
 <% end %>
@@ -1101,6 +1104,19 @@ size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
     return result;
 }
 
+size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
+{
+    return parse_from(context, 0u);
+}
+
+<% @grammar.start_rules.each_with_index do |start_rule, i| %>
+
+size_t <%= @grammar.prefix %>parse_<%= start_rule %>(<%= @grammar.prefix %>context_t * context)
+{
+    return parse_from(context, <%= i %>u);
+}
+<% end %>
+
 /**
  * Get the parse result value.
  *
@@ -1110,17 +1126,28 @@ size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
  * @return Parse result value.
  */
 <% if @grammar.ast %>
-<%= @grammar.ast_prefix %><%= @grammar.start_rule %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context)
+<%= @grammar.ast_prefix %><%= @grammar.start_rules[0] %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context)
+{
+    return (<%= @grammar.ast_prefix %><%= @grammar.start_rules[0] %><%= @grammar.ast_suffix %> *) context->parse_result;
+}
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+<%= @grammar.ast_prefix %><%= start_rule %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result_<%= start_rule %>(<%= @grammar.prefix %>context_t * context)
+{
+    return (<%= @grammar.ast_prefix %><%= start_rule %><%= @grammar.ast_suffix %> *) context->parse_result;
+}
+<%   end %>
 <% else %>
 <%= start_rule_type[1] %> <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context)
-<% end %>
 {
-<% if @grammar.ast %>
-    return context->parse_result;
-<% else %>
     return context->parse_result.v_<%= start_rule_type[0] %>;
-<% end %>
 }
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+<%= start_rule_type(i)[1] %> <%= @grammar.prefix %>result_<%= start_rule %>(<%= @grammar.prefix %>context_t * context)
+{
+    return context->parse_result.v_<%= start_rule_type(i)[0] %>;
+}
+<%   end %>
+<% end %>
 
 /**
  * Get the current text input position.
@@ -1184,8 +1211,18 @@ static void free_ast_node(ASTNode * node)
 /**
  * Free all AST node memory.
  */
-void <%= @grammar.prefix %>free_ast(<%= @grammar.ast_prefix %><%= @grammar.start_rule %><%= @grammar.ast_suffix %> * ast)
+void <%= @grammar.prefix %>free_ast(<%= @grammar.ast_prefix %><%= @grammar.start_rules[0] %><%= @grammar.ast_suffix %> * ast)
 {
     free_ast_node((ASTNode *)ast);
 }
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+
+/**
+ * Free all AST node memory.
+ */
+void <%= @grammar.prefix %>free_ast_<%= start_rule %>(<%= @grammar.ast_prefix %><%= start_rule %><%= @grammar.ast_suffix %> * ast)
+{
+    free_ast_node((ASTNode *)ast);
+}
+<%   end %>
 <% end %>
diff --git a/assets/parser.d.erb b/assets/parser.d.erb
index a643652..99eac22 100644
--- a/assets/parser.d.erb
+++ b/assets/parser.d.erb
@@ -173,7 +173,7 @@ public struct <%= @grammar.prefix %>context_t
 
     /** Parse result value. */
 <% if @grammar.ast %>
-    <%= @grammar.ast_prefix %><%= @grammar.start_rule %><%= @grammar.ast_suffix %> * parse_result;
+    void * parse_result;
 <% else %>
     <%= @grammar.prefix %>value_t parse_result;
 <% end %>
@@ -985,6 +985,8 @@ private size_t check_reduce(size_t state_id, <%= @grammar.prefix %>token_t token
  *
  * @param context
  *   Lexer/parser context structure.
+ * @start_state_id
+ *   ID of the state in which to start.
  *
  * @retval P_SUCCESS
  *   The parser successfully matched the input text. The parse result value
@@ -997,11 +999,12 @@ private size_t check_reduce(size_t state_id, <%= @grammar.prefix %>token_t token
  * @reval P_UNEXPECTED_INPUT
  *   Input text does not match any lexer pattern.
  */
-public size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
+private size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start_state_id)
 {
     <%= @grammar.prefix %>token_info_t token_info;
     <%= @grammar.prefix %>token_t token = INVALID_TOKEN_ID;
     state_value_t[] statevalues = new state_value_t[](1);
+    statevalues[0].state_id = start_state_id;
     size_t reduced_rule_set = INVALID_ID;
 <% if @grammar.ast %>
     void * reduced_parser_node;
@@ -1031,7 +1034,7 @@ public size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * cont
             {
                 /* Successful parse. */
 <% if @grammar.ast %>
-                context.parse_result = cast(<%= @grammar.ast_prefix %><%= @grammar.start_rule %><%= @grammar.ast_suffix %> *)statevalues[$-1].ast_node;
+                context.parse_result = statevalues[$-1].ast_node;
 <% else %>
                 context.parse_result = statevalues[$-1].pvalue;
 <% end %>
@@ -1147,6 +1150,19 @@ public size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * cont
     }
 }
 
+public size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
+{
+    return parse_from(context, 0u);
+}
+
+<% @grammar.start_rules.each_with_index do |start_rule, i| %>
+
+public size_t <%= @grammar.prefix %>parse_<%= start_rule %>(<%= @grammar.prefix %>context_t * context)
+{
+    return parse_from(context, <%= i %>u);
+}
+<% end %>
+
 /**
  * Get the parse result value.
  *
@@ -1156,17 +1172,28 @@ public size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * cont
  * @return Parse result value.
  */
 <% if @grammar.ast %>
-public <%= @grammar.ast_prefix %><%= @grammar.start_rule %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context)
+public <%= @grammar.ast_prefix %><%= @grammar.start_rules[0] %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context)
+{
+    return cast(<%= @grammar.ast_prefix %><%= @grammar.start_rules[0] %><%= @grammar.ast_suffix %> *)context.parse_result;
+}
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+public <%= @grammar.ast_prefix %><%= start_rule %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result_<%= start_rule %>(<%= @grammar.prefix %>context_t * context)
+{
+    return cast(<%= @grammar.ast_prefix %><%= start_rule %><%= @grammar.ast_suffix %> *)context.parse_result;
+}
+<%   end %>
 <% else %>
 public <%= start_rule_type[1] %> <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context)
-<% end %>
 {
-<% if @grammar.ast %>
-    return context.parse_result;
-<% else %>
     return context.parse_result.v_<%= start_rule_type[0] %>;
-<% end %>
 }
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+public <%= start_rule_type(i)[1] %> <%= @grammar.prefix %>result_<%= start_rule %>(<%= @grammar.prefix %>context_t * context)
+{
+    return context.parse_result.v_<%= start_rule_type(i)[0] %>;
+}
+<%   end %>
+<% end %>
 
 /**
  * Get the current text input position.
diff --git a/assets/parser.h.erb b/assets/parser.h.erb
index 86a8b1e..2b8fc43 100644
--- a/assets/parser.h.erb
+++ b/assets/parser.h.erb
@@ -162,7 +162,7 @@ typedef struct
 
     /** Parse result value. */
 <% if @grammar.ast %>
-    <%= @grammar.ast_prefix %><%= @grammar.start_rule %><%= @grammar.ast_suffix %> * parse_result;
+    void * parse_result;
 <% else %>
     <%= @grammar.prefix %>value_t parse_result;
 <% end %>
@@ -189,13 +189,27 @@ size_t <%= @grammar.prefix %>decode_code_point(uint8_t const * input, size_t inp
 size_t <%= @grammar.prefix %>lex(<%= @grammar.prefix %>context_t * context, <%= @grammar.prefix %>token_info_t * out_token_info);
 
 size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context);
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+size_t <%= @grammar.prefix %>parse_<%= start_rule %>(<%= @grammar.prefix %>context_t * context);
+<%   end %>
 
 <% if @grammar.ast %>
-<%= @grammar.ast_prefix %><%= @grammar.start_rule %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context);
-
-void <%= @grammar.prefix %>free_ast(<%= @grammar.ast_prefix %><%= @grammar.start_rule %><%= @grammar.ast_suffix %> * ast);
+<%= @grammar.ast_prefix %><%= @grammar.start_rules[0] %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context);
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+<%= @grammar.ast_prefix %><%= start_rule %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result_<%= start_rule %>(<%= @grammar.prefix %>context_t * context);
+<%   end %>
 <% else %>
 <%= start_rule_type[1] %> <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context);
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+<%= start_rule_type(i)[1] %> <%= @grammar.prefix %>result_<%= start_rule %>(<%= @grammar.prefix %>context_t * context);
+<%   end %>
+<% end %>
+
+<% if @grammar.ast %>
+void <%= @grammar.prefix %>free_ast(<%= @grammar.ast_prefix %><%= @grammar.start_rules[0] %><%= @grammar.ast_suffix %> * ast);
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+void <%= @grammar.prefix %>free_ast_<%= start_rule %>(<%= @grammar.ast_prefix %><%= start_rule %><%= @grammar.ast_suffix %> * ast);
+<%   end %>
 <% end %>
 
 <%= @grammar.prefix %>position_t <%= @grammar.prefix %>position(<%= @grammar.prefix %>context_t * context);
diff --git a/doc/user_guide.md b/doc/user_guide.md
index 0e4cb45..adb4101 100644
--- a/doc/user_guide.md
+++ b/doc/user_guide.md
@@ -738,6 +738,22 @@ Example:
 start MyStartRule;
 ```
 
+Multiple start rules can be specified, either with multiple `start` statements
+or one `start` statement listing multiple start rules.
+Example:
+
+```
+start Module ModuleItem Statement Expression;
+```
+
+When multiple start rules are specified, multiple `p_parse_*()` functions,
+`p_result_*()`, and `p_free_ast_*()` functions (in AST mode) are generated.
+A default `p_parse()`, `p_result()`, `p_free_ast()` are generated corresponding
+to the first start rule.
+Additionally, each start rule causes the generation of another version of each
+of these functions, for example `p_parse_Statement()`, `p_result_Statement()`,
+and `p_free_ast_Statement()`.
+
 ##> Specifying the parser module name - the `module` statement
 
 The `module` statement can be used to specify the module name for a generated
@@ -1018,6 +1034,16 @@ p_context_init(&context, input, input_length);
 size_t result = p_parse(&context);
 ```
 
+When multiple start rules are specified, a separate parse function is generated
+for each which starts parsing at the given rule.
+For example, if `Statement` is specified as a start rule:
+
+```
+size_t result = p_parse_Statement(&context);
+```
+
+In this case, the parser will start parsing with the `Statement` rule.
+
 ### `p_position_valid`
 
 The `p_position_valid()` function is only generated for C targets.
@@ -1056,6 +1082,23 @@ if (p_parse(&context) == P_SUCCESS)
 If AST generation mode is active, then the `p_result()` function returns a
 `Start *` pointing to the `Start` AST structure.
 
+When multiple start rules are specified, a separate result function is generated
+for each which returns the parse result for the corresponding rule.
+For example, if `Statement` is specified as a start rule:
+
+```
+p_context_t context;
+p_context_init(&context, input, input_length);
+size_t result = p_parse(&context);
+if (p_parse_Statement(&context) == P_SUCCESS)
+{
+    result = p_result_Statement(&context);
+}
+```
+
+In this case, the parser will start parsing with the `Statement` rule and the
+parse result from the `Statement` rule will be returned.
+
 ### `p_position`
 
 The `p_position()` function can be used to retrieve the parser position where
@@ -1142,6 +1185,17 @@ If specified, the `free_token_node` function will be called during the
 `p_free_ast()` process to allow user code to free any memory associated with
 a token node's `pvalue`.
 
+When multiple start rules are specified, a separate `p_free_ast` function is
+generated for each which frees the AST resulting from parsing the given rule.
+For example, if `Statement` is specified as a start rule:
+
+```
+p_free_ast_Statement(statement_ast);
+```
+
+In this case, Propane will free a `Statement` AST structure returned by the
+`p_parse_Statement(&context)` function.
+
 ##> Data
 
 ### `p_token_names`
diff --git a/lib/propane/generator.rb b/lib/propane/generator.rb
index e54e8dd..2fb3b26 100644
--- a/lib/propane/generator.rb
+++ b/lib/propane/generator.rb
@@ -71,12 +71,15 @@ class Propane
         end
         tokens_by_name[token.name] = token
       end
-      # Check for user start rule.
-      unless @grammar.rules.find {|rule| rule.name == @grammar.start_rule}
-        raise Error.new("Start rule `#{@grammar.start_rule}` not found")
+      # Create real start rule(s).
+      real_start_rules = @grammar.start_rules.map do |start_rule|
+        unless @grammar.rules.find {|rule| rule.name == start_rule}
+          raise Error.new("Start rule `#{start_rule}` not found")
+        end
+        Rule.new("$#{start_rule}", [start_rule, "$EOF"], nil, nil, nil)
       end
-      # Add "real" start rule.
-      @grammar.rules.unshift(Rule.new("$Start", [@grammar.start_rule, "$EOF"], nil, nil, nil))
+      # Add real start rules before user-given rules.
+      @grammar.rules = real_start_rules + @grammar.rules
       # Generate and add rules for optional components.
       generate_optional_component_rules!(tokens_by_name)
       # Build rule sets.
@@ -332,9 +335,9 @@ class Propane
     #
     # @return [Array<String>]
     #   Start rule parser value type name and type string.
-    def start_rule_type
+    def start_rule_type(start_rule_index = 0)
       start_rule = @grammar.rules.find do |rule|
-        rule.name == @grammar.start_rule
+        rule.name == @grammar.start_rules[start_rule_index]
       end
       [start_rule.ptypename, @grammar.ptypes[start_rule.ptypename]]
     end
diff --git a/lib/propane/grammar.rb b/lib/propane/grammar.rb
index f12c330..8572c28 100644
--- a/lib/propane/grammar.rb
+++ b/lib/propane/grammar.rb
@@ -11,8 +11,8 @@ class Propane
     attr_reader :free_token_node
     attr_reader :modulename
     attr_reader :patterns
-    attr_reader :rules
-    attr_reader :start_rule
+    attr_accessor :rules
+    attr_reader :start_rules
     attr_reader :tokens
     attr_reader :code_blocks
     attr_reader :ptypes
@@ -20,7 +20,7 @@ class Propane
 
     def initialize(input)
       @patterns = []
-      @start_rule = "Start"
+      @start_rules = []
       @tokens = []
       @rules = []
       @code_blocks = {}
@@ -35,6 +35,7 @@ class Propane
       @ast_suffix = ""
       @free_token_node = nil
       parse_grammar!
+      @start_rules << "Start" if @start_rules.empty?
     end
 
     def ptype
@@ -241,8 +242,11 @@ class Propane
     end
 
     def parse_start_statement!
-      if md = consume!(/start\s+(\w+)\s*;/)
-        @start_rule = md[1]
+      if md = consume!(/start\s+([\w\s]*);/)
+        start_rules = md[1].split(/\s+/).map(&:strip)
+        start_rules.each do |start_rule|
+          @start_rules << start_rule unless @start_rules.include?(start_rule)
+        end
       end
     end
 
diff --git a/lib/propane/parser.rb b/lib/propane/parser.rb
index c980142..56432b9 100644
--- a/lib/propane/parser.rb
+++ b/lib/propane/parser.rb
@@ -16,11 +16,20 @@ class Propane
       @warnings = Set.new
       @errors = Set.new
       @options = options
-      start_item = Item.new(grammar.rules.first, 0)
-      eval_item_sets = Set[ItemSet.new([start_item])]
+      start_items = grammar.rules[0...grammar.start_rules.length].map do |start_rule|
+        Item.new(start_rule, 0)
+      end
+      start_item_sets = start_items.map {|item| ItemSet.new([item])}
+      eval_item_sets = Set[*start_item_sets]
 
       while eval_item_sets.size > 0
-        item_set = eval_item_sets.first
+        item_set =
+          if start_item_sets.size > 0
+            # Ensure we evaluate start_item_sets first in order
+            start_item_sets.slice!(0)
+          else
+            eval_item_sets.first
+          end
         eval_item_sets.delete(item_set)
         unless @item_sets_set.include?(item_set)
           item_set.id = @item_sets.size
diff --git a/spec/propane_spec.rb b/spec/propane_spec.rb
index 4e83d7a..3a100ff 100644
--- a/spec/propane_spec.rb
+++ b/spec/propane_spec.rb
@@ -1440,6 +1440,47 @@ EOF
         expect(results.status).to eq 0
       end
 
+      it "allows multiple starting rules" do
+    write_grammar <<EOF
+ptype int;
+token a << $$ = 1; >>
+token b << $$ = 2; >>
+token c << $$ = 3; >>
+Start -> a b R;
+Start -> Bs:bs << $$ = $1; >>
+R -> c:c << $$ = $1; >>
+Bs -> << $$ = 0; >>
+Bs -> b:b Bs:bs << $$ = $1 + $2; >>
+start Start R Bs;
+EOF
+        run_propane(language: language)
+        compile("spec/test_starting_rules.#{language}", language: language)
+        results = run_test(language: language)
+        expect(results.stderr).to eq ""
+        expect(results.status).to eq 0
+      end
+
+      it "allows multiple starting rules in AST mode" do
+    write_grammar <<EOF
+ast;
+ptype int;
+token a << $$ = 1; >>
+token b << $$ = 2; >>
+token c << $$ = 3; >>
+Start -> a b R;
+Start -> Bs:bs;
+R -> c:c;
+Bs -> ;
+Bs -> b:b Bs:bs;
+start Start R Bs;
+EOF
+        run_propane(language: language)
+        compile("spec/test_starting_rules_ast.#{language}", language: language)
+        results = run_test(language: language)
+        expect(results.stderr).to eq ""
+        expect(results.status).to eq 0
+      end
+
       if %w[c cpp].include?(language)
         it "allows a user function to free token node memory in AST mode" do
     write_grammar <<EOF
diff --git a/spec/test_starting_rules.c b/spec/test_starting_rules.c
new file mode 100644
index 0000000..0d23c01
--- /dev/null
+++ b/spec/test_starting_rules.c
@@ -0,0 +1,27 @@
+#include "testparser.h"
+#include <assert.h>
+#include <string.h>
+#include "testutils.h"
+
+int main()
+{
+    char const * input = "bbbb";
+    p_context_t context;
+    p_context_init(&context, (uint8_t const *)input, strlen(input));
+    assert(p_parse(&context) == P_SUCCESS);
+    int result = p_result(&context);
+    assert_eq(8, result);
+
+    p_context_init(&context, (uint8_t const *)input, strlen(input));
+    assert(p_parse_Bs(&context) == P_SUCCESS);
+    result = p_result_Bs(&context);
+    assert_eq(8, result);
+
+    input = "c";
+    p_context_init(&context, (uint8_t const *)input, strlen(input));
+    assert(p_parse_R(&context) == P_SUCCESS);
+    result = p_result_R(&context);
+    assert_eq(3, result);
+
+    return 0;
+}
diff --git a/spec/test_starting_rules.d b/spec/test_starting_rules.d
new file mode 100644
index 0000000..bb32022
--- /dev/null
+++ b/spec/test_starting_rules.d
@@ -0,0 +1,29 @@
+import testparser;
+import std.stdio;
+import testutils;
+
+int main()
+{
+    return 0;
+}
+
+unittest
+{
+    string input = "bbbb";
+    p_context_t context;
+    p_context_init(&context, input);
+    assert(p_parse(&context) == P_SUCCESS);
+    int result = p_result(&context);
+    assert(result == 8);
+
+    p_context_init(&context, input);
+    assert(p_parse_Bs(&context) == P_SUCCESS);
+    result = p_result_Bs(&context);
+    assert(result == 8);
+
+    input = "c";
+    p_context_init(&context, input);
+    assert(p_parse_R(&context) == P_SUCCESS);
+    result = p_result_R(&context);
+    assert(result == 3);
+}
diff --git a/spec/test_starting_rules_ast.c b/spec/test_starting_rules_ast.c
new file mode 100644
index 0000000..8a2ca00
--- /dev/null
+++ b/spec/test_starting_rules_ast.c
@@ -0,0 +1,37 @@
+#include "testparser.h"
+#include <assert.h>
+#include <string.h>
+#include "testutils.h"
+
+int main()
+{
+    char const * input = "bbbb";
+    p_context_t context;
+    p_context_init(&context, (uint8_t const *)input, strlen(input));
+    assert(p_parse(&context) == P_SUCCESS);
+    Start * start = p_result(&context);
+    assert_not_null(start->bs);
+    assert_not_null(start->bs->b);
+    assert_not_null(start->bs->bs->b);
+    assert_not_null(start->bs->bs->bs->b);
+    assert_not_null(start->bs->bs->bs->bs->b);
+    p_free_ast(start);
+
+    p_context_init(&context, (uint8_t const *)input, strlen(input));
+    assert(p_parse_Bs(&context) == P_SUCCESS);
+    Bs * bs = p_result_Bs(&context);
+    assert_not_null(bs->b);
+    assert_not_null(bs->bs->b);
+    assert_not_null(bs->bs->bs->b);
+    assert_not_null(bs->bs->bs->bs->b);
+    p_free_ast_Bs(bs);
+
+    input = "c";
+    p_context_init(&context, (uint8_t const *)input, strlen(input));
+    assert(p_parse_R(&context) == P_SUCCESS);
+    R * r = p_result_R(&context);
+    assert_not_null(r->c);
+    p_free_ast_R(r);
+
+    return 0;
+}
diff --git a/spec/test_starting_rules_ast.d b/spec/test_starting_rules_ast.d
new file mode 100644
index 0000000..4738132
--- /dev/null
+++ b/spec/test_starting_rules_ast.d
@@ -0,0 +1,36 @@
+import testparser;
+import std.stdio;
+import testutils;
+
+int main()
+{
+    return 0;
+}
+
+unittest
+{
+    string input = "bbbb";
+    p_context_t context;
+    p_context_init(&context, input);
+    assert(p_parse(&context) == P_SUCCESS);
+    Start * start = p_result(&context);
+    assert(start.bs);
+    assert(start.bs.b);
+    assert(start.bs.bs.b);
+    assert(start.bs.bs.bs.b);
+    assert(start.bs.bs.bs.bs.b);
+
+    p_context_init(&context, input);
+    assert(p_parse_Bs(&context) == P_SUCCESS);
+    Bs * bs = p_result_Bs(&context);
+    assert(bs.b);
+    assert(bs.bs.b);
+    assert(bs.bs.bs.b);
+    assert(bs.bs.bs.bs.b);
+
+    input = "c";
+    p_context_init(&context, input);
+    assert(p_parse_R(&context) == P_SUCCESS);
+    R * r = p_result_R(&context);
+    assert(r.c);
+}
diff --git a/spec/testutils.c b/spec/testutils.c
index 071dbd9..417fde0 100644
--- a/spec/testutils.c
+++ b/spec/testutils.c
@@ -14,6 +14,24 @@ void assert_eq_size_t_i(size_t expected, size_t actual, char const * file, size_
     }
 }
 
+void assert_ne_size_t_i(size_t expected, size_t actual, char const * file, size_t line)
+{
+    if (expected == actual)
+    {
+        fprintf(stderr, "%s:%lu: expected not %lu, got %lu\n", file, line, expected, actual);
+        assert(false);
+    }
+}
+
+void assert_not_null_i(void * ptr, char const * file, size_t line)
+{
+    if (ptr == NULL)
+    {
+        fprintf(stderr, "%s:%lu: expected not NULL\n", file, line);
+        assert(false);
+    }
+}
+
 void str_init(str_t * str, char const * cs)
 {
     size_t length = strlen(cs);
diff --git a/spec/testutils.h b/spec/testutils.h
index c93ffc9..4a402a9 100644
--- a/spec/testutils.h
+++ b/spec/testutils.h
@@ -5,6 +5,16 @@ void assert_eq_size_t_i(size_t expected, size_t actual, char const * file, size_
 #define assert_eq(expected, actual) \
     assert_eq_size_t_i(expected, actual, __FILE__, __LINE__)
 
+void assert_ne_size_t_i(size_t expected, size_t actual, char const * file, size_t line);
+
+#define assert_ne(expected, actual) \
+    assert_ne_size_t_i(expected, actual, __FILE__, __LINE__)
+
+void assert_not_null_i(void * ptr, char const * file, size_t line);
+
+#define assert_not_null(ptr) \
+    assert_not_null_i(ptr, __FILE__, __LINE__)
+
 typedef struct
 {
     char * cs;