Fix typedef/variable name conflict: add declarator_init_start rule to register identifier before parsing initializer

Co-authored-by: michael-schwarz <13812333+michael-schwarz@users.noreply.github.com>

Author: Copilot

src/frontc/cparser.mly

@@ -388,7 +388,7 @@ let transformOffsetOf (speclist, dtype) member =
 
 %type <Cabs.init_name> init_declarator
 %type <Cabs.init_name list> init_declarator_list
-%type <Cabs.name> declarator
+%type <Cabs.name> declarator declarator_init_start
 %type <Cabs.name * expression option> field_decl
 %type <(Cabs.name * expression option) list> field_decl_list
 %type <string * Cabs.decl_type> direct_decl
@@ -1037,8 +1037,15 @@ init_declarator_attr:
 ;
 init_declarator:                             /* ISO 6.7 */
     declarator                          { ($1, NO_INIT) }
-|   declarator EQ init_expression location
-                                        { let (n, d, a, l) = $1 in ((n, d, a, joinLoc l $4), $3) }
+|   declarator_init_start init_expression location
+                                        { let (n, d, a, l) = $1 in ((n, d, a, joinLoc l $3), $2) }
+;
+
+(* Parses "declarator =" and adds the declared name as a variable identifier
+   in the lexer hack, so that in the initializer the name shadows any typedef
+   with the same name (C11 6.2.1.7: scope begins after completion of declarator). *)
+declarator_init_start:
+    declarator EQ                       { let (n, _, _, _) = $1 in !Lexerhack.add_identifier n; $1 }
 ;
 
 decl_spec_list_common:                  /* ISO 6.7 */

test/small1/typedef_varname.c

@@ -0,0 +1,25 @@
+/* Test for typedef and variable name conflict (issue #114).
+   A variable with the same name as a typedef should shadow it in its initializer,
+   per C11 6.2.1.7: "Any other identifier has scope that begins just after the
+   completion of its declarator." */
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef struct raxNode {
+    uint32_t iskey:1;
+    uint32_t isnull:1;
+    uint32_t iscompr:1;
+    uint32_t size:29;
+    unsigned char data[];
+} raxNode;
+
+typedef struct rax {
+    raxNode *head;
+    uint64_t numele;
+    uint64_t numnodes;
+} rax;
+
+int main() {
+  rax *rax = malloc(sizeof(*rax)); /* variable rax shadows typedef rax in initializer */
+  return rax == 0;
+}

test/testcil.pl

@@ -471,6 +471,7 @@ sub addToGroup {
 addTest("testrun/for1 ");
 addTest("testrun/void _GNUCC=1");
 addTest("test/voidtypedef ");
+addTest("testrun/typedef_varname ");
 addTest("testrun/wrongnumargs ");
 addBadComment("testrun/wrongnumargs",
                         "Notbug. Should fail since we don't pad argument lists");