xgettext: In language C, avoid stack overflow.

* gettext-tools/src/x-c.c (MAX_NESTING_DEPTH): New macro.
(nesting_depth): New variable.
(extract_parenthesized): Increase and check nesting_depth before calling
extract_parenthesized recursively.
(extract_whole_file): Initialize nesting_depth.
* gettext-tools/tests/xgettext-c-stackovfl-1: New file.
* gettext-tools/tests/xgettext-c-stackovfl-2: New file.
* gettext-tools/tests/Makefile.am (TESTS): Add them.

1 files changed, 18 insertions, 1 deletions

diff --git a/gettext-tools/src/x-c.c b/gettext-tools/src/x-c.c
index 917bd7c88..b49ddd9cc 100644
--- a/gettext-tools/src/x-c.c
+++ b/gettext-tools/src/x-c.c
@@ -1,5 +1,5 @@
 /* xgettext C/C++/ObjectiveC backend.
-   Copyright (C) 1995-1998, 2000-2009, 2012-2015, 2018-2020 Free Software Foundation, Inc.
+   Copyright (C) 1995-1998, 2000-2009, 2012-2015, 2018-2023 Free Software Foundation, Inc.
 
    This file was written by Peter Miller <millerp@canb.auug.org.au>
 
@@ -2164,6 +2164,15 @@ x_c_lex (xgettext_token_ty *tp)
 static flag_context_list_table_ty *flag_context_list_table;
 
 
+/* Maximum supported nesting depth.
+   ISO C 23 § 5.2.4.1.(1) requires 63 "nesting levels of parenthesized
+   expressions within a full expression"; then 1000 is more than enough.  */
+#define MAX_NESTING_DEPTH 1000
+
+/* Current nesting depth.  */
+static int nesting_depth;
+
+
 /* The file is broken into tokens.  Scan the token stream, looking for
    a keyword, followed by a left paren, followed by a string.  When we
    see this sequence, we have something to remember.  We assume we are
@@ -2245,6 +2254,12 @@ extract_parenthesized (message_list_ty *mlp,
           continue;
 
         case xgettext_token_type_lparen:
+          if (++nesting_depth > MAX_NESTING_DEPTH)
+            {
+              error_with_progname = false;
+              error (EXIT_FAILURE, 0, _("%s:%d: error: too many open parentheses"),
+                     logical_file_name, line_number);
+            }
           if (extract_parenthesized (mlp, inner_context, next_context_iter,
                                      arglist_parser_alloc (mlp,
                                                            state ? next_shapes : NULL)))
@@ -2252,6 +2267,7 @@ extract_parenthesized (message_list_ty *mlp,
               arglist_parser_done (argparser, arg);
               return true;
             }
+          nesting_depth--;
           next_context_iter = null_context_list_iterator;
           selectorcall_context_iter = null_context_list_iterator;
           state = 0;
@@ -2356,6 +2372,7 @@ extract_whole_file (FILE *f,
   phase6_pushback_length = 0;
 
   flag_context_list_table = flag_table;
+  nesting_depth = 0;
 
   init_keywords ();