[PATCH v3] argp-help: Get rid of alloca.

[Joe Simmons-Talbott <josimmon@redhat.com>]

Replace alloca with malloc and a scratch_buffer to avoid potential stack
overflow.

Checked on x86_64-linux-gnu
---
 argp/argp-help.c | 40 ++++++++++++++++++++++------------------
 1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/argp/argp-help.c b/argp/argp-help.c
index d019ed58d2..54a15a8233 100644
--- a/argp/argp-help.c
+++ b/argp/argp-help.c
@@ -25,21 +25,7 @@
 #include <config.h>
 #endif
 
-/* AIX requires this to be the first thing in the file.  */
-#ifndef __GNUC__
-# if HAVE_ALLOCA_H || defined _LIBC
-#  include <alloca.h>
-# else
-#  ifdef _AIX
-#pragma alloca
-#  else
-#   ifndef alloca /* predefined by HP cc +Olibcalls */
-char *alloca ();
-#   endif
-#  endif
-# endif
-#endif
-
+#include <scratch_buffer.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdlib.h>
@@ -1450,8 +1436,14 @@ hol_usage (struct hol *hol, argp_fmtstream_t stream)
     {
       unsigned nentries;
       struct hol_entry *entry;
-      char *short_no_arg_opts = alloca (strlen (hol->short_options) + 1);
-      char *snao_end = short_no_arg_opts;
+      char *short_no_arg_opts;
+      char *snao_end;
+
+      short_no_arg_opts = malloc (strlen (hol->short_options) + 1);
+      assert (short_no_arg_opts != NULL);
+
+      snao_end = short_no_arg_opts;
+	
 
       /* First we put a list of short options without arguments.  */
       for (entry = hol->entries, nentries = hol->num_entries
@@ -1478,6 +1470,8 @@ hol_usage (struct hol *hol, argp_fmtstream_t stream)
 	   ; entry++, nentries--)
 	hol_entry_long_iterate (entry, usage_long_opt,
 				entry->argp->argp_domain, stream);
+
+      free (short_no_arg_opts);
     }
 }
 \f
@@ -1698,7 +1692,15 @@ _help (const struct argp *argp, const struct argp_state *state, FILE *stream,
     {
       int first_pattern = 1, more_patterns;
       size_t num_pattern_levels = argp_args_levels (argp);
-      char *pattern_levels = alloca (num_pattern_levels);
+      struct scratch_buffer buf;
+      scratch_buffer_init (&buf);
+      char *pattern_levels;
+      bool result;
+
+      result = scratch_buffer_set_array_size (&buf, 1, num_pattern_levels);
+      assert (result);
+
+      pattern_levels = buf.data;
 
       memset (pattern_levels, 0, num_pattern_levels);
 
@@ -1746,6 +1748,8 @@ _help (const struct argp *argp, const struct argp_state *state, FILE *stream,
 	  first_pattern = 0;
 	}
       while (more_patterns);
+
+      scratch_buffer_free (&buf);
     }
 
   if (flags & ARGP_HELP_PRE_DOC)
-- 
2.39.2