regex: copy back from Gnulib

Copy regex-related files back from Gnulib, to fix a problem with
static checking of regex calls noted by Martin Sebor.  This merges the
following changes:

* New macro __attribute_nonnull__ in misc/sys/cdefs.h, for use later
when copying other files back from Gnulib.

* Use __GNULIB_CDEFS instead of __GLIBC__ when deciding
whether to include bits/wordsize.h etc.

* Avoid duplicate entries in epsilon closure table.

* New regex.h macro _REGEX_NELTS to let regexec say that its pmatch
arg should contain nmatch elts.  Use that for regexec, instead of
__attr_access (which is incorrect).

* New regex.h macro _Attr_access_ which is like __attr_access except
portable to non-glibc platforms.

* Add some DEBUG_ASSERTs to pacify gcc -fanalyzer and to catch
recently-fixed performance bugs if they recur.

* Add Gnulib-specific stuff to port the dynarray- and lock-using parts
of regex code to non-glibc platforms.

* Fix glibc bug 11053.

* Avoid some undefined behavior when popping an empty fail stack.

1 files changed, 9 insertions, 1 deletions

diff --git a/posix/regex_internal.c b/posix/regex_internal.c
index 9dd387ef85..aefcfa2f52 100644
--- a/posix/regex_internal.c
+++ b/posix/regex_internal.c
@@ -1211,6 +1211,10 @@ re_node_set_merge (re_node_set *dest, const re_node_set *src)
 
   if (__glibc_unlikely (dest->nelem == 0))
     {
+      /* Although we already guaranteed above that dest->alloc != 0 and
+         therefore dest->elems != NULL, add a debug assertion to pacify
+         GCC 11.2.1's -fanalyzer.  */
+      DEBUG_ASSERT (dest->elems);
       dest->nelem = src->nelem;
       memcpy (dest->elems, src->elems, src->nelem * sizeof (Idx));
       return REG_NOERROR;
@@ -1286,7 +1290,10 @@ re_node_set_insert (re_node_set *set, Idx elem)
 
   if (__glibc_unlikely (set->nelem) == 0)
     {
-      /* We already guaranteed above that set->alloc != 0.  */
+      /* Although we already guaranteed above that set->alloc != 0 and
+         therefore set->elems != NULL, add a debug assertion to pacify
+         GCC 11.2 -fanalyzer.  */
+      DEBUG_ASSERT (set->elems);
       set->elems[0] = elem;
       ++set->nelem;
       return true;
@@ -1314,6 +1321,7 @@ re_node_set_insert (re_node_set *set, Idx elem)
     {
       for (idx = set->nelem; set->elems[idx - 1] > elem; idx--)
 	set->elems[idx] = set->elems[idx - 1];
+      DEBUG_ASSERT (set->elems[idx - 1] < elem);
     }
 
   /* Insert the new element.  */