Vector-sorting fixes.

It's not safe to call qsort or qsort_r, since they have undefined
behavior if the user-specified predicate is not a total order.
Also, watch out for garbage-collection while sorting vectors.
* admin/merge-gnulib (GNULIB_MODULES): Add vla.
* configure.ac (qsort_r): Remove, as we no longer use qsort-like
functions.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* lib/vla.h, m4/vararrays.m4: New files, copied from gnulib.
* lib/stdlib.in.h, m4/stdlib_h.m4: Sync from gnulib, incorporating:
2014-08-29 qsort_r: new module, for GNU-style qsort_r
The previous two files' changes are boilerplate generated by
admin/merge-gnulib, and should not affect Emacs.
* src/fns.c: Include <vla.h>.
(sort_vector_predicate) [!HAVE_QSORT_R]: Remove.
(sort_vector_compare): Remove, replacing with ....
(inorder, merge_vectors, sort_vector_inplace, sort_vector_copy):
... these new functions.
(sort_vector): Rewrite to use the new functions.
GCPRO locals, since the predicate can invoke the GC.
Since it's in-place return void; caller changed.
(merge): Use 'inorder', for clarity.

Fixes: debbugs:18361

3 files changed, 75 insertions, 0 deletions

diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 98acc069c9..7b6b5c00f9 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -146,7 +146,9 @@ AC_DEFUN([gl_EARLY],
   # Code from module unsetenv:
   # Code from module update-copyright:
   # Code from module utimens:
+  # Code from module vararrays:
   # Code from module verify:
+  # Code from module vla:
   # Code from module warnings:
   # Code from module xalloc-oversized:
 ])
@@ -383,6 +385,7 @@ AC_DEFUN([gl_INIT],
   fi
   gl_STDLIB_MODULE_INDICATOR([unsetenv])
   gl_UTIMENS
+  AC_C_VARARRAYS
   gl_gnulib_enabled_260941c0e5dc67ec9e87d1fb321c300b=false
   gl_gnulib_enabled_dosname=false
   gl_gnulib_enabled_euidaccess=false
@@ -916,6 +919,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/utimens.c
   lib/utimens.h
   lib/verify.h
+  lib/vla.h
   lib/xalloc-oversized.h
   m4/00gnulib.m4
   m4/absolute-header.m4
@@ -1013,6 +1017,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/utimbuf.m4
   m4/utimens.m4
   m4/utimes.m4
+  m4/vararrays.m4
   m4/warn-on-use.m4
   m4/warnings.m4
   m4/wchar_t.m4
diff --git a/m4/stdlib_h.m4 b/m4/stdlib_h.m4
index 03b448b94f..86aff16eb0 100644
--- a/m4/stdlib_h.m4
+++ b/m4/stdlib_h.m4
@@ -55,6 +55,7 @@ AC_DEFUN([gl_STDLIB_H_DEFAULTS],
   GNULIB_PTSNAME=0;       AC_SUBST([GNULIB_PTSNAME])
   GNULIB_PTSNAME_R=0;     AC_SUBST([GNULIB_PTSNAME_R])
   GNULIB_PUTENV=0;        AC_SUBST([GNULIB_PUTENV])
+  GNULIB_QSORT_R=0;       AC_SUBST([GNULIB_QSORT_R])
   GNULIB_RANDOM=0;        AC_SUBST([GNULIB_RANDOM])
   GNULIB_RANDOM_R=0;      AC_SUBST([GNULIB_RANDOM_R])
   GNULIB_REALLOC_POSIX=0; AC_SUBST([GNULIB_REALLOC_POSIX])
@@ -107,6 +108,7 @@ AC_DEFUN([gl_STDLIB_H_DEFAULTS],
   REPLACE_PTSNAME=0;         AC_SUBST([REPLACE_PTSNAME])
   REPLACE_PTSNAME_R=0;       AC_SUBST([REPLACE_PTSNAME_R])
   REPLACE_PUTENV=0;          AC_SUBST([REPLACE_PUTENV])
+  REPLACE_QSORT_R=0;         AC_SUBST([REPLACE_QSORT_R])
   REPLACE_RANDOM_R=0;        AC_SUBST([REPLACE_RANDOM_R])
   REPLACE_REALLOC=0;         AC_SUBST([REPLACE_REALLOC])
   REPLACE_REALPATH=0;        AC_SUBST([REPLACE_REALPATH])
diff --git a/m4/vararrays.m4 b/m4/vararrays.m4
new file mode 100644
index 0000000000..cbda525c75
--- /dev/null
+++ b/m4/vararrays.m4
@@ -0,0 +1,68 @@
+# Check for variable-length arrays.
+
+# serial 5
+
+# From Paul Eggert
+
+# Copyright (C) 2001, 2009-2014 Free Software Foundation, Inc.
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# This is a copy of AC_C_VARARRAYS from a recent development version
+# of Autoconf.  It replaces Autoconf's version, or for pre-2.61 autoconf
+# it defines the macro that Autoconf lacks.
+AC_DEFUN([AC_C_VARARRAYS],
+[
+  AC_CACHE_CHECK([for variable-length arrays],
+    ac_cv_c_vararrays,
+    [AC_EGREP_CPP([defined],
+       [#ifdef __STDC_NO_VLA__
+	defined
+	#endif
+       ],
+       [ac_cv_c_vararrays='no: __STDC_NO_VLA__ is defined'],
+       [AC_COMPILE_IFELSE(
+	  [AC_LANG_PROGRAM(
+	     [[/* Test for VLA support.  This test is partly inspired
+		  from examples in the C standard.  Use at least two VLA
+		  functions to detect the GCC 3.4.3 bug described in:
+		  http://lists.gnu.org/archive/html/bug-gnulib/2014-08/msg00014.html
+		  */
+	       #ifdef __STDC_NO_VLA__
+		syntax error;
+	       #else
+		 extern int n;
+		 int B[100];
+		 int fvla (int m, int C[m][m]);
+
+		 int
+		 simple (int count, int all[static count])
+		 {
+		   return all[count - 1];
+		 }
+
+		 int
+		 fvla (int m, int C[m][m])
+		 {
+		   typedef int VLA[m][m];
+		   VLA x;
+		   int D[m];
+		   static int (*q)[m] = &B;
+		   int (*s)[n] = q;
+		   return C && &x[0][0] == &D[0] && &D[0] == s[0];
+		 }
+	       #endif
+	       ]])],
+	  [ac_cv_c_vararrays=yes],
+	  [ac_cv_c_vararrays=no])])])
+  if test "$ac_cv_c_vararrays" = yes; then
+    dnl This is for compatibility with Autoconf 2.61-2.69.
+    AC_DEFINE([HAVE_C_VARARRAYS], 1,
+      [Define to 1 if C supports variable-length arrays.])
+  elif test "$ac_cv_c_vararrays" = no; then
+    AC_DEFINE([__STDC_NO_VLA__], 1,
+      [Define to 1 if C does not support variable-length arrays, and
+       if the compiler does not already define this.])
+  fi
+])