pmt: initial 3.0.2 update

include/libgnulib/vla.h

@@ -0,0 +1,53 @@
+/* vla.h - variable length arrays
+
+   Copyright 2014-2024 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+   Written by Paul Eggert.  */
+
+/* The VLA_ELEMS macro does not allocate variable-length arrays (VLAs),
+   so it does not have the security or performance issues commonly
+   associated with VLAs.  VLA_ELEMS is for exploiting a C11 feature
+   where a function can start like this:
+
+     double scan_array (int n, double v[static n])
+
+   to require a caller to pass a vector V with at least N elements;
+   this allows better static checking and performance in some cases.
+   In C11 this feature means that V is a VLA, so the feature is
+   supported only if __STDC_NO_VLA__ is defined, and for compatibility
+   to platforms that do not support VLAs, VLA_ELEMS (n) expands to
+   nothing when __STDC_NO_VLA__ is not defined.  */
+
+/* A function's argument must point to an array with at least N elements.
+   Example: 'int main (int argc, char *argv[VLA_ELEMS (argc)]);'.  */
+
+#ifdef __STDC_NO_VLA__
+# define VLA_ELEMS(n)
+#else
+# define VLA_ELEMS(n) static n
+#endif
+
+/* Although C99 requires support for variable-length arrays (VLAs),
+   some C compilers never supported VLAs and VLAs are optional in C11.
+   VLAs are controversial because their allocation may be unintended
+   or awkward to support, and large VLAs might cause security or
+   performance problems.  GCC can diagnose the use of VLAs via the
+   -Wvla and -Wvla-larger-than warnings options, and defining the
+   macro GNULIB_NO_VLA disables the allocation of VLAs in Gnulib code.
+
+   The VLA_ELEMS macro is unaffected by GNULIB_NO_VLA, since it does
+   not allocate VLAs.  Programs that use VLA_ELEMS should be compiled
+   with 'gcc -Wvla-larger-than' instead of with 'gcc -Wvla'.  */