1 files changed, 104 insertions, 0 deletions
diff --git a/m4/strncat.m4 b/m4/strncat.m4
new file mode 100644
index 0000000..b38ade6
--- /dev/null
+++ b/m4/strncat.m4
@@ -0,0 +1,104 @@
+# strncat.m4 serial 4
+dnl Copyright (C) 2002-2004, 2009-2020 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN_ONCE([gl_FUNC_STRNCAT],
+[
+  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+
+  dnl Check for prerequisites for memory fence checks.
+  gl_FUNC_MMAP_ANON
+  AC_CHECK_HEADERS_ONCE([sys/mman.h])
+  AC_CHECK_FUNCS_ONCE([mprotect])
+
+  dnl Detect bug in Solaris 8..10 on SPARC and Solaris 11.0 on x86:
+  dnl strncat should not dereference more than n bytes, but always dereferences
+  dnl n+1 bytes if the first n bytes don't contain a NUL byte.
+  dnl Assume that strncat works on platforms that lack mprotect.
+  AC_CACHE_CHECK([whether strncat works], [gl_cv_func_strncat_works],
+    [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <string.h>
+#if HAVE_SYS_MMAN_H
+# include <fcntl.h>
+# include <unistd.h>
+# include <sys/types.h>
+# include <sys/mman.h>
+# ifndef MAP_FILE
+#  define MAP_FILE 0
+# endif
+#endif
+]], [[
+  char *fence = NULL;
+#if HAVE_SYS_MMAN_H && HAVE_MPROTECT
+# if HAVE_MAP_ANONYMOUS
+  const int flags = MAP_ANONYMOUS | MAP_PRIVATE;
+  const int fd = -1;
+# else /* !HAVE_MAP_ANONYMOUS */
+  const int flags = MAP_FILE | MAP_PRIVATE;
+  int fd = open ("/dev/zero", O_RDONLY, 0666);
+  if (fd >= 0)
+# endif
+    {
+      int pagesize = getpagesize ();
+      char *two_pages =
+        (char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE,
+                       flags, fd, 0);
+      if (two_pages != (char *)(-1)
+          && mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0)
+        fence = two_pages + pagesize;
+    }
+#endif
+  if (fence)
+    {
+      char dest[8];
+
+      dest[0] = '*';
+      dest[1] = 'a';
+      dest[2] = '\0';
+      dest[3] = 'w';
+      dest[4] = 'x';
+      dest[5] = 'y';
+      dest[6] = 'z';
+
+      *(fence - 3) = '7';
+      *(fence - 2) = '2';
+      *(fence - 1) = '9';
+
+      if (strncat (dest + 1, fence - 3, 3) != dest + 1)
+        return 1;
+      if (dest[0] != '*')
+        return 2;
+      if (dest[1] != 'a'
+          || dest[2] != '7' || dest[3] != '2' || dest[4] != '9'
+          || dest[5] != '\0')
+        return 3;
+      if (dest[6] != 'z')
+        return 4;
+    }
+  return 0;
+]])], [gl_cv_func_strncat_works=yes], [gl_cv_func_strncat_works=no],
+       [
+        case "$host_os" in
+                    # Guess no on Solaris.
+          solaris*) gl_cv_func_strncat_works="guessing no" ;;
+                    # Guess yes on native Windows.
+          mingw*)   gl_cv_func_strncat_works="guessing yes" ;;
+                    # Guess yes otherwise.
+          *)        gl_cv_func_strncat_works="guessing yes" ;;
+        esac
+       ])
+    ])
+  case "$gl_cv_func_strncat_works" in
+    *yes) ;;
+    *) REPLACE_STRNCAT=1 ;;
+  esac
+])
+
+# Prerequisites of lib/strncat.c.
+AC_DEFUN([gl_PREREQ_STRNCAT], [
+  :
+])