Build: start of a cmake-check to detect parameter-order in qsort_r

diff --git a/cmake/check_qsort_r.c b/cmake/check_qsort_r.c
new file mode 100644 (file)
index 0000000..f578f9f
--- /dev/null
+++ b/cmake/check_qsort_r.c
@@ -0,0 +1,50 @@
+/*
+Copyright (c) 2016 InternetWide.org and the ARPA2.net project
+All rights reserved. See file LICENSE for exact terms (2-clause BSD license).
+
+Adriaan de Groot <groot@kde.org>
+*/
+
+/**
+ * Test program to discover the order of parameters to qsort_r().
+ * On FreeBSD, the order is:
+ *
+ *      void qsort_r(void *base, size_t nmemb, size_t size, void *thunk,
+ *                   int (*compar)(void *, const void *, const void *));
+ * 
+ * i.e. thunk, then compar-func. On Linux (glibc), the order is:
+ * 
+ *      void qsort_r(void *base, size_t nmemb, size_t size,
+ *                  int (*compar)(const void *, const void *, void *),
+ *                  void *arg);
+ * 
+ * i.e. compar-func, then thunk (arg).
+ * 
+ * This program returns 0 if it's the Linux order, or 1 if it's the 
+ * FreeBSD parameter-order.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+
+int compar_linux(const void *p1, const void *p2, void *arg)
+{
+  return *((int *)p2) - 1;
+}
+
+int compar_freebsd(void *thunk, const void *p1, const void *p2)
+{
+  return *((int *)p1) - 1 ;
+}
+
+int main(int argc, char **argv)
+{
+  int arr[] = { 0, 1, 2 };
+  
+  /* On FreeBSD, the function is compar_freebsd, and compar_linux is passed in
+   * as thunk; on Linux / glibc, the function is compar_linux and compar_freebsd
+   * is passed in as arg.
+   */
+  qsort_r(arr, 3, sizeof(int), compar_linux, compar_freebsd);
+  
+  printf ("%d%d%d\n", arr[0], arr[1], arr[2]);
+}