libctf: look for BSD versus GNU qsort_r signatures

We cannot just look for any declaration of qsort_r, because some
operating systems have a qsort_r that has a different prototype
but which still has a pair of pointers in the right places (the last two
args are interchanged): so use AC_LINK_IFELSE to check for both
known variants of qsort_r(), and swap their args into a consistent order
in a suitable inline function.  (The code for this is taken almost
unchanged from gnulib.)

(Now we are not using AC_LIBOBJ any more, we can use a better name for
the qsort_r replacement as well.)

libctf/
	* qsort_r.c: Rename to...
	* ctf-qsort_r.c: ... this.
	(_quicksort): Define to ctf_qsort_r.
	* ctf-decls.h (qsort_r): Remove.
	(ctf_qsort_r): Add.
	(struct ctf_qsort_arg): New, transport the real ARG and COMPAR.
	(ctf_qsort_compar_thunk): Rearrange the arguments to COMPAR.
	* Makefile.am (libctf_a_LIBADD): Remove.
	(libctf_a_SOURCES): New, add ctf-qsort_r.c.
	* ctf-archive.c (ctf_arc_write): Call ctf_qsort_r, not qsort_r.
	* ctf-create.c (ctf_update): Likewise.
	* configure.ac: Check for BSD versus GNU qsort_r signature.
	* Makefile.in: Regenerate.
	* config.h.in: Likewise.
	* configure: Likewise.

1 files changed, 36 insertions, 3 deletions

diff --git a/libctf/ctf-decls.h b/libctf/ctf-decls.h
index 5e9ede4..d12409e 100644
--- a/libctf/ctf-decls.h
+++ b/libctf/ctf-decls.h
@@ -22,12 +22,45 @@
 
 #include "config.h"
 
-#if !HAVE_DECL_QSORT_R
 #include <stddef.h>
-void qsort_r (void *base, size_t nmemb, size_t size,
+#include <stdlib.h>
+
+#if HAVE_QSORT_R_ARG_LAST
+static inline void
+ctf_qsort_r (void *base, size_t nmemb, size_t size,
+	     int (*compar)(const void *, const void *, void *),
+	     void *arg)
+{
+  qsort_r (base, nmemb, size, compar, arg);
+}
+#elif HAVE_QSORT_R_COMPAR_LAST
+struct ctf_qsort_arg
+{
+  int (*compar) (const void *, const void *, void *);
+  void *arg;
+};
+
+static int
+ctf_qsort_compar_thunk (void *arg, const void *a, const void *b)
+{
+  struct ctf_qsort_arg *qsort_arg = (struct ctf_qsort_arg *) arg;
+
+  return qsort_arg->compar (a, b, arg);
+}
+
+static inline void
+ctf_qsort_r (void *base, size_t nmemb, size_t size,
+	     int (*compar)(const void *, const void *, void *),
+	     void *arg)
+{
+  struct ctf_qsort_arg thunk = { compar, arg };
+  qsort_r (base, nmemb, size, &thunk, ctf_qsort_compar_thunk);
+}
+#else
+void ctf_qsort_r (void *base, size_t nmemb, size_t size,
 	      int (*compar)(const void *, const void *, void *),
 	      void *arg);
-#endif /* !HAVE_DECL_QSORT_R */
+#endif
 
 #undef MAX
 #undef MIN