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fix module qsort_r


From: Bruno Haible
Subject: fix module qsort_r
Date: Sun, 16 Oct 2016 22:12:14 +0200
User-agent: KMail/4.8.5 (Linux/3.8.0-44-generic; KDE/4.8.5; x86_64; ; )

Hi Paul,

The module 'qsort_r' does not work at all on systems that don't have this 
function.
For example, on AIX 7.1, with a gnulib testdir:

test-qsort_r.c: In function 'main':
test-qsort_r.c:40:3: warning: implicit declaration of function 'qsort_r' 
[-Wimplicit-function-declaration]
   qsort_r (buf, sizeof buf - 1, 1, cmp, &forward);
   ^
        gcc -mlong-double-64 -D_ALL_SOURCE -std=gnu11  -g -O2   -o test-qsort_r 
test-qsort_r.o ../gllib/libgnu.a -lm  -lm -lm -lm -lm -lm -lm -lm -lm -lm
ld: 0711-317 ERROR: Undefined symbol: .qsort_r
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.
collect2: error: ld returned 8 exit status
make: 1254-004 The error code from the last command is 1.

The problems are:
1) The gl_FUNC_QSORT_R macro finds that
     checking for qsort_r signature... GNU
2) The function does not get declared in gnulib's stdlib.h replacement.
3) It also is not included in libgnu.a (neither qsort.o nor qsort_r.o gets
   included in gl_LIBOBJS).

Ad 1) Yes really it needs an AC_CHECK_FUNC call, because a program such as
============================================================================
#define __EXTENSIONS__ 1
#define _ALL_SOURCE 1
#define _DARWIN_C_SOURCE 1
#define _GNU_SOURCE 1
#include <stdlib.h>
#define qsort_t any_nonexistent_name
                          void qsort_r (void *, size_t, size_t,
                                        int (*) (void const *, void const *,
                                                 void *),
                                        void *);
                          void (*p) (void *, size_t, size_t,
                                     int (*) (void const *, void const *,
                                              void *),
                                     void *) = qsort_r;
int main () { return 0; }
============================================================================
compiles and links perfectly fine.

Ad 2) The idiom in stdlib.h is incomplete. You need to pick the complete one
(e.g. copy&paste from the 'ptsname_r' declaration).

Additionally:
4) The qsort_r function would not be warned about in GNULIB_POSIXCHECK mode.

Here's a proposed fix.


2016-10-16  Bruno Haible  <address@hidden>

        qsort_r: Fix macrology for platforms that lack the function.
        * m4/stdlib_h.m4 (gl_STDLIB_H): Check for qsort_r.
        (gl_STDLIB_H_DEFAULTS): Initialize HAVE_QSORT_R.
        * modules/stdlib (Makefile.am): Substitute HAVE_QSORT_R.
        * lib/stdlib.in.h (qsort_r): Provide declaration if the function does
        not exist.
        * m4/qsort_r.m4 (gl_FUNC_QSORT_R): Use AC_CHECK_FUNCS to test whether
        the function exists.
        * modules/qsort_r: Add comments.

diff --git a/lib/stdlib.in.h b/lib/stdlib.in.h
index 70dc88d..db3253b 100644
--- a/lib/stdlib.in.h
+++ b/lib/stdlib.in.h
@@ -521,6 +521,9 @@ _GL_CXXALIASWARN (putenv);
 #endif
 
 #if @GNULIB_QSORT_R@
+/* Sort an array of NMEMB elements, starting at address BASE, each element
+   occupying SIZE bytes, in ascending order according to the comparison
+   function COMPARE.  */
 # if @REPLACE_QSORT_R@
 #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
 #   undef qsort_r
@@ -535,12 +538,24 @@ _GL_CXXALIAS_RPL (qsort_r, void, (void *base, size_t 
nmemb, size_t size,
                                                   void *),
                                   void *arg));
 # else
+#  if address@hidden@
+_GL_FUNCDECL_SYS (qsort_r, void, (void *base, size_t nmemb, size_t size,
+                                  int (*compare) (void const *, void const *,
+                                                  void *),
+                                  void *arg) _GL_ARG_NONNULL ((1, 4)));
+#  endif
 _GL_CXXALIAS_SYS (qsort_r, void, (void *base, size_t nmemb, size_t size,
                                   int (*compare) (void const *, void const *,
                                                   void *),
                                   void *arg));
 # endif
 _GL_CXXALIASWARN (qsort_r);
+#elif defined GNULIB_POSIXCHECK
+# undef qsort_r
+# if HAVE_RAW_DECL_QSORT_R
+_GL_WARN_ON_USE (qsort_r, "qsort_r is not portable - "
+                 "use gnulib module qsort_r for portability");
+# endif
 #endif
 
 
diff --git a/m4/qsort_r.m4 b/m4/qsort_r.m4
index f3d2927..f1de7d4 100644
--- a/m4/qsort_r.m4
+++ b/m4/qsort_r.m4
@@ -14,35 +14,39 @@ AC_DEFUN([gl_FUNC_QSORT_R],
 
   AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
 
-  AC_CACHE_CHECK([for qsort_r signature], [gl_cv_qsort_r_signature],
-    [AC_LINK_IFELSE(
-       [AC_LANG_PROGRAM([[#include <stdlib.h>
-                          void qsort_r (void *, size_t, size_t,
-                                        int (*) (void const *, void const *,
-                                                 void *),
-                                        void *);
-                          void (*p) (void *, size_t, size_t,
-                                     int (*) (void const *, void const *,
-                                              void *),
-                                     void *) = qsort_r;
-                        ]])],
-       [gl_cv_qsort_r_signature=GNU],
-       [AC_LINK_IFELSE(
-          [AC_LANG_PROGRAM([[#include <stdlib.h>
-                             void qsort_r (void *, size_t, size_t, void *,
-                                           int (*) (void *,
-                                                    void const *,
-                                                    void const *));
-                             void (*p) (void *, size_t, size_t, void *,
-                                        int (*) (void *, void const *,
-                                                 void const *)) = qsort_r;
-                           ]])],
-          [gl_cv_qsort_r_signature=BSD],
-          [gl_cv_qsort_r_signature=no])])])
-
-  case $gl_cv_qsort_r_signature in
-    GNU) HAVE_QSORT_R=1;;
-    BSD) HAVE_QSORT_R=1 REPLACE_QSORT_R=1;;
-    *)   HAVE_QSORT_R=0 REPLACE_QSORT_R=1;;
-  esac
+  AC_CHECK_FUNCS_ONCE([qsort_r])
+  if test $ac_cv_func_qsort_r = yes; then
+    AC_CACHE_CHECK([for qsort_r signature], [gl_cv_qsort_r_signature],
+      [AC_LINK_IFELSE(
+         [AC_LANG_PROGRAM([[#include <stdlib.h>
+                            void qsort_r (void *, size_t, size_t,
+                                          int (*) (void const *, void const *,
+                                                   void *),
+                                          void *);
+                            void (*p) (void *, size_t, size_t,
+                                       int (*) (void const *, void const *,
+                                                void *),
+                                       void *) = qsort_r;
+                          ]])],
+         [gl_cv_qsort_r_signature=GNU],
+         [AC_LINK_IFELSE(
+            [AC_LANG_PROGRAM([[#include <stdlib.h>
+                               void qsort_r (void *, size_t, size_t, void *,
+                                             int (*) (void *,
+                                                      void const *,
+                                                      void const *));
+                               void (*p) (void *, size_t, size_t, void *,
+                                          int (*) (void *, void const *,
+                                                   void const *)) = qsort_r;
+                             ]])],
+            [gl_cv_qsort_r_signature=BSD],
+            [gl_cv_qsort_r_signature=unknown])])])
+    case $gl_cv_qsort_r_signature in
+      GNU)     ;;
+      BSD)     REPLACE_QSORT_R=1 ;;
+      unknown) HAVE_QSORT_R=0 REPLACE_QSORT_R=1 ;;
+    esac
+  else
+    HAVE_QSORT_R=0
+  fi
 ])
diff --git a/m4/stdlib_h.m4 b/m4/stdlib_h.m4
index 19107c4..3999068 100644
--- a/m4/stdlib_h.m4
+++ b/m4/stdlib_h.m4
@@ -1,4 +1,4 @@
-# stdlib_h.m4 serial 42
+# stdlib_h.m4 serial 43
 dnl Copyright (C) 2007-2016 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -21,7 +21,7 @@ AC_DEFUN([gl_STDLIB_H],
 #endif
     ]], [_Exit atoll canonicalize_file_name getloadavg getsubopt grantpt
     initstate initstate_r mkdtemp mkostemp mkostemps mkstemp mkstemps
-    posix_openpt ptsname ptsname_r random random_r realpath rpmatch
+    posix_openpt ptsname ptsname_r qsort_r random random_r realpath rpmatch
     secure_getenv setenv setstate setstate_r srandom srandom_r
     strtod strtoll strtoull unlockpt unsetenv])
 ])
@@ -85,6 +85,7 @@ AC_DEFUN([gl_STDLIB_H_DEFAULTS],
   HAVE_POSIX_OPENPT=1;       AC_SUBST([HAVE_POSIX_OPENPT])
   HAVE_PTSNAME=1;            AC_SUBST([HAVE_PTSNAME])
   HAVE_PTSNAME_R=1;          AC_SUBST([HAVE_PTSNAME_R])
+  HAVE_QSORT_R=1;            AC_SUBST([HAVE_QSORT_R])
   HAVE_RANDOM=1;             AC_SUBST([HAVE_RANDOM])
   HAVE_RANDOM_H=1;           AC_SUBST([HAVE_RANDOM_H])
   HAVE_RANDOM_R=1;           AC_SUBST([HAVE_RANDOM_R])
diff --git a/modules/qsort_r b/modules/qsort_r
index 52b57c0..6772edc 100644
--- a/modules/qsort_r
+++ b/modules/qsort_r
@@ -13,8 +13,10 @@ stdlib
 configure.ac:
 gl_FUNC_QSORT_R
 if test $HAVE_QSORT_R = 0; then
+  # The function is missing from the system or has an unknown signature.
   AC_LIBOBJ([qsort])
 elif test $REPLACE_QSORT_R = 1; then
+  # The function exists, but it has the BSD signature.
   AC_LIBOBJ([qsort_r])
 fi
 gl_STDLIB_MODULE_INDICATOR([qsort_r])
diff --git a/modules/stdlib b/modules/stdlib
index cbc5b01..27b1caa 100644
--- a/modules/stdlib
+++ b/modules/stdlib
@@ -79,6 +79,7 @@ stdlib.h: stdlib.in.h $(top_builddir)/config.status 
$(CXXDEFS_H) \
              -e 's|@''HAVE_POSIX_OPENPT''@|$(HAVE_POSIX_OPENPT)|g' \
              -e 's|@''HAVE_PTSNAME''@|$(HAVE_PTSNAME)|g' \
              -e 's|@''HAVE_PTSNAME_R''@|$(HAVE_PTSNAME_R)|g' \
+             -e 's|@''HAVE_QSORT_R''@|$(HAVE_QSORT_R)|g' \
              -e 's|@''HAVE_RANDOM''@|$(HAVE_RANDOM)|g' \
              -e 's|@''HAVE_RANDOM_H''@|$(HAVE_RANDOM_H)|g' \
              -e 's|@''HAVE_RANDOM_R''@|$(HAVE_RANDOM_R)|g' \




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