Step 3 of the switch to support configuration with NPTL:

Change "configure.in".

The branches for Tru64 (ex: OSF/1) and Linux are separated,
and for Linux 'getconf GNU_LIBPTHREAD_VERSION' is used to tell between Linuxthreads and NPTL.


configure.in:
  Step 3 of the switch to support configuration with NPTL:
  Change "configure.in".
  
  1) Separate the branches checking for thread libraries on OSF/1 (now: Tru64) and on Linux,
     as these are different things. In the Tru64 branch, remove the obsolete part for OSF/1 3.2,
     because that is gone since long (about a decade?); we are at 5 now. Adapt the comment.
  
  2) For Linux, the thread libraries are "Linuxthreads" (older) and "NPTL" (newer).
     Until now, we cared only about "Linuxthreads", and we did so by checking a comment in 
     the header file '/usr/include/pthread.h'.
     With NPTL as an alternative or only thread package, this is not secure any more,
     there are distributions where the header file still contains that comment but the lib is NPTL.
     For all current distributions, the way to check is the 'getconf' command.
  
     On old distributions, 'getconf' exists but does not understand the 'GNU_LIBPTHREAD_VERSION'
     parameter. It is unlikely that such an old system should have NPTL, so the header file check is
     sufficient if the getconf inquiry fails.
  
     For both Linuxthreads and NPTL, '-lpthread' is the linker option to use.
  
  3) To detect problems as early as possible, on Linux a link test using '-lpthread' is done.
     The code is copied from a later check where the thread functions are searched in '-lc',
     '-lpthread', and '-lpthreads', but this later search would not be executed after the lib
     was already determined. So if the test is not done here, it will be detected only during
     the real build. This is too late.

configure.in

@@ -411,12 +411,12 @@ if expr "$target_os" : "[[Ll]]inux.*" > /dev/null
 then
   MYSQLD_DEFAULT_SWITCHES="--skip-locking"
   TARGET_LINUX="true"
-  AC_MSG_RESULT("yes");
+  AC_MSG_RESULT("yes")
   AC_DEFINE([TARGET_OS_LINUX], [1], [Whether we build for Linux])
 else
   MYSQLD_DEFAULT_SWITCHES=""
   TARGET_LINUX="false"
-  AC_MSG_RESULT("no");
+  AC_MSG_RESULT("no")
 fi
 AC_SUBST(MYSQLD_DEFAULT_SWITCHES)
 AC_SUBST(TARGET_LINUX)
@@ -1267,11 +1267,36 @@ esac
 # We have to check libc last because else it fails on Solaris 2.6
 
 with_posix_threads="no"
-# Hack for DEC-UNIX (OSF1)
+# Search thread lib on Linux
 if test "$with_named_thread" = "no" -a "$with_mit_threads" = "no"
 then
+    AC_MSG_CHECKING("Linux threads")
+    if test "$TARGET_LINUX" = "true"
+    then
+        AC_MSG_RESULT("starting")
+        # use getconf to check glibc contents
+        AC_MSG_CHECKING("getconf GNU_LIBPTHREAD_VERSION")
+        case `getconf GNU_LIBPTHREAD_VERSION | tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ` in
+        NPTL* )
+                AC_MSG_RESULT("NPTL")
+                AC_DEFINE([HAVE_NPTL], [1], [NPTL threads implementation])
+                with_named_thread="-lpthread"
+                ;;
+        LINUXTHREADS* )
+                AC_MSG_RESULT("Linuxthreads")
+                AC_DEFINE([HAVE_LINUXTHREADS], [1], 
+                      [Whether we are using Xavier Leroy's LinuxThreads])
+                with_named_thread="-lpthread"
+                ;;
+        * )
+                AC_MSG_RESULT("unknown")
+                ;;
+        esac
+        if test "$with_named_thread" = "no"
+        then
+          # old method, check headers
           # Look for LinuxThreads.
-  AC_MSG_CHECKING("LinuxThreads")
+          AC_MSG_CHECKING("LinuxThreads in header file comment")
           res=`grep Linuxthreads /usr/include/pthread.h 2>/dev/null | wc -l`
           if test "$res" -gt 0
           then
@@ -1287,41 +1312,48 @@ then
           else
             AC_MSG_RESULT("Not found")
             # If this is a linux machine we should barf
-      if test "$TARGET_LINUX" = "true"
-      then
-	AC_MSG_ERROR([This is a linux system and Linuxthreads was not
-found. On linux Linuxthreads should be used.  Please install Linuxthreads
-(or a new glibc) and try again.  See the Installation chapter in the
-Reference Manual for more information.])
+            AC_MSG_ERROR([This is a Linux system without a working getconf, 
+and Linuxthreads was not found. Please install it (or a new glibc) and try again.  
+See the Installation chapter in the Reference Manual for more information.])
+          fi
+        else
+            AC_MSG_RESULT("no need to check headers")
+        fi
+        
+        AC_MSG_CHECKING("for pthread_create in -lpthread");
+        ac_save_LIBS="$LIBS"
+        LIBS="$LIBS -lpthread"
+        AC_TRY_LINK( [#include <pthread.h>],
+              [ (void) pthread_create((pthread_t*) 0,(pthread_attr_t*) 0, 0, 0); ],
+              AC_MSG_RESULT("yes"),
+              [ AC_MSG_RESULT("no")
+                AC_MSG_ERROR([
+This is a Linux system claiming to support threads, either Linuxthreads or NPTL, but linking a test program failed.  
+Please install one of these (or a new glibc) and try again.  
+See the Installation chapter in the Reference Manual for more information.]) ]
+              )
+        LIBS="$ac_save_LIBS"
     else
-	AC_MSG_CHECKING("DEC threads")
+        AC_MSG_RESULT("no")
+    fi  # "$TARGET_LINUX" 
+fi  # "$with_named_thread" = "no" -a "$with_mit_threads" = "no"
+
+
+# Hack for DEC-UNIX (OSF1 -> Tru64)
+if test "$with_named_thread" = "no" -a "$with_mit_threads" = "no"
+then
+    AC_MSG_CHECKING("DEC threads post OSF/1 3.2")
     if test -f /usr/shlib/libpthread.so -a -f /usr/lib/libmach.a -a -f /usr/ccs/lib/cmplrs/cc/libexc.a
     then
       with_named_thread="-lpthread -lmach -lexc"
       CFLAGS="$CFLAGS -D_REENTRANT"
       CXXFLAGS="$CXXFLAGS -D_REENTRANT"
-	  AC_DEFINE(HAVE_DEC_THREADS, [1],
-                    [Whether we are using DEC threads])
-	  AC_MSG_RESULT("yes")
-	else
-	  AC_MSG_RESULT("no")
-	  AC_MSG_CHECKING("DEC 3.2 threads")
-          if test -f /usr/shlib/libpthreads.so -a -f /usr/lib/libmach.a -a -f /usr/ccs/lib/cmplrs/cc/libexc.a
-	  then
-	    with_named_thread="-lpthreads -lmach -lc_r"
-	    AC_DEFINE(HAVE_DEC_THREADS, [1])
-            AC_DEFINE([HAVE_DEC_3_2_THREADS], [1],
-                      [Whether we are using OSF1 DEC threads on 3.2])
-            with_osf32_threads="yes"
-            MYSQLD_DEFAULT_SWITCHES="--skip-thread-priority"
+      AC_DEFINE(HAVE_DEC_THREADS, [1], [Whether we are using DEC threads])
       AC_MSG_RESULT("yes")
     else
       AC_MSG_RESULT("no")
-          fi
-	fi
-     fi
-   fi
-fi
+    fi  # DEC threads
+fi  # "$with_named_thread" = "no" -a "$with_mit_threads" = "no"
 
 
 dnl This is needed because -lsocket has to come after the thread