OTP-5037 Document debug support.

          Debug trace output for connection activity could be enabled
          setting the trace level as an integer to the EI_TRACELEVEL
          environment variable. This option could also be read and set from
          a running program using ei_get_tracelevel(void) and
          ei_set_tracelevel(int).

3 files changed, 46 insertions, 3 deletions

diff --git a/lib/erl_interface/doc/src/ei_connect.xml b/lib/erl_interface/doc/src/ei_connect.xml
index 08e7b122c6..abf705f9e2 100644
--- a/lib/erl_interface/doc/src/ei_connect.xml
+++ b/lib/erl_interface/doc/src/ei_connect.xml
@@ -619,6 +619,16 @@ typedef struct {
         <p>These are convenience functions for some common name lookup functions.</p>
       </desc>
     </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_get_tracelevel(void)</nametext></name>
+      <name><ret>void</ret><nametext>ei_set_tracelevel(int level)</nametext></name>
+      <fsummary>Get and set functions for tracing.</fsummary>
+      <desc>
+        <p>These functions are used to set tracing on the distribution. The levels are different verbosity levels. A higher level means more information.
+	See also Debug Information and <c><![CDATA[EI_TRACELEVEL]]></c> below. </p>
+	<p> <c><![CDATA[ei_set_tracelevel]]></c> and <c><![CDATA[ei_get_tracelevel]]></c> are not thread safe.  </p>
+      </desc>
+    </func>
   </funcs>
 
   <section>
@@ -634,6 +644,17 @@ typedef struct {
       <item>the environment variable <c><![CDATA[ERL_EPMD_PORT]]></c>
        is set correctly.</item>
     </list>
+    <p>The connection attempt can be traced by setting a tracelevel by either using
+    <c><![CDATA[ei_set_tracelevel]]></c> or by setting the environment variable <c><![CDATA[EI_TRACELEVEL]]></c>.
+    The different tracelevels has the following messages:</p>
+    <list>
+    	<item>1: Verbose error messages</item>
+    	<item>2: Above messages and verbose warning messages </item>
+    	<item>3: Above messages and progress reports for connection handling</item>
+    	<item>4: Above messages and progress reports for communication</item>
+    	<item>5: Above messages and progress reports for data conversion</item>
+    </list>
   </section>
+
 </cref>
 
diff --git a/lib/erl_interface/include/ei.h b/lib/erl_interface/include/ei.h
index 01272244e1..d1a697615a 100644
--- a/lib/erl_interface/include/ei.h
+++ b/lib/erl_interface/include/ei.h
@@ -339,7 +339,13 @@ const char *ei_thisalivename(const ei_cnode* ec);
 
 erlang_pid *ei_self(ei_cnode* ec);
 
+/* 
+ * settings 
+ */
+
 void ei_set_compat_rel(unsigned rel);
+void ei_set_tracelevel(int);
+int ei_get_tracelevel(void);
 
 /* 
  * We have erl_gethost*() so we include ei versions as well.
diff --git a/lib/erl_interface/src/connect/ei_connect.c b/lib/erl_interface/src/connect/ei_connect.c
index 9ac5a93c5a..265e133158 100644
--- a/lib/erl_interface/src/connect/ei_connect.c
+++ b/lib/erl_interface/src/connect/ei_connect.c
@@ -97,7 +97,11 @@
 #include "ei_epmd.h"
 #include "ei_internal.h"
 
+#ifdef _REENTRANT
+
+#else
 int ei_tracelevel = 0;
+#endif
 
 #define COOKIE_FILE "/.erlang.cookie"
 #define EI_MAX_HOME_PATH 1024
@@ -249,8 +253,22 @@ ei_cnode *ei_fd_to_cnode(int fd)
     return &sockinfo->cnode;
 }
 
+
+/***************************************************************************
+ *  Get/Set tracelevel
+ ***************************************************************************/
+
+void ei_set_tracelevel(int level) {
+    ei_tracelevel = level;
+}
+
+int ei_get_tracelevel(void) {
+    return ei_tracelevel;
+}
+
+
 /***************************************************************************
- *  XXXX
+ *  Distversion 
  ***************************************************************************/
 
 int ei_distversion(int fd)
@@ -1282,8 +1300,6 @@ error:
     return -1;
 }
 
-/* FIXME fix the signed/unsigned mess..... */
-
 static int send_name_or_challenge(int fd, char *nodename,
 				  int f_chall,
 				  unsigned challenge,