[PATCH 1/9] Adapt `info probes' to support printing probes of different types.

["Jose E. Marchesi" <jose dot marchesi at oracle dot com>]

A "probe type" (backend for the probe abstraction implemented in probe.[ch])
can extend the information printed by `info probes' by defining additional
columns.  This means that when `info probes' is used to print all the probes
regardless of their types, some of the columns will be "not applicable" to
some of the probes (like, say, the Semaphore column only makes sense for
SystemTap probes).  This patch makes `info probes' fill these slots with "n/a"
marks (currently it breaks the table) and not include headers for which no
actual probe has been found in the list of defined probes.

gdb:

2014-09-25  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* probe.c (print_ui_out_not_applicables): New function.
        (get_num_probes_with_pops): Likewise.
        (info_probes_for_ops): Do not include column headers for probe
        types for which no probe has been actually found on any object.
        Also invoke `print_ui_out_not_applicables' in order to match the
        column rows with the header when probes of several types are
        listed.
---
 gdb/ChangeLog |   10 +++++++++
 gdb/probe.c   |   63 +++++++++++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 67 insertions(+), 6 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index dbd222d..7cc4f00 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,13 @@
+2014-09-25  Jose E. Marchesi  <jose.marchesi@oracle.com>
+
+	* probe.c (print_ui_out_not_applicables): New function.
+	(get_num_probes_with_pops): Likewise.
+	(info_probes_for_ops): Do not include column headers for probe
+	types for which no probe has been actually found on any object.
+	Also invoke `print_ui_out_not_applicables' in order to match the
+	column rows with the header when probes of several types are
+	listed.
+
 2014-09-25  Pedro Alves  <palves@redhat.com>
 
 	* infrun.c (user_visible_resume_ptid): Don't check
diff --git a/gdb/probe.c b/gdb/probe.c
index 859e6e7..5458372 100644
--- a/gdb/probe.c
+++ b/gdb/probe.c
@@ -411,6 +411,33 @@ gen_ui_out_table_header_info (VEC (bound_probe_s) *probes,
   do_cleanups (c);
 }
 
+/* Helper function to print not-applicable strings for all the extra
+   columns defined in a probe_ops.  */
+
+static void
+print_ui_out_not_applicables (const struct probe_ops *pops)
+{
+  struct cleanup *c;
+  VEC (info_probe_column_s) *headings = NULL;
+  info_probe_column_s *column;
+  int ix;
+  
+  if (pops->gen_info_probes_table_header == NULL)
+    return;
+
+  c = make_cleanup (VEC_cleanup (info_probe_column_s), &headings);
+  pops->gen_info_probes_table_header (&headings);
+  
+  for (ix = 0;
+       VEC_iterate (info_probe_column_s, headings, ix, column);
+       ++ix)
+    {
+      ui_out_field_string (current_uiout, column->field_name, _("n/a"));
+    }
+  
+  do_cleanups (c);
+}
+
 /* Helper function to print extra information about a probe and an objfile
    represented by PROBE.  */
 
@@ -483,6 +510,23 @@ get_number_extra_fields (const struct probe_ops *pops)
   return n;
 }
 
+/* Helper function that returns the number of probes in PROBES having
+   the given POPS.  */
+
+static int
+get_num_probes_with_pops (VEC (bound_probe_s) *probes,
+			  const struct probe_ops *pops)
+{
+  int res = 0;
+  struct bound_probe *probe;
+  int ix;
+
+  for (ix = 0; VEC_iterate (bound_probe_s, probes, ix, probe); ++ix)
+    res += (probe->probe->pops == pops);
+
+  return res;
+}
+
 /* See comment in probe.h.  */
 
 void
@@ -518,6 +562,8 @@ info_probes_for_ops (const char *arg, int from_tty,
 	}
     }
 
+  probes = collect_probes (objname, provider, probe_name, pops);
+  
   if (pops == NULL)
     {
       const struct probe_ops *po;
@@ -530,15 +576,16 @@ info_probes_for_ops (const char *arg, int from_tty,
 
 	 To do that, we iterate over all probe_ops, querying each one about
 	 its extra fields, and incrementing `ui_out_extra_fields' to reflect
-	 that number.  */
+	 that number.  But note that we ignore the probe_ops for which no probes
+         are defined with the given search criteria.  */
 
       for (ix = 0; VEC_iterate (probe_ops_cp, all_probe_ops, ix, po); ++ix)
-	ui_out_extra_fields += get_number_extra_fields (po);
+	if (get_num_probes_with_pops (probes, po))
+	  ui_out_extra_fields += get_number_extra_fields (po);
     }
   else
     ui_out_extra_fields = get_number_extra_fields (pops);
 
-  probes = collect_probes (objname, provider, probe_name, pops);
   make_cleanup (VEC_cleanup (probe_p), &probes);
   make_cleanup_ui_out_table_begin_end (current_uiout,
 				       4 + ui_out_extra_fields,
@@ -572,10 +619,12 @@ info_probes_for_ops (const char *arg, int from_tty,
       const struct probe_ops *po;
       int ix;
 
-      /* We have to generate the table header for each new probe type that we
-	 will print.  */
+      /* We have to generate the table header for each new probe type
+	 that we will print.  Note that this excludes probe types not
+	 having any defined probe with the search criteria.  */
       for (ix = 0; VEC_iterate (probe_ops_cp, all_probe_ops, ix, po); ++ix)
-	gen_ui_out_table_header_info (probes, po);
+	if (get_num_probes_with_pops (probes, po) > 0)
+	  gen_ui_out_table_header_info (probes, po);
     }
   else
     gen_ui_out_table_header_info (probes, pops);
@@ -605,6 +654,8 @@ info_probes_for_ops (const char *arg, int from_tty,
 	       ++ix)
 	    if (probe->probe->pops == po)
 	      print_ui_out_info (probe->probe);
+	    else if (get_num_probes_with_pops (probes, po) > 0)
+	      print_ui_out_not_applicables (po);
 	}
       else
 	print_ui_out_info (probe->probe);
-- 
1.7.10.4