[PATCH 3/5] Allow "phony" ui-out tables

[Tom Tromey <tom@tromey.com>]

In the zebra-striping patch, it's convenient to wrap a stack trace in
a ui-out table.  However, using a real table isn't really desirable,
because that would mean printing headers.  So, this patch adds a hack
specifically for stack traces: a phony table, that does not have field
headers at all.
---
 gdb/cli-out.c         |  2 +-
 gdb/cli-out.h         |  8 +++++++-
 gdb/mi/mi-out.c       |  9 ++++++---
 gdb/mi/mi-out.h       |  2 +-
 gdb/python/py-uiout.h |  5 +++--
 gdb/ui-out.c          | 25 ++++++++++++++++++++++---
 gdb/ui-out.h          | 18 +++++++++++++++++-
 7 files changed, 57 insertions(+), 12 deletions(-)

diff --git a/gdb/cli-out.c b/gdb/cli-out.c
index d8ac13ab827..e1501f5c652 100644
--- a/gdb/cli-out.c
+++ b/gdb/cli-out.c
@@ -59,7 +59,7 @@ cli_ui_out::do_table_body ()
 /* Mark end of a table */
 
 void
-cli_ui_out::do_table_end ()
+cli_ui_out::do_table_end (bool phony)
 {
   m_suppress_output = false;
 }
diff --git a/gdb/cli-out.h b/gdb/cli-out.h
index 74307074a7c..ca138e5ad9a 100644
--- a/gdb/cli-out.h
+++ b/gdb/cli-out.h
@@ -44,8 +44,14 @@ class cli_ui_out : public ui_out
 
   virtual void do_table_begin (int nbrofcols, int nr_rows,
 			       const char *tblid) override;
+
+  /* This overload is used for "phony" tables.  */
+  void do_table_begin () override
+  {
+  }
+
   virtual void do_table_body () override;
-  virtual void do_table_end () override;
+  virtual void do_table_end (bool phony) override;
   virtual void do_table_header (int width, ui_align align,
 				const std::string &col_name,
 				const std::string &col_hdr) override;
diff --git a/gdb/mi/mi-out.c b/gdb/mi/mi-out.c
index 41b0ee8cdbd..0d60c2557e7 100644
--- a/gdb/mi/mi-out.c
+++ b/gdb/mi/mi-out.c
@@ -53,10 +53,13 @@ mi_ui_out::do_table_body ()
 /* Mark end of a table.  */
 
 void
-mi_ui_out::do_table_end ()
+mi_ui_out::do_table_end (bool phony)
 {
-  close (ui_out_type_list); /* body */
-  close (ui_out_type_tuple);
+  if (!phony)
+    {
+      close (ui_out_type_list); /* body */
+      close (ui_out_type_tuple);
+    }
 }
 
 /* Specify table header.  */
diff --git a/gdb/mi/mi-out.h b/gdb/mi/mi-out.h
index d1d26718ac4..6dece4d42b8 100644
--- a/gdb/mi/mi-out.h
+++ b/gdb/mi/mi-out.h
@@ -57,7 +57,7 @@ class mi_ui_out : public ui_out
   virtual void do_table_header (int width, ui_align align,
 			     const std::string &col_name,
 			     const std::string &col_hdr) override;
-  virtual void do_table_end () override;
+  virtual void do_table_end (bool phony) override;
 
   virtual void do_begin (ui_out_type type, const char *id) override;
   virtual void do_end (ui_out_type type) override;
diff --git a/gdb/python/py-uiout.h b/gdb/python/py-uiout.h
index 21c068e9077..2bf0c3a7b46 100644
--- a/gdb/python/py-uiout.h
+++ b/gdb/python/py-uiout.h
@@ -73,9 +73,10 @@ class py_ui_out : public ui_out
   }
   void do_table_body () override
   { }
-  void do_table_end () override
+  void do_table_end (bool phony) override
   {
-    do_end (ui_out_type_list);
+    if (!phony)
+      do_end (ui_out_type_list);
   }
   void do_table_header (int width, ui_align align,
 			const std::string &col_name,
diff --git a/gdb/ui-out.c b/gdb/ui-out.c
index ac792b43905..1c8ceaa90ee 100644
--- a/gdb/ui-out.c
+++ b/gdb/ui-out.c
@@ -184,6 +184,12 @@ class ui_out_table
 
   int entry_level () const;
 
+  /* True if this is a "phony" table.  */
+  bool phony () const
+  {
+    return m_nr_cols == 0;
+  }
+
  private:
 
   state m_state;
@@ -356,9 +362,20 @@ previous table_end."));
 
   m_table_up = std::make_unique<ui_out_table> (level () + 1, nr_cols, tblid);
 
+  gdb_assert (!m_table_up->phony ());
   do_table_begin (nr_cols, nr_rows, tblid.c_str ());
 }
 
+/* See ui-out.h.  */
+
+void
+ui_out::table_begin ()
+{
+  gdb_assert (m_table_up == nullptr);
+  m_table_up = std::make_unique<ui_out_table> (level () + 1, 0, "");
+  do_table_begin ();
+}
+
 void
 ui_out::table_header (int width, ui_align alignment,
 		      const std::string &col_name, const std::string &col_hdr)
@@ -369,7 +386,8 @@ after a table_begin and before a table_body."));
 
   m_table_up->append_header (width, alignment, col_name, col_hdr);
 
-  do_table_header (width, alignment, col_name, col_hdr);
+  if (!m_table_up->phony ())
+    do_table_header (width, alignment, col_name, col_hdr);
 }
 
 void
@@ -381,7 +399,8 @@ ui_out::table_body ()
 
   m_table_up->start_body ();
 
-  do_table_body ();
+  if (!m_table_up->phony ())
+    do_table_body ();
 }
 
 void
@@ -390,7 +409,7 @@ ui_out::table_end ()
   if (m_table_up == nullptr)
     internal_error (_("misplaced table_end or missing table_begin."));
 
-  do_table_end ();
+  do_table_end (m_table_up->phony ());
 
   m_table_up = nullptr;
 }
diff --git a/gdb/ui-out.h b/gdb/ui-out.h
index a7230846115..12da0084332 100644
--- a/gdb/ui-out.h
+++ b/gdb/ui-out.h
@@ -341,8 +341,14 @@ class ui_out
 
   virtual void do_table_begin (int nbrofcols, int nr_rows, const char *tblid)
     = 0;
+
+  /* This is only used for phony tables.  */
+  virtual void do_table_begin ()
+  {
+  }
+
   virtual void do_table_body () = 0;
-  virtual void do_table_end () = 0;
+  virtual void do_table_end (bool phony) = 0;
   virtual void do_table_header (int width, ui_align align,
 				const std::string &col_name,
 				const std::string &col_hdr) = 0;
@@ -396,6 +402,8 @@ class ui_out
   /* A table can only be started or ended by ui_out_emit_table.  */
   friend class ui_out_emit_table;
   void table_begin (int nr_cols, int nr_rows, const std::string &tblid);
+  /* This overload is only used for phony tables.  */
+  void table_begin ();
   void table_end ();
 
   /* A helper for vmessage that wraps a call to do_message.  This will
@@ -460,6 +468,14 @@ class ui_out_emit_table
     m_uiout->table_begin (nr_cols, nr_rows, tblid);
   }
 
+  /* This constructor creates a "phony" table -- this is a hack
+     intended for use just by the stack-generation code.  */
+  explicit ui_out_emit_table (ui_out *uiout)
+    : m_uiout (uiout)
+  {
+    m_uiout->table_begin ();
+  }
+
   ~ui_out_emit_table ()
   {
     m_uiout->table_end ();

-- 
2.49.0