[PATCH 1/1] gdb: Print linker namespace when showing a frame

[Guinevere Larsen <guinevere@redhat.com>]

When a user is stopped in a private linker namespace, the only way for
them to realize that is using the _linker_namespace convenience
variable. While serviceable, this is a sub-optimal solution, as most
users are unaware of convenience variables.

This commit introduces a new way for users to be informed of the linker
namespace of a function, by printing it along with the function name.
This is done by using the proposed syntax for symbols and locations,
like so:

  #0  [[0]]::main ()

This is done by exporting part of the functionality behind the
_linker_namespace variable, namely, find the linker namespace that
contains the given address on the current program space. Since this
change also touched the convenience variable code, this commit fixes a
formatting error in that function.

The namespace ID is only printed if multiple namespaces are active,
otherwise no change in behavior is expected. This commit also updates
the test gdb.base/dlmopen-ns-ids.exp to test this functionality.
---
 gdb/solib.c                               | 28 ++++++++++++++---------
 gdb/solib.h                               |  5 ++++
 gdb/stack.c                               | 13 +++++++++++
 gdb/testsuite/gdb.base/dlmopen-ns-ids.exp | 12 +++++++++-
 gdb/testsuite/gdb.mi/mi-dlmopen.exp       |  2 +-
 5 files changed, 47 insertions(+), 13 deletions(-)

diff --git a/gdb/solib.c b/gdb/solib.c
index 3ec2032f012..2f32f08b645 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -1805,6 +1805,21 @@ remove_user_added_objfile (struct objfile *objfile)
     }
 }
 
+/* See solib.h.  */
+
+int
+linker_namespace_contains_addr (CORE_ADDR addr)
+{
+  for (const solib &so : current_program_space->solibs ())
+    if (solib_contains_address_p (so, addr))
+      {
+	if (so.ops ().supports_namespaces ())
+	  return so.ops ().find_solib_ns (so);
+      }
+
+  return 0;
+}
+
 /* Implementation of the linker_namespace convenience variable.
 
    This returns the GDB internal identifier of the linker namespace,
@@ -1813,19 +1828,10 @@ remove_user_added_objfile (struct objfile *objfile)
 
 static value *
 linker_namespace_make_value (gdbarch *gdbarch, internalvar *var,
-				     void *ignore)
+			     void *ignore)
 {
-  int nsid = 0;
   CORE_ADDR curr_pc = get_frame_pc (get_selected_frame ());
-
-  for (const solib &so : current_program_space->solibs ())
-    if (solib_contains_address_p (so, curr_pc))
-      {
-	if (so.ops ().supports_namespaces ())
-	  nsid = so.ops ().find_solib_ns (so);
-
-	break;
-      }
+  int nsid = linker_namespace_contains_addr (curr_pc);
 
   /* If the PC is not in an SO, or the solib_ops doesn't support
      linker namespaces, the inferior is in the default namespace.  */
diff --git a/gdb/solib.h b/gdb/solib.h
index b9465e103bd..213f66c7ae4 100644
--- a/gdb/solib.h
+++ b/gdb/solib.h
@@ -303,6 +303,11 @@ extern const char *solib_name_from_address (struct program_space *, CORE_ADDR);
 
 extern bool solib_contains_address_p (const solib &, CORE_ADDR);
 
+/* Given the address ADDR, return which linker namespace contains
+   this address in the current program space.  */
+
+int linker_namespace_contains_addr (CORE_ADDR addr);
+
 /* Return whether the data starting at VADDR, size SIZE, must be kept
    in a core file for shared libraries loaded before "gcore" is used
    to be handled correctly when the core file is loaded.  This only
diff --git a/gdb/stack.c b/gdb/stack.c
index e6335669531..10078e06766 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -1363,6 +1363,19 @@ print_frame (struct ui_out *uiout,
     annotate_frame_function_name ();
 
     string_file stb;
+
+    /* Print the linker namespace containing the frame, if there
+       are multiple namespaces active.  */
+    LONGEST num_linker_namespaces;
+    get_internalvar_integer (lookup_internalvar ("_active_linker_namespaces"),
+			     &num_linker_namespaces);
+    if (pc_p && num_linker_namespaces > 1)
+      {
+	LONGEST curr_namespace = linker_namespace_contains_addr (pc);
+	std::string s = string_printf ("[[%ld]]::", curr_namespace);
+	gdb_puts (s.c_str (), &stb);
+      }
+
     gdb_puts (funname ? funname.get () : "??", &stb);
     uiout->field_stream ("func", stb, function_name_style.style ());
     uiout->wrap_hint (3);
diff --git a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
index 4d3e8eba2ab..a88ad817dc1 100644
--- a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
+++ b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
@@ -107,6 +107,8 @@ proc test_info_shared {} {
 
 # Run all tests related to the linkage namespaces convenience
 # variables, _active_namespaces and _current_namespaces.
+# Also tests that the namespace ID is only printed at the correct
+# times.
 proc_with_prefix test_conv_vars {} {
     clean_restart $::binfile
 
@@ -124,6 +126,11 @@ proc_with_prefix test_conv_vars {} {
     gdb_test "print \$_linker_namespace" ".* = 0" \
 	"Still in the default namespace"
 
+    # There should be no namespace ID visible, since there's
+    # only one namespace loaded.
+    gdb_test "backtrace" "\#0\\s+main .*" \
+	"No namespace ID in backtrace"
+
     gdb_breakpoint "inc" allow-pending
     gdb_breakpoint [gdb_get_line_number "TAG: first dlclose"]
 
@@ -132,11 +139,14 @@ proc_with_prefix test_conv_vars {} {
 
 	gdb_test "print \$_linker_namespace" ".* = $dl" \
 	    "Verify we're in namespace $dl"
+
+	gdb_test "frame" "\#0\\s+\\\[\\\[$dl\\\]\\\]::inc.*" \
+	    "Namespace ID in the frame"
     }
 
     # Check that we display the namespace of the selected
     # frame, not the lowermost one.
-    gdb_test "up" "\#1.*in main.*"
+    gdb_test "up" "\#1.*in \\\[\\\[0\\\]\\\]::main.*"
     gdb_test "print \$_linker_namespace" ".* = 0" \
 	"print namespace of selected frame"
 
diff --git a/gdb/testsuite/gdb.mi/mi-dlmopen.exp b/gdb/testsuite/gdb.mi/mi-dlmopen.exp
index c0208ebcc51..3070f879d17 100644
--- a/gdb/testsuite/gdb.mi/mi-dlmopen.exp
+++ b/gdb/testsuite/gdb.mi/mi-dlmopen.exp
@@ -146,7 +146,7 @@ proc check_solib_unload_events {} {
 	-disp keep -func main -file ".*$::srcfile" -line $::bp_main
 
     # Run past all the dlopen and dlmopen calls.
-    mi_execute_to "exec-continue" "breakpoint-hit" main "" ".*" $::bp_loaded \
+    mi_execute_to "exec-continue" "breakpoint-hit" {\[\[0\]\]::main} "" ".*" $::bp_loaded \
 	{"" "disp=\"keep\""} "continue until all libraries are loaded"
 
     # Check that the dynamic linker has now been loaded multiple times.
-- 
2.50.1