gdb: add convenience variables around linker namespace debugging

This commit adds 2 simple built-in convenience variables to help users
debug an inferior with multiple linker namespaces. The first is
$_active_linker_namespaces, which just counts how many namespaces have SOs
loaded onto them. The second is $_current_linker_namespace, and it tracks
which namespace the current location in the inferior belongs to.

This commit also introduces a test ensuring that we track namespaces
correctly, and that a user can use the $_current_linker_namespace
variable to set a conditional breakpoint, while linespec changes aren't
finalized to make it more convenient.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-by: Kevin Buettner <kevinb@redhat.com>

3 files changed, 63 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/default.exp b/gdb/testsuite/gdb.base/default.exp
index d4d6b20..3abd049 100644
--- a/gdb/testsuite/gdb.base/default.exp
+++ b/gdb/testsuite/gdb.base/default.exp
@@ -699,6 +699,8 @@ set show_conv_list \
 	{$_gdb_minor = 1} \
 	{$_shell_exitsignal = void} \
 	{$_shell_exitcode = 0} \
+	{$_active_linker_namespaces = 1} \
+	{$_current_linker_namespace = <error: No registers.>}\
     }
 if [allow_python_tests] {
     append show_conv_list \
diff --git a/gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c b/gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c
index 3bcd819..c7c038a 100644
--- a/gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c
+++ b/gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c
@@ -41,6 +41,12 @@ main (void)
   handle[2] = dlmopen (LM_ID_NEWLM, DSO_NAME, RTLD_LAZY | RTLD_LOCAL);
   assert (handle[2] != NULL);
 
+  for (dl = 2; dl >= 0; dl--)
+    {
+      fun = dlsym (handle[dl], "inc");
+      fun (dl);
+    }
+
   dlclose (handle[0]); /* TAG: first dlclose */
   dlclose (handle[1]); /* TAG: second dlclose */
   dlclose (handle[2]); /* TAG: third dlclose */
diff --git a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
index 3ddc07e..1af57d1 100644
--- a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
+++ b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
@@ -105,4 +105,59 @@ proc test_info_shared {} {
 	"after unloading everything"
 }
 
+# Run all tests related to the linkage namespaces convenience
+# variables, _active_namespaces and _current_namespaces.
+proc_with_prefix test_conv_vars {} {
+    clean_restart $::binfile
+
+    gdb_test "print \$_active_linker_namespaces" "1" \
+	"1 namespace before starting inferior"
+    gdb_test "print \$_current_linker_namespace" "No registers." \
+	"No current namespace before starting inferior"
+
+    if { ![runto_main] } {
+	return
+    }
+
+    gdb_test "print \$_active_linker_namespaces" "1" \
+	"Before activating namespaces"
+    gdb_test "print \$_current_linker_namespace" ".*\"\\\[\\\[0\\\]\\\]\"" \
+	"Still in the default namespace"
+
+    gdb_breakpoint "inc" allow-pending
+    gdb_breakpoint [gdb_get_line_number "TAG: first dlclose"]
+
+    foreach_with_prefix dl {3 2 1} {
+	gdb_continue_to_breakpoint "inc"
+
+	gdb_test "print \$_current_linker_namespace" ".*\"\\\[\\\[$dl\\\]\\\]\"" \
+	    "Verify we're in namespace $dl"
+    }
+
+    gdb_continue_to_breakpoint "first dlclose"
+    gdb_test "print \$_active_linker_namespaces" "4" "all SOs loaded"
+
+    gdb_test "next" ".*second dlclose.*" "close one SO"
+    gdb_test "print \$_active_linker_namespaces" "3" "one SOs unloaded"
+    gdb_test "next" ".*third dlclose.*" "close another SO"
+    gdb_test "print \$_active_linker_namespaces" "2" "two SOs unloaded"
+
+    # Restarting GDB so that we can test setting a breakpoint
+    # using the convenience variable, while a proper bp syntax
+    # isn't implemented for namespaces
+    clean_restart $::binfile
+    if {![runto_main]} {
+	return
+    }
+
+    # We need to load one SO because you can't have confitional
+    # breakpoints and pending breakpoints at the same time with
+    # gdb_breakpoint.
+    gdb_test "next" ".*assert.*" "load the first SO"
+    gdb_breakpoint "inc if \$_streq(\$_current_linker_namespace, \"\[\[2\]\]\")"
+    gdb_continue_to_breakpoint "inc"
+    gdb_continue_to_end "" continue 1
+}
+
 test_info_shared
+test_conv_vars