[patch] Python Pretty Printers get disabled on libstdc++ reload by GDB (PR libstdc++/68448)

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68448
https://bugzilla.redhat.com/show_bug.cgi?id=1279406

echo -e '#include <vector>\nint main(){std::vector<int> l;\nreturn 0;}'|g++ -g -Wall -x c++ -;gdb -q ./a.out -batch -ex 'b 3' -ex r -ex 'p l' -ex r -ex 'p l'

Actual:
[...]
$1 = std::vector of length 0, capacity 0
[...]
$2 = {<std::_Vector_base<int, std::allocator<int> >> = {_M_impl = {<std::allocator<int>> = {<__gnu_cxx::new_allocator<int>> = {<No data fields>}, <No data fields>}, _M_start = 0x0, _M_finish = 0x0, _M_end_of_storage = 0x0}}, <No data fields>}

Expected:
[...]
$1 = std::vector of length 0, capacity 0
[...]
$2 = std::vector of length 0, capacity 0


Thanks,
Jan

	* python/hook.in: Call register_libstdcxx_printers.
	* python/libstdcxx/v6/__init__.py: Wrap it to
	register_libstdcxx_printers.

diff --git a/libstdc++-v3/python/hook.in b/libstdc++-v3/python/hook.in
index 07fe4c6..703b6a7 100644
--- a/libstdc++-v3/python/hook.in
+++ b/libstdc++-v3/python/hook.in
@@ -55,4 +55,7 @@ if gdb.current_objfile () is not None:
     if not dir_ in sys.path:
         sys.path.insert(0, dir_)
 
-import libstdcxx.v6
+# Call a function as a plain import would not execute body of the included file
+# on repeated reloads of this object file.
+from libstdcxx.v6 import register_libstdcxx_printers
+register_libstdcxx_printers(gdb.current_objfile())
diff --git a/libstdc++-v3/python/libstdcxx/v6/__init__.py b/libstdc++-v3/python/libstdcxx/v6/__init__.py
index de3aa72..d8e060c 100644
--- a/libstdc++-v3/python/libstdcxx/v6/__init__.py
+++ b/libstdc++-v3/python/libstdcxx/v6/__init__.py
@@ -15,10 +15,6 @@
 
 import gdb
 
-# Load the pretty-printers.
-from .printers import register_libstdcxx_printers
-register_libstdcxx_printers(gdb.current_objfile())
-
 # Load the xmethods if GDB supports them.
 def gdb_has_xmethods():
     try:
@@ -27,6 +23,11 @@ def gdb_has_xmethods():
     except ImportError:
         return False
 
-if gdb_has_xmethods():
-    from .xmethods import register_libstdcxx_xmethods
-    register_libstdcxx_xmethods(gdb.current_objfile())
+def register_libstdcxx_printers(obj):
+    # Load the pretty-printers.
+    from .printers import register_libstdcxx_printers
+    register_libstdcxx_printers(obj)
+
+    if gdb_has_xmethods():
+        from .xmethods import register_libstdcxx_xmethods
+        register_libstdcxx_xmethods(obj)