[binutils-gdb] fix leak in gdb_environ

[Philippe Waroquiers <philippe@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=c801f8f138c03cde994db597d11953c21ed892de

commit c801f8f138c03cde994db597d11953c21ed892de
Author: Philippe Waroquiers <philippe.waroquiers@skynet.be>
Date:   Sun Nov 27 19:20:58 2022 +0100

    fix leak in gdb_environ
    
    valgrind reports a leak when assigning a gdb_environ to another gdb_environ.
    The memory allocated for the target gdb_environ env variables is not released.
    The gdb_environ selftest reproduces the leak (see below).
    Fix the leak by clearing the target gdb_environ before std::move-ing the
    members.
    
    Tested natively and re-running all tests under valgrind.
    
    ==3261873== 4,842 bytes in 69 blocks are definitely lost in loss record 6,772 of 6,839
    ==3261873==    at 0x483979B: malloc (vg_replace_malloc.c:393)
    ==3261873==    by 0x25A454: xmalloc (alloc.c:57)
    ==3261873==    by 0x7D1E4E: xstrdup (xstrdup.c:34)
    ==3261873==    by 0x7E2A51: gdb_environ::from_host_environ() (environ.cc:56)
    ==3261873==    by 0x66F1C8: test_reinit_from_host_environ (environ-selftests.c:78)
    ==3261873==    by 0x66F1C8: selftests::gdb_environ_tests::run_tests() (environ-selftests.c:285)
    ==3261873==    by 0x7EFC43: operator() (std_function.h:622)
    =
    
    Approved-By: Simon Marchi <simon.marchi@efficios.com>

Diff:
---
 gdbsupport/environ.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/gdbsupport/environ.cc b/gdbsupport/environ.cc
index f5f6b38e19c..2d8e3ea6e92 100644
--- a/gdbsupport/environ.cc
+++ b/gdbsupport/environ.cc
@@ -29,6 +29,8 @@ gdb_environ::operator= (gdb_environ &&e)
   if (&e == this)
     return *this;
 
+  this->clear ();
+
   m_environ_vector = std::move (e.m_environ_vector);
   m_user_set_env = std::move (e.m_user_set_env);
   m_user_unset_env = std::move (e.m_user_unset_env);