Re: [PATCH] python: Fix memleak in do_start_initialization

[Simon Marchi <simon.marchi@polymtl.ca>]

On 2017-11-26 04:54 PM, Tom Tromey wrote:
>>>>>> "Simon" == Simon Marchi <simon.marchi@polymtl.ca> writes:
> 
> Simon> There's already a comment in that regard:
> 
> Hah, I totally missed this.
> 
> Simon> When I read it, I thought it referred only to progname_copy, but it
> Simon> also applies to progname for Python 2.  I integrated your suggestion,
> Simon> wdyt?
> 
> Simon> -  char *progname;
> Simon> +  gdb::unique_xmalloc_ptr<char> progname;
> 
> I think the patch looks good, but would be even clearer if this
> declaration were moved into the #if, so that..
> 
> Simon> -  progname = concat (ldirname (python_libdir).c_str (), SLASH_STRING, "bin",
> Simon> -		     SLASH_STRING, "python", (char *) NULL);
> Simon> +  progname.reset (concat (ldirname (python_libdir).c_str (), SLASH_STRING,
> Simon> +			  "bin", SLASH_STRING, "python", (char *) NULL));
> 
> ...this reset could be replaced with plain initialization.
> 
> thanks,
> Tom
> 

Good idea, here's what I pushed.  Thanks for the comments!


From e8e7d10c39955e7ff99ff42f6f16d6befe2fa12e Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@polymtl.ca>
Date: Sun, 26 Nov 2017 19:32:47 -0500
Subject: [PATCH] python: Fix memleak in do_start_initialization

While playing with valgrind, I noticed that with Python 3, the progname
variable in do_start_initialization is not being freed (concat returns a
malloc'ed string).  This patch uses unique_xmalloc_ptr to manage it.
With Python 2, we pass progname it directly to Py_SetProgramName, so it
should not be freed.  We therefore release it before passing it.

gdb/ChangeLog:

	* python/python.c (do_start_initialization): Change progname
	type to gdb::unique_xmalloc_ptr.  Release the pointer when using
	Python 2.
---
 gdb/ChangeLog       |  6 ++++++
 gdb/python/python.c | 12 ++++++------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a901409228..b3032ed7d8 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2017-11-26  Simon Marchi  <simon.marchi@polymtl.ca>
+
+	* python/python.c (do_start_initialization): Change progname
+	type to gdb::unique_xmalloc_ptr.  Release the pointer when using
+	Python 2.
+
 2017-11-26  Tom Tromey  <tom@tromey.com>

 	* common/format.h: Add include guards.
diff --git a/gdb/python/python.c b/gdb/python/python.c
index 5f152611e8..9ed9b6b1ca 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -1658,7 +1658,6 @@ finalize_python (void *ignore)
 static bool
 do_start_initialization ()
 {
-  char *progname;
 #ifdef IS_PY3K
   int i;
   size_t progsize, count;
@@ -1672,19 +1671,20 @@ do_start_initialization ()
      /foo/bin/python
      /foo/lib/pythonX.Y/...
      This must be done before calling Py_Initialize.  */
-  progname = concat (ldirname (python_libdir).c_str (), SLASH_STRING, "bin",
-		     SLASH_STRING, "python", (char *) NULL);
+  gdb::unique_xmalloc_ptr<char> progname
+    (concat (ldirname (python_libdir).c_str (), SLASH_STRING, "bin",
+	      SLASH_STRING, "python", (char *) NULL));
 #ifdef IS_PY3K
   std::string oldloc = setlocale (LC_ALL, NULL);
   setlocale (LC_ALL, "");
-  progsize = strlen (progname);
+  progsize = strlen (progname.get ());
   progname_copy = (wchar_t *) PyMem_Malloc ((progsize + 1) * sizeof (wchar_t));
   if (!progname_copy)
     {
       fprintf (stderr, "out of memory\n");
       return false;
     }
-  count = mbstowcs (progname_copy, progname, progsize + 1);
+  count = mbstowcs (progname_copy, progname.get (), progsize + 1);
   if (count == (size_t) -1)
     {
       fprintf (stderr, "Could not convert python path to string\n");
@@ -1697,7 +1697,7 @@ do_start_initialization ()
      it is not freed after this call.  */
   Py_SetProgramName (progname_copy);
 #else
-  Py_SetProgramName (progname);
+  Py_SetProgramName (progname.release ());
 #endif
 #endif

-- 
2.15.0