python: Fix memleak in do_start_initialization
Commit Message
On 2017-11-26 02:00 PM, Tom Tromey wrote:
>>>>>> "Simon" == Simon Marchi <simon.marchi@polymtl.ca> writes:
>
> Simon> While playing with valgrind, I noticed that the progname variable in
> Simon> do_start_initialization is not being freed (concat returns a malloc'ed
> Simon> string). Use a unique_xmalloc_ptr to manage it.
>
> I don't think this is quite correct.
> On the Python 2 branch, the code does this:
>
> Py_SetProgramName (progname);
>
> The docs for Py_SetProgramName say:
>
> The argument should point to a
> zero-terminated character string in static storage whose contents
> will not change for the duration of the program's execution.
Ahh, you are completely right, I always forget about Python 2. And I relied
too much on my IDE to find usages of progname, it didn't find the usage in the
disabled #if branch. At least it would have failed at compile time with
Python 2, not runtime.
> I think a comment referring to the Python docs would be better.
> And, freeing progname on the Python 3 branch is ok.
> Maybe the Python 2 branch could pass "progname.release ()".
There's already a comment in that regard:
/* Note that Py_SetProgramName expects the string it is passed to
remain alive for the duration of the program's execution, so
it is not freed after this call. */
When I read it, I thought it referred only to progname_copy, but it
also applies to progname for Python 2. I integrated your suggestion,
wdyt?
From 468fe44d21dfed10f547d790d233547ab0da2cf5 Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@polymtl.ca>
Date: Sat, 25 Nov 2017 22:51:02 -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/python/python.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
Comments
>>>>> "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
@@ -1658,7 +1658,7 @@ finalize_python (void *ignore)
static bool
do_start_initialization ()
{
- char *progname;
+ gdb::unique_xmalloc_ptr<char> progname;
#ifdef IS_PY3K
int i;
size_t progsize, count;
@@ -1672,19 +1672,19 @@ 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);
+ progname.reset (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