Re: [Qemu-trivial] [PATCH] Changed malloc() to g_malloc() at places where return value was not being checked

[haris iqbal]

On Tue, Mar 22, 2016 at 9:35 PM, Paolo Bonzini <address@hidden> wrote:
>
>
> On 22/03/2016 16:52, haris iqbal wrote:
>> On Tue, Mar 22, 2016 at 8:27 PM, Peter Maydell <address@hidden> wrote:
>>> On 22 March 2016 at 14:33, Md Haris Iqbal <address@hidden> wrote:
>>>> Signed-off-by: Md Haris Iqbal <address@hidden>
>>>
>>> Hi. I'm afraid you can't just change malloc() calls to
>>> g_malloc() without also changing the corresponding free()
>>> calls to g_free().
>>
>> Ok, I will do that.
>>
>>>
>>> Also, at least the thunk.c code has had patches and
>>> discussion on-list regarding its malloc() calls. It's
>>> often worth searching the mailing list to check you won't
>>> be repeating work that somebody else is already doing.
>>>
>>>> ---
>>>>  bsd-user/elfload.c | 2 +-
>>>>  bsd-user/qemu.h    | 2 +-
>>>>  linux-user/qemu.h  | 2 +-
>>>>  thunk.c            | 2 +-
>>>>  ui/shader.c        | 2 +-
>>>>  5 files changed, 5 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/bsd-user/elfload.c b/bsd-user/elfload.c
>>>> index 0a6092b..40bd1f2 100644
>>>> --- a/bsd-user/elfload.c
>>>> +++ b/bsd-user/elfload.c
>>>> @@ -1064,7 +1064,7 @@ static void load_symbols(struct elfhdr *hdr, int fd)
>>>>
>>>>   found:
>>>>      /* Now know where the strtab and symtab are.  Snarf them. */
>>>> -    s = malloc(sizeof(*s));
>>>> +    s = g_malloc(sizeof(*s));
>>>>      syms = malloc(symtab.sh_size);
>>>>      if (!syms) {
>>>>          free(s);
>>
>> I did that because the other one has a return value check. Which (as
>> discussed with Paolo Bonzini) should be done in a seperate patch.
>
> In this case you can convert syms to g_try_malloc.

Great. I will do that.

>
> Paolo
>
>>>
>>> It's very odd to have only part of this data structure be
>>> malloc and part g_malloc. We should convert all of it
>>> or none of it.
>>>
>>>> diff --git a/ui/shader.c b/ui/shader.c
>>>> index 9264009..43c6f64 100644
>>>> --- a/ui/shader.c
>>>> +++ b/ui/shader.c
>>>> @@ -83,7 +83,7 @@ GLuint qemu_gl_create_compile_shader(GLenum type, const 
>>>> GLchar *src)
>>>>      glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
>>>>      if (!status) {
>>>>          glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &length);
>>>> -        errmsg = malloc(length);
>>>> +        errmsg = g_malloc(length);
>>>>          glGetShaderInfoLog(shader, length, &length, errmsg);
>>>>          fprintf(stderr, "%s: compile %s error\n%s\n", __func__,
>>>>                  (type == GL_VERTEX_SHADER) ? "vertex" : "fragment",
>>>
>>> Changes to the ui/shader.c code should be in a different
>>> patch, since they're not related to the linux-user or
>>> bsd-user code. (Splitting out bsd-user changes would
>>> also be a good idea.) The idea here is that different
>>> areas of the code have different maintainers, and so
>>> review is by different people (and a problem in one part
>>> of a patch doesn't then hold up an unrelated good change
>>> in a different part).
>>
>> Ya, sure. I will split up the patches for different files and send
>> them. I can cc the seperate maintainer also then.
>>
>>>
>>> thanks
>>> -- PMM
>>
>>
>>


One more question. About tracking down g_free(). I thought of
submitting for linux-user/qemu.h first. As it is done in a function
called lock_user(), which is called by many other functions (around
144, too many to be checked manually). The interesting part is, the
free is done by a pair function called unlock_user(). I just want to
ask if all those lock_user() calls has a matching unlock_user() call
to free() the malloc(), or there is a hidden free somewhere else also?
This would save a lot of time. Thanks.

(PS. I saw in the MAINTAINER file that address@hidden should be
queried for questions regarding linux-* files. So mailing here.)


-- 

With regards,

Md Haris Iqbal,
Placement Coordinator, MTech IT
NITK Surathkal,
Contact: +91 8861996962