[cfe-commits] unix.Malloc static checker improvement: memory.LeakPtrValChanged

[Branden Archer]

Oh, one other thing. I do not know who does the committing when the patch
is approved. Should I prove a patch that has my commit message in it and
username? Would either of you be pushing the change, or would I be pushing
it?

Also, thanks for your comments and discussion on this patch, and for
keeping with it for so long! I appreciate your feedback and the opportunity
to learn some about the static analyzer of clang.

- Branden

On Thu, Jan 31, 2013 at 10:10 PM, Branden Archer <b.m.archer4 at gmail.com>wrote:

> Have you double checked that the tests did not generate the warnings
>> before the patch?
>>
>
> When you mentioned this, I had a moment of doubt. I checked for compiler
> warnings and the 'make test' before I emailed my patches, and all came back
> clean. Just to be sure I updated my source and compiled again, all still
> clean. Did you see something in particular, or just wanted to make sure?
>
>
> +void testPassConstPointerIndirectly() {
>> +  struct HasPtr hp;
>> +  hp.p = fopen("myfile.txt", "w");
>> +  fputc(0, (FILE *)&hp);
>> +  return; // expected-warning {{Opened file is never closed; potential
>> resource leak}}
>> +}
>>
>> Heh. Did you really want this test case? It's not actually valid (&hp is
>> a FILE**, not a FILE*):
>>
>
> I knew the test was not proper code, but it was the only way I could think
> of to pass a structure to a known library function that was known to not
> close a file. I replaced it in the attached patches with passing the HasPtr
> structure to a function that accepts it as a const parameter. I am not sure
> this still tests the same thing (as I do not fully appreciate how the
> analyzer knows that a function will not close the stream. I am hoping that
> if the parameter is passed as a const that it will assume this).
>
> - Branden
>
>
> On Thu, Jan 31, 2013 at 8:26 PM, Jordan Rose <jordan_rose at apple.com>wrote:
>
>>
>> On Jan 31, 2013, at 5:21 , Branden Archer <b.m.archer4 at gmail.com> wrote:
>>
>> Basically, you need to pass a pointer which we are tracking to a function
>>> call indirectly (ex: as a field in a struct..). You should pass it to a
>>> function which is known not to free memory or close stream. Finally, you
>>> leak that resource/pointer.
>>>
>>> Previously, we would have a false negative - no leak would be reported.
>>> Now, we should be catching the leak.
>>>
>>
>> Ah, got you. See the first attached patch for these added cases.
>>
>> - Branden
>>
>>
>> +void testPassConstPointerIndirectly() {
>> +  struct HasPtr hp;
>> +  hp.p = fopen("myfile.txt", "w");
>> +  fputc(0, (FILE *)&hp);
>> +  return; // expected-warning {{Opened file is never closed; potential
>> resource leak}}
>> +}
>>
>> Heh. Did you really want this test case? It's not actually valid (&hp is
>> a FILE**, not a FILE*):
>>
>>
>> A few remaining comments for the MallocChecker patch:
>>
>> +  if (ExplodedNode *N = C.generateSink()) {
>>
>> Please use an early return here.
>>
>>
>> +    int offsetBytes =
>> Offset.getOffset()/C.getASTContext().getCharWidth();
>>
>> *Very* nitpicky, but can you put spaces around the /?
>>
>>
>> +       << ((abs(offsetBytes) > 1) ? "bytes" : "byte")
>>
>> Perfect!
>>
>> Jordan
>>
>
>
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