[cfe-commits] r161440 - in /cfe/trunk: include/clang/Basic/DiagnosticSemaKinds.td test/Analysis/cstring-syntax.c

[Matt Beaumont-Gay]

On Wed, Aug 8, 2012 at 10:34 AM, Anna Zaks <ganna at apple.com> wrote:
>
> On Aug 7, 2012, at 12:01 PM, Matt Beaumont-Gay wrote:
>
>> Should we have similar treatment for strncpy?
>>
>> Also, a nit:
>> void f(char* s, char* d) {
>>  strncat(d, s, sizeof(d));
>> }
>>
>> test.cc:5:17: warning: the value of the size argument in 'strncat' is
>> too large, might lead to a buffer overflow [-Wstrncat-size]
>>  strncat(d, s, sizeof(d));
>>                ^~~~~~~~~
>>
>> Here, sizeof(d) is not necessarily too large, just wrong.
>
> It is too large in this case - it should be at least 1 less than sizeof(d), even if d is empty.

My point is that d is a pointer here, not an array.

>
> Anna.
>>
>> On Tue, Aug 7, 2012 at 11:36 AM, Anna Zaks <ganna at apple.com> wrote:
>>> Author: zaks
>>> Date: Tue Aug  7 13:36:58 2012
>>> New Revision: 161440
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=161440&view=rev
>>> Log:
>>> Turn on strncat-size warning implemented a while ago.
>>>
>>> Warns on anti-patterns/typos in the 'size' argument to strncat. The
>>> correct size argument should look like the following:
>>> - strncat(dst, src, sizeof(dst) - strlen(dest) - 1);
>>>
>>> We warn on:
>>> - sizeof(dst)
>>> - sizeof(src)
>>> - sizeof(dst) - strlen(dst)
>>> - sizeof(src) - anything
>>>
>>> (This has been implemented in void Sema::CheckStrncatArguments().)
>>>
>>> Modified:
>>>    cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>>    cfe/trunk/test/Analysis/cstring-syntax.c
>>>
>>> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=161440&r1=161439&r2=161440&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>>> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Tue Aug  7 13:36:58 2012
>>> @@ -373,9 +373,9 @@
>>>
>>> def warn_strncat_large_size : Warning<
>>>   "the value of the size argument in 'strncat' is too large, might lead to a "
>>> -  "buffer overflow">, InGroup<StrncatSize>, DefaultIgnore;
>>> +  "buffer overflow">, InGroup<StrncatSize>, DefaultWarnNoWerror;
>>> def warn_strncat_src_size : Warning<"size argument in 'strncat' call appears "
>>> -  "to be size of the source">, InGroup<StrncatSize>, DefaultIgnore;
>>> +  "to be size of the source">, InGroup<StrncatSize>, DefaultWarnNoWerror;
>>> def note_strncat_wrong_size : Note<
>>>   "change the argument to be the free space in the destination buffer minus "
>>>   "the terminating null byte">;
>>>
>>> Modified: cfe/trunk/test/Analysis/cstring-syntax.c
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/cstring-syntax.c?rev=161440&r1=161439&r2=161440&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/test/Analysis/cstring-syntax.c (original)
>>> +++ cfe/trunk/test/Analysis/cstring-syntax.c Tue Aug  7 13:36:58 2012
>>> @@ -1,4 +1,4 @@
>>> -// RUN: %clang_cc1 -analyze -analyzer-checker=unix.cstring.BadSizeArg -analyzer-store=region -Wno-strlcpy-strlcat-size -Wno-sizeof-array-argument -Wno-sizeof-pointer-memaccess -verify %s
>>> +// RUN: %clang_cc1 -analyze -analyzer-checker=unix.cstring.BadSizeArg -analyzer-store=region -Wno-strncat-size -Wno-strlcpy-strlcat-size -Wno-sizeof-array-argument -Wno-sizeof-pointer-memaccess -verify %s
>>>
>>> typedef __SIZE_TYPE__ size_t;
>>> char  *strncat(char *, const char *, size_t);
>>>
>>>
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>