[LLVMdev] PATCH: AddressSanitizer: Fix errors about mis-matched exception specifiers for intercepted libc functions on Linux

[Kostya Serebryany]

On Mon, Jun 25, 2012 at 2:01 PM, Chandler Carruth <chandlerc at google.com>wrote:

> I really don't see why this is the correct fix.
>
> 1) I like including the system's headers. It ensures that the interceptor
> DTRT.
> 2) It's hardly the only system header you pull in here
>

Oh, it actually is (was) the only system header left in this file. I am
glad to be able to get rid of it.
I've been fighting the system headers for a long time now: for this kind of
code they are surprisingly painful.
Now, we have zero system headers in .h files and just a few in OS-dependent
.cc files.

We are replacing functions that have a very clear "C" interface which is
not going to change, so including system headers does not help.
But it actually hurts very much: event some innocent system headers like
stddef.h or stdlib.h bring along some unexpected typedefs, definds, decls,
etc.
Things get worse if a .cc file is used on more than one platform (e.g.
asan_malloc_linux.cc
is also used on Android) where the system headers are different.



> 3) I think we should probably match what glibc does when declaring these
> routines. any reason to avoid this?
>

We only need to keep the functions binary-compatible.


--kcc


>
> On Mon, Jun 25, 2012 at 3:00 AM, Kostya Serebryany <kcc at google.com> wrote:
>
>> done: r159132.
>>
>>
>> On Mon, Jun 25, 2012 at 1:47 PM, Kostya Serebryany <kcc at google.com>wrote:
>>
>>> .. And the right fix would be to completely get rid of "#include
>>> <malloc.h>" in this file.
>>> I'll do that change.
>>>
>>> --kcc
>>>
>>>
>>> On Mon, Jun 25, 2012 at 1:42 PM, Alexander Potapenko <glider at google.com>wrote:
>>>
>>>> On Mon, Jun 25, 2012 at 1:10 PM, Chandler Carruth <chandlerc at google.com>
>>>> wrote:
>>>> > Hello,
>>>> >
>>>> > On modern Linux installs, glibc has a very annoying practice: it adds
>>>> an
>>>> > empty exception specifier to lots of libc functions as an
>>>> optimization. It
>>>> > only does this if the compiler is modern and GCC-like, and we are
>>>> compiling
>>>> > in C++ mode.
>>>> >
>>>> > This, however, causes GCC to complain about signature mismatches
>>>> between the
>>>> > glibc functions declared in malloc.h and those defined as an alias in
>>>> the
>>>> > interceptors library:
>>>> >
>>>> > ..../asan_malloc_linux.cc:57:1: error: declaration of 'void
>>>> free(void*)' has
>>>> > a different exception specifier
>>>> > /usr/include/malloc.h:66:13: error: from previous declaration 'void
>>>> > free(void*) throw ()'
>>>> Looking at /usr/include/malloc.h I don't see any instances of throw()
>>>> (Goobuntu Lucid)
>>>> Shouldn't we have the same set of standard headers?
>>>> _______________________________________________
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>>>>
>>>
>>>
>>
>
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