[LLVMdev] [PATCH]: MSVC build enhancements

[José Fonseca]

On Sat, Mar 6, 2010 at 11:27 PM, OvermindDL1 <overminddl1 at gmail.com> wrote:
> To the mailing list this time...
>
> On Sat, Mar 6, 2010 at 4:26 PM, OvermindDL1 <overminddl1 at gmail.com> wrote:
>> On Sat, Mar 6, 2010 at 4:19 PM, José Fonseca <jose.r.fonseca at gmail.com> wrote:
>>>>> --- a/include/llvm/System/DataTypes.h.cmake
>>>>> +++ b/include/llvm/System/DataTypes.h.cmake
>>>>> @@ -100,6 +100,9 @@ typedef u_int64_t uint64_t;
>>>>>  #else
>>>>>  #include <math.h>
>>>>>  #endif
>>>>> +#ifdef HAVE_STDINT_H
>>>>> +#include <stdint.h>
>>>>> +#else /* !HAVE_STDINT_H */
>>>>
>>>> This looks incorrect to me. stdint.h is already included below for
>>>> non-MSVC systems. Maybe you inteded to #include it for MSVC only? Or do
>>>> intend to correct some problem with non-MSVC builds too?
>>>
>>> The idea here is indeed to use an external stdint.h in MSVC builds.
>>>
>>> The problem is that everybody except Microsoft recognized the
>>> usefulness of stdint.h types [1], and they work around it for MSVC by
>>> defining the stdint.h types themselves. LLVM does it. Mesa3D did it
>>> too. But that won't work when two such projects try to interoperate --
>>> you'll get errors that uint8_t/uint16_t/uint32_t/etc has been
>>> redefined.
>>>
>>> There is more than one way to address this. The solution I came up
>>> with was to make all projects respect HAVE_STDINT_H, and only define
>>> the stdint types if HAVE_STDINT_H is not defined. Then all projects
>>> can use the same definition, without symbol clashes. We actually ship
>>> a tiny stdint.h in Mesa3D,
>>> http://cgit.freedesktop.org/mesa/mesa/tree/include/c99/stdint.h , but
>>> there are many free replacements out there.
>>>
>>> This is not a problem specific to Mesa and LLVM -- it is a problem
>>> faced by any pair of projects that use stdint types and want to build
>>> on MSVC.
>>>
>>> Jose
>>>
>>> [1] I'm being unfair. Microsoft certainly recognized by now how useful
>>> the stdint.h types are to write portable code, which is probably the
>>> reason why they haven't been implemented yet. It doesn't appear C99
>>> will be implemented soon either:
>>> https://connect.microsoft.com/VisualStudio/feedback/details/485416/support-c99
>>
>> Boost has such an stdint compatibility header in their TR1 section.
>> Why not take it and put it in LLVM itself, the boost license
>> encourages that use and it interoperates properly with every known
>> compiler, adding the missing things on those compilers if necessary.

You mean https://svn.boost.org/trac/boost/browser/trunk/boost/cstdint.hpp .

Levering their definitions sounds a good idea in general. There are
some tweaks necessary: boost defines only cstdint.hpp, not stdint.h,
and it actually includes system's stdint.h. This won't work with the
LLVM-C bindings.


OK.  It seems my changes are far from trivial. Apologies for naively
assuming they were.

I think it's better not apply any of this for LLVM 2.7. I'll workout
individual patches based on the feedback I got and re-submit at a time
it can receive more testing without fear of breaking stuff.

Jose