Re: JIT compiling with LLVM v9.0

On Thu, Feb 1, 2018 at 8:16 PM, Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> On Fri, Feb 2, 2018 at 2:05 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> On 2018-02-01 09:32:17 -0800, Jeff Davis wrote:
>>> On Wed, Jan 31, 2018 at 12:03 AM, Konstantin Knizhnik
>>> <k(dot)knizhnik(at)postgrespro(dot)ru> wrote:
>>> > The same problem takes place with old versions of GCC: I have to upgrade GCC
>>> > to 7.2 to make it possible to compile this code.
>>> > The problem in not in compiler itself, but in libc++ headers.
>>>
>>> How can I get this branch to compile on ubuntu 16.04? I have llvm-5.0
>>> and gcc-5.4 installed. Do I need to compile with clang or gcc? Any
>>> CXXFLAGS required?
>>
>> Just to understand: You're running in the issue with the header being
>> included from within the extern "C" {}? Hm, I've pushed a quick fix for
>> that.
>
> That change wasn't quite enough: to get this building against libc++
> (Clang's native stdlb) I also needed this change to llvmjit.h so that
> <llvm-c/Types.h> wouldn't be included with the wrong linkage (perhaps
> you can find a less ugly way):
>
> +#ifdef __cplusplus
> +}
> +#endif
> #include <llvm-c/Types.h>
> +#ifdef __cplusplus
> +extern "C"
> +{
> +#endif

This did the trick -- thanks. Sitting through 20 minute computer
crashing link times really brings back C++ nightmares -- if anyone
else needs to compile llvm/clang as I did (I'm stuck on 3.2 with my
aging mint box), I strongly encourage you to use the gold linker.

Question: when watching the compilation log, I see quite a few files
being compiled with both O2 and O1, for example:

clang -Wall -Wmissing-prototypes -Wpointer-arith
-Wdeclaration-after-statement -Wendif-labels
-Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
-fwrapv -Wno-unused-command-line-argument -O2 -O1
-Wno-ignored-attributes -Wno-unknown-warning-option
-Wno-ignored-optimization-argument -I../../../../src/include
-D_GNU_SOURCE -I/home/mmoncure/llvm/include -DLLVM_BUILD_GLOBAL_ISEL
-D_GNU_SOURCE -D_DEBUG -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS
-D__STDC_LIMIT_MACROS -flto=thin -emit-llvm -c -o nbtsort.bc
nbtsort.c

Is this intentional? (didn't check standard compilation, it just jumped out).

merlin