[llvm-dev] (Thin)LTO llvm build

[Mehdi Amini via llvm-dev]

> On Sep 16, 2016, at 2:18 PM, Carsten Mattner <carstenmattner at gmail.com> wrote:
> 
> On Fri, Sep 16, 2016 at 10:54 PM, Mehdi Amini <mehdi.amini at apple.com> wrote:
> 
>> Can you look for the specific errors in the CMake log and error files?
>> 
>> CMake is very good at not presenting the real issue…
>> Here it is trying to build very simple programs to check features
>> availability. Like:
>> 
>>   #include <strings.h>
>>   int main() { ffs(0); return 0; }
> 
> In CMakeError.log there are errors like:
> 
> CheckIncludeFile.c:1:10: fatal error: 'malloc/malloc.h' file not found
> #include <malloc/malloc.h>
> 
> ...
> 
> CheckIncludeFile.c:1:10: fatal error: 'ndir.h' file not found
> #include <ndir.h>
> 
> ...
> 
> CheckIncludeFile.c:1:10: fatal error: 'sys/ndir.h' file not found
> #include <sys/ndir.h>
> 
> ...
> 
> fatal error: 'intrin.h' file not found
> 
> These seem like tests that are expected to fail.
> 
> ...
> 
> The interesting test
> 
>  int main() { __builtin_ffs(0); return 0; }
> 
> fails like this:
> 
> /usr/bin/ld[...]llvm/bin/../lib/LLVMgold.so:
> cannot open shared object file: No such file[…]


I assume that "/usr/bin/ld[...]llvm/bin” is the path where clang is installed right?
It seems that when you built the stage1 clang, it didn’t find Gold installed, and then didn’t build the plugin.
So you need to go back to the first build (not the ThinLTO one, the one with the system compiler), and make sure that CMake finds gold.


> 
> I have two questions here:
> 
> Is there anything I might have missed when configuring the gcc-built
> llvm install for it to be incomplete in the linker department? I mean,
> the system linker is used (not lld) and that via CC=clang is looking
> for the gold linker plugin, which seems to be missing. Probably
> something got lost in my transition from autoconf to cmake?
> 
> Anything else to pass to cmake so that it, in addition to llvm-ar and
> llvm-ranlib, also used lld? Or isn't that a requirement for building
> with ThinLTO?

No requirement for lld.


— 
Mehdi