Problem compiling v6-04-00-patches

[wiso]

Hello, I am tryting to compile git branch v6-04-00-patches on linux manjaro, gcc 7.3.0. I am not using any special flag, just cmake ../souce. I really have to use that branch, I can’t use a newer one (e.g. no problem compiling v6-12-06)

[ 39%] Built target rootcling_tmp
[ 39%] Generating G__IO.cxx, ../../lib/libRIO.rootmap
In file included from input_line_4:2:
In file included from /usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/../../../../include/c++/7.3.0/stdlib.h:36:
In file included from /usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/../../../../include/c++/7.3.0/cstdlib:77:
/usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/../../../../include/c++/7.3.0/bits/std_abs.h:102:3: error: support for type '__float128' is not yet implemented
  abs(__float128 __x)
  ^
/usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/../../../../include/c++/7.3.0/bits/std_abs.h:102:18: error: support for type '__float128' is not yet implemented
  abs(__float128 __x)
                 ^
Error: Error loading the default header files.
make[2]: *** [io/io/CMakeFiles/G__IO.dir/build.make:91: io/io/G__IO.cxx] Error 1
make[1]: *** [CMakeFiles/Makefile2:15095: io/io/CMakeFiles/G__IO.dir/all] Error 2
make: *** [Makefile:152: all] Error 2

[pcanal]

gcc v7.3 was released long after v6.04 and contains changes that are incompatible …

If you need to use v6.04, you may have to also use an older version of the compiler.

[wiso]

Thank you. Do you know if there is any flag I can use to compile with gcc 7?

[pcanal]

Not really. The error seems to be coming from rootcling which means that it is the embedded version of Clang that is not supporting __float128. You could look in the cstdlib header file to see if their a flag to avoid include the declaration with __float128.

Cheers,
Philippe