[BZ,#20314] Make copies of cstdlib/cmath and use them

  If C++ headers <cstdlib> or <cmath> are used, GCC 6 will include
/usr/include/stdlib.h or /usr/include/math.h from "#include_next"
(instead of stdlib/stdlib.h or math/math.h in the glibc source
directory), and this turns up as a make dependency.  An implicit
rule will kick in and make will try to install stdlib/stdlib.h or
math/math.h as /usr/include/stdlib.h or /usr/include/math.h because
the target is out of date.  We make a copy of <cstdlib> and <cmath>
in the glibc build directory so that stdlib/stdlib.h and math/math.h
will be used instead of /usr/include/stdlib.h and /usr/include/math.h.

OK for master?

H.J.
---
	[BZ #20314]
	* Makeconfig (CXXFLAGS): Prepend -I$(common-objpfx).
	* Makerules (before-compile): Add $(common-objpfx)cstdlib and
	$(common-objpfx)cmath.
	($(common-objpfx)cstdlib): New target.
	($(common-objpfx)cmath): Likewise.
---
 Makeconfig |  3 ++-
 Makerules  | 24 ++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)
  

see this thread:
https://sourceware.org/ml/libc-alpha/2016-06/msg00246.html
-mike
  

On Sun, Jul 3, 2016 at 11:45 PM, Mike Frysinger <vapier@gentoo.org> wrote:
> see this thread:
> https://sourceware.org/ml/libc-alpha/2016-06/msg00246.html
> -mike

It doesn't fix "make xcheck" nor I think <stdlib.h> should be included
first for any C++ tests.
  

On 06/30/2016 12:57 PM, H.J. Lu wrote:
> If C++ headers <cstdlib> or <cmath> are used, GCC 6 will include
> /usr/include/stdlib.h or /usr/include/math.h from "#include_next"
> (instead of stdlib/stdlib.h or math/math.h in the glibc source
> directory), and this turns up as a make dependency.  An implicit
> rule will kick in and make will try to install stdlib/stdlib.h or
> math/math.h as /usr/include/stdlib.h or /usr/include/math.h because
> the target is out of date.  We make a copy of <cstdlib> and <cmath>
> in the glibc build directory so that stdlib/stdlib.h and math/math.h
> will be used instead of /usr/include/stdlib.h and /usr/include/math.h.
> 
> OK for master?
> 
> H.J.
> ---
> 	[BZ #20314]
> 	* Makeconfig (CXXFLAGS): Prepend -I$(common-objpfx).
> 	* Makerules (before-compile): Add $(common-objpfx)cstdlib and
> 	$(common-objpfx)cmath.
> 	($(common-objpfx)cstdlib): New target.
> 	($(common-objpfx)cmath): Likewise.

This looks good to me.

However, I'd like Florian to sign off on this solution since he's looked
at it more directly when fixing the C++ failure he saw.
  

On 30 Jun 2016 09:57, H.J. Lu wrote:
> +		| grep cstdlib: | sed -e "s/:$$//")

| sed -n "/cstdlib:/{s/:$$//;p}")
-mike