[OE-core] [PATCH] cmake: add CMAKE_SYSROOT to generated toolchain file

[Mikko.Rapeli at bmw.de]

On Fri, Aug 24, 2018 at 09:23:45AM -0700, Khem Raj wrote:
> On Fri, Aug 24, 2018 at 9:17 AM <Mikko.Rapeli at bmw.de> wrote:
> >
> > On Fri, Aug 24, 2018 at 08:51:42AM -0700, Khem Raj wrote:
> > > On Fri, Aug 24, 2018 at 8:48 AM <Mikko.Rapeli at bmw.de> wrote:
> > > > So to me it looks like using SYSTEM with target_include_directories()
> > > > is no longer possible with CMake and gcc > 6:
> > > >
> > > >
> > > > https://cmake.org/cmake/help/v3.10/command/target_include_directories.html?highlight=target_include_directories
> > > >
> > >
> > > That’s right there is a patch I did  in WebKitgtk recipe in Oe Core you
> > > might want to include similar fixes for this package the patch actually it
> > > a workaround but then I also think using isystem in apps is a bad idea
> >
> > Yes, I tend to agree, but developers have used this to silence compiler
> > warnings from system header files.
> >
> > In a few cases I saw that there were no longer any warnings coming from the
> > headers but in some others there were.
> >
> 
> Unlike olden days, cross gcc compiler now a days knows about its
> system headers and adds them implicitly with right options
> so doing this include dance manually is not useful. Let compiler
> decide to do the needed
> for system headers, one must just specify --sysroot and let it handle
> everything from sysroot.
> 
> > Any other ideas how to suppress compiler wanings from system headers?
> >
> 
> what kind of warnings do you see ?

After a ton of components have exported their headers to system paths,
I see all kinds of crap. Some developers have cleaned up their own tree
and added strict compiler flags, which I now have to relax since
header file warning suppressions don't work, and new compiler produces
new bunch of warnings. Here are few sample warnings from an ongoing build
with counts redacted:

$ egrep -ho "warning: .*" tmp-glibc/work/*/*/*/temp/log.do_compile| sort | uniq -c|sort -rn | head -8

warning: dynamic exception specifications are deprecated in C++11 [-Wdeprecated]
warning: 'template<class> class std::auto_ptr' is deprecated [-Wdeprecated-declarations]
warning: conversion to 'int' from 'long unsigned int' may alter its value [-Wconversion]
warning: missed loop optimization, the loop counter may overflow [-Wunsafe-loop-optimizations]
warning: command line option '-std=c++11' is valid for C++/ObjC++ but not for C
warning: this statement may fall through [-Wimplicit-fallthrough=]
warning: ISO C++ forbids zero-size array 'f_handle' [-Wpedantic]

-Mikko