[Buildroot] [PATCH 1/2] package/Makefile.in should grab HOST_DIR headers using -isystem instead of -I.

[Khem Raj]

> On Jul 28, 2016, at 3:00 PM, Yann E. MORIN <yann.morin.1998 at free.fr> wrote:
> 
> David, All,
> 
> On 2016-07-25 15:52 -0400, David Raeman spake thusly:
>> HOST_CFLAGS includes a search path for HOST_DIR/usr/include using -I.  When
>> HOST_CFLAGS is used by a package, these flags are passed to the compiler ahead
>> of flags passed by the package's internal make system.  If a package has a
>> header file with the same name as a header file in HOST_DIR, this causes the
>> toolchain to prefer the file from the system include directory because its -I
>> appears first on the command line.  I believe conflicts should prefer the file
>> provided by the package.  This can be accomplished by using -isystem, which is
>> more appropriate then -I for system-level include paths.
> 
> This breaks building the host-python:
> 
>    Python build finished, but the necessary bits to build these modules were not found:
>    _bsddb             _curses            _curses_panel
>    _sqlite3           _ssl               _tkinter
>    bsddb185           bz2                dbm
>    dl                 gdbm               imageop
>    readline           sunaudiodev        zlib
>    To find the necessary bits, look in setup.py in detect_modules() for the module's name.
> 
> which in turn makes host-python-setuptoolss fail to build as well:
> 
>    http://autobuild.buildroot.org/?reason=host-python-setuptools-18.7.1
>    http://autobuild.buildroot.org/results/caf/cafe38622a592ac2df96306dfd9b2c9c0450e4f0/build-end.log
> 
> But the failure is really due to Python not finding the jost-zlib that
> is installed.
> 
> Could you have a look at this please?
> 
> Regards,
> Yann E. MORIN.
> 
>> Real-world example: I need libfdt present in my HOST_DIR to install a patched
>> version of QEMU.  Meanwhile, the u-boot package provides its own copy of
>> libfdt.h that is modified from upstream.  If I have libfdt installed into
>> HOST_DIR, then host-uboot-tools fails to build because it grabs the libfdt.h
>> from the HOST_DIR area instead of using the patched version from its own
>> source tree.  This patch corrects this issue.
>> 
>> This assumes the -isystem flag is supported by the host compiler.
>> 
>> Signed-off-by: David Raeman <draeman at bbn.com>
>> ---
>> package/Makefile.in | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/package/Makefile.in b/package/Makefile.in
>> index afd5d3a..b0ef706 100644
>> --- a/package/Makefile.in
>> +++ b/package/Makefile.in
>> @@ -222,7 +222,7 @@ UNZIP := $(shell which unzip || type -p unzip) -q
>> 
>> APPLY_PATCHES = support/scripts/apply-patches.sh $(if $(QUIET),-s)
>> 
>> -HOST_CPPFLAGS  = -I$(HOST_DIR)/usr/include
>> +HOST_CPPFLAGS  = -isystem $(HOST_DIR)/usr/include

This is quite intrusive change. avoid -isystems since it interferes with the
default include ordering of gcc and will cause compile failure since it wont
be able to find headers in some cases. So many packages will fail to build.
especially gcc-6.x will hit hard

>> HOST_CFLAGS   ?= -O2
>> HOST_CFLAGS   += $(HOST_CPPFLAGS)
>> HOST_CXXFLAGS += $(HOST_CFLAGS)
>> --
>> 2.7.4
>> 
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> 
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