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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH] CPPFLAGS+= in Makefile.target
Date: Fri, 25 Jan 2008 15:53:36 +0000
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To: qemu-devel@nongnu.org
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>

On Friday 25 January 2008, Ian Jackson wrote:
> Paul Brook writes ("Re: [Qemu-devel] [PATCH] CPPFLAGS+= in 
Makefile.target"):
> > In that case you should always provide a definition in config-host.mak.
> > Under some circumstances make may inherit initial values from elsewhere.
>
> What circumstances ?  CPPFLAGS+= overrides (discards) values in the
> environment as well as ones from the command line.

$ cat Makefile
FOO += World
all:
        @echo "$(FOO)"
$ FOO=Hello make
Hello World