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[Qemu-devel] Re: [kvm-ppc-devel] The default for char Literals differ in

From: Christian Ehrhardt
Subject: [Qemu-devel] Re: [kvm-ppc-devel] The default for char Literals differ in signedness between platforms causing us a lot of warnings
Date: Wed, 16 Jan 2008 13:29:39 +0100
User-agent: Thunderbird (X11/20071018)

the following discussion is from kvm-ppc-devel, but it is actually an qemu 
discussion so I move th topic to qemu-devel.
The original thread is cited in the mail below, in short the issue is the 

Newer gcc versions generate warnings about implicit casts between different 
signed pointers.
That hits a lot of qemu code at least what I saw it compiling for ppc or x86.
So my question is, is there already a preferred qemu approach to get rid of 
these warnings
either the -Wno-pointer-sign solution like in the kernel or something else (I 
did not find
anything like that in the latest cvs snapshot or on this list)?

--- thread from kvm-ppc-devel ---

Jimi Xenidis wrote:

On Jan 11, 2008, at 10:04 AM, Hollis Blanchard wrote:

On Fri, 2008-01-11 at 14:14 +0100, Christian Ehrhardt wrote:
maybe its an issue of my build environment only, but when I compile
kvm-userspace for our platform I see a lot of warnings like that in
the qemu code:

    warning: pointer targets in passing argument 3 of
'PPC_NVRAM_set_params' differ in signedness

The reason is that some code defines function prototypes and variables
with the type "const unsigned char*" and then assigns a literal like
"PPC" to it. But per default our platform seems to have "const signed
char*" for literals and so we get a lot of annoying warnings. E.g.
nearly every line in qemu/target-ppc/translate.c.

Should we do anything to prevent these Warnings or do you even see
those ?

That warning only appears in recent versions of gcc. In fact I believe
there are 3 different types: char *, unsigned char *, and signed char *,
and implicitly casting between them generates the warnings. :(


It's a qemu issue. If you want to fix it, you should bring it up on
qemu-devel and see what they think about it.

this is what:
# disable pointer signed / unsigned warnings in gcc 4.0
KBUILD_CFLAGS += $(call cc-option,-Wno-pointer-sign,)

In linux/Makefile is for.


GrĂ¼sse / regards, Christian Ehrhardt
IBM Linux Technology Center, Open Virtualization

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