Re: [ptxdist] problem compiling gdbserver and gdb with -Wcast-align

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Wed, Sep 04, 2013 at 04:19:08PM +0200, Alexander Dahl wrote:
> at the moment we are using ptxdist 2013.07.1 with OSELAS toolchain
> 2012.12.1 for arm-v5te. We usually have set -Wcast-align in the extra
> toolchain options (TARGET_EXTRA_CFLAGS and the two for C++) to spot
> alignment problems in our code. Most software packages throw alignment
> warnings. Ignoring what this actually means, this is no problem as long
> as the package does not set -Werror. gdb sets -Werror. We tried most
> currently available versions of gdb and the build fails, e.g. like this:
> 
> /home/adahl/Work/bsp/XXX/platform-XXX/build-target/gdbserver-7.5/gdb/gdbserver/../common/agent.c:
> In function 'agent_look_up_symbols':
> /home/adahl/Work/bsp/XXX/platform-XXX/build-target/gdbserver-7.5/gdb/gdbserver/../common/agent.c:95:2:
> error: cast increases required alignment of target type
> [-Werror=cast-align]
> cc1: all warnings being treated as errors
> make[1]: *** [agent.o] Error 1
> 
> I guess one could dig into gdb sources, find and hopefully fix the
> problem, make a patch, send it to upstream and to ptxdist, wait, do all
> the usual things.
> 
> One could also drop the additional flag globally.
> 
> My question: is it possible to override the TARGET_EXTRA_CFLAGS per
> package? Maybe in rules/gdbserver.make? Or would this be a bad idea?
> 
> I'd like a quick solution where I don't have to dig into gdb source code
> and can keep the global target warnings. O:-)

An interesting problem. I think what you need is a -Wno-error=cast-align or
just -Wno-error. The problem is, that right now TARGET_EXTRA_CFLAGS are
added at the beginning of the command-line, so the -Werror from gdb will
overwrite it.
Maybe we can move the TARGET_EXTRA_CFLAGS to the end. I'm not sure if there
are any compiler flags, that must be specified at the beginning like some
of the linker flags?

Also, I think an (optional?) -Wno-error at the end would make sense.

Michael

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