[systemd-devel] Build warnings for ARM due to -Wcast-align
lennart at poettering.net
Thu Feb 20 18:16:34 PST 2014
On Thu, 20.02.14 22:26, Thomas H.P. Andersen (phomes at gmail.com) wrote:
> On Thu, Feb 20, 2014 at 5:03 PM, Daniel Mack <daniel at zonque.org> wrote:
> > Hi,
> > When cross-compiling the current git HEAD for ARM using gcc 4.8.2, I see
> > ~160 warnings similar to this one:
> > src/core/unit.c: In function 'unit_get_exec_runtime':
> > src/core/unit.c:2851:17: warning: cast increases required alignment of
> > target type [-Wcast-align]
> > return *(ExecRuntime**) ((uint8_t*) u + offset);
> > ^
> > The full build log is here:
> > http://paste.fedoraproject.org/78944/92912005
> > Unaligned memory access is indeed unsupported by some older instruction
> > cores. The kernel can fix up in situations where such unaligned access
> > occurs, but that's of course expensive and slow.
> > However, systemd does not actually do unaligned memory access at runtime
> > (at least I haven't seen any when booting up PXA3xx hardware). The
> > warning is simply about the type of pointer arithmetic that casts to and
> > from uint8_t*.
> > And because it's practically impossible to fix the things the compiler
> > complains about here anyway, I propose removing -Wcast-align from the
> > CFLAGS in configure.ac.
> > Any opinions?
> Clang also caught those. I had to add -Wno-cast-align in the
> autogen-shortcut to keep the noise down. It would be nice not to have
> to do that of course.
I have removed the switch now.
Lennart Poettering, Red Hat
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