On Thu, Mar 05, 2015 at 12:48:42PM +0100, Martin Lucina wrote:
> [adding -lm to endfile in specs]
> > > How is it needed? Why isn't pixman linking the lib in? In other words,
> > > what's the error without this patch?
> >
> > Not I check again, for some reason libm is not listed in LDLIBS. I think
> > it belongs there?
> >
> > The error is when linking QEMU, there are some undefined references
> > (IIRC sqrtf) in pixman (which is QEMU dependency).
>
> sqrtf (and indeed any of the math functions) are explicitly documented as
> "link with -lm".
>
> I ran into similar issues when linking mysqld. What I think is happening
> here is developer laziness when things "just work" on Linux (e.g. due to
> GCC substituting the calls for builtins, or the C++ toolchain always
> linking with -lm).
>
> In the case of mysqld I "fixed" the problem by doing what the Linux
> C++ toolchain does and always link with -lm. However, I'm not convinced
> that is the right thing to do for the C toolchain.
>
> Can you verify that a Linux build of qemu does not explicitly add -lm when
> linking qemu?
>
Here is the error message if I don't have -lm:
LINK i386-softmmu/qemu-system-i386
/local/scratch/Rump-kernels/rumpuser-xen/platform/xen/rump/lib/librumpnet.a(net_stub.o):
warning: multiple common of `rumpns_ifnet_list'
/local/scratch/Rump-kernels/rumpuser-xen/platform/xen/rump/lib/librumpnet_net.a(if.o):
warning: previous common is here
/local/scratch/Rump-kernels/prefix/lib/libpixman-1.a(pixman-radial-gradient.o):
In function `radial_compute_color':
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-radial-gradient.c:124:
undefined reference to `sqrt'
/local/scratch/Rump-kernels/prefix/lib/libpixman-1.a(pixman-combine32.o):
In function `blend_soft_light':
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine32.c:869:
undefined reference to `sqrt'
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine32.c:869:
undefined reference to `sqrt'
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine32.c:869:
undefined reference to `sqrt'
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine32.c:869:
undefined reference to `sqrt'
/local/scratch/Rump-kernels/prefix/lib/libpixman-1.a(pixman-combine32.o):/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine32.c:869:
more undefined references to `sqrt' follow
/local/scratch/Rump-kernels/prefix/lib/libpixman-1.a(pixman-combine-float.o):
In function `blend_soft_light':
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine-float.c:459:
undefined reference to `sqrtf'
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine-float.c:459:
undefined reference to `sqrtf'
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine-float.c:459:
undefined reference to `sqrtf'
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine-float.c:459:
undefined reference to `sqrtf'
/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine-float.c:459:
undefined reference to `sqrtf'
/local/scratch/Rump-kernels/prefix/lib/libpixman-1.a(pixman-combine-float.o):/local/scratch/Rump-kernels/rump-build-script-junk/pixman-0.32.6/pixman/pixman-combine-float.c:459:
more undefined references to `sqrtf' follow
collect2: error: ld returned 1 exit status
And an excerpt form the actual rune:
-lz -lm -pthread -L/local/scratch/Rump-kernels/prefix/lib -lgthread-2.0
-lglib-2.0 -lintl -lz -L/local/scratch/Rump-kernels/prefix/lib
-lpixman-1 -lutil
Strictly speaking, QEMU does have -lm specified. However due to the
ordering of ld rune, -lm goes before -lpixman-1, so pixman cannot find the
symbols in libm.
I think pixman should be linked against libm when building. So I now
have a patch like this:
diff --git a/platform/xen/Makefile b/platform/xen/Makefile
index e9c8f11..0b9496d 100644
--- a/platform/xen/Makefile
+++ b/platform/xen/Makefile
@@ -35,7 +35,7 @@ RUMP_LIBS_NET+= -lrumpnet_net -lrumpxen_xendev -lrumpnet
# Define some default flags for linking.
RUMP_LDLIBS = --whole-archive ${RUMP_LIBS_FS} ${RUMP_LIBS_NET}
${RUMP_LIBS_PCI} ${RUMP_LI
-RUMP_LDLIBS := ${RUMP_LDLIBS} -lpthread -lc
+RUMP_LDLIBS := ${RUMP_LDLIBS} -lpthread -lc -lm
> Martin
