This is the error I get when compiling with Sun Studio 11:

source='exo-tree-view.c' object='libexo_0_3_la-exo-tree-view.lo' libtool=yes \
DEPDIR=.deps depmode=none /bin/bash ../depcomp \
/bin/bash ../libtool --tag=CC --mode=compile /opt/SUNWspro/bin/cc -DHAVE_CONFIG_H -I. -I. -I.. -I..                                                      -DDATADIR=\"/opt/Xfce-beta/share\"                                      -DEXO_API_SUBJECT_TO_CHANGE                                     -DEXO_COMPILATION              -DG_LOG_DOMAIN=\"exo\"                                           -DLIBEXECDIR=\"/opt/Xfce-beta/libexec\"                                         -DLIBEXO_VERSION_API=\"0.3\"                    -DPACKAGE_LOCALE_DIR=\"/opt/Xfce-beta/share/locale\"   -I/opt/Xfce-beta/include/gtk-2.0 -I/opt/Xfce-beta/lib/gtk-2.0/include -I/opt/Xfce-beta/include/atk-1.0 -I/opt/Xfce-beta/include/cairo -I/opt/Xfce-beta/include/pango-1.0 -I/opt/Xfce-beta/include/glib-2.0 -I/opt/Xfce-beta/lib/glib-2.0/include -I/opt/Xfce-beta/include/freetype2 -I/opt/Xfce-beta/include -I/opt/Xfce-beta/include/libpng12                                                   -I/opt/Xfce-beta/include/xfce4 -I/opt/Xfce-beta/include/glib-2.0 -I/opt/Xfce-beta/lib/glib-2.0/include -g -DNDEBUG -DG_DISABLE_CAST_CHECKS -DG_DISABLE_ASSERT -DG_DISABLE_CHECKS -c -o libexo_0_3_la-exo-tree-view.lo `test -f 'exo-tree-view.c' || echo './'`exo-tree-view.c
 /opt/SUNWspro/bin/cc -DHAVE_CONFIG_H -I. -I. -I.. -I.. -DDATADIR=\"/opt/Xfce-beta/share\" -DEXO_API_SUBJECT_TO_CHANGE -DEXO_COMPILATION -DG_LOG_DOMAIN=\"exo\" -DLIBEXECDIR=\"/opt/Xfce-beta/libexec\" -DLIBEXO_VERSION_API=\"0.3\" -DPACKAGE_LOCALE_DIR=\"/opt/Xfce-beta/share/locale\" -I/opt/Xfce-beta/include/gtk-2.0 -I/opt/Xfce-beta/lib/gtk-2.0/include -I/opt/Xfce-beta/include/atk-1.0 -I/opt/Xfce-beta/include/cairo -I/opt/Xfce-beta/include/pango-1.0 -I/opt/Xfce-beta/include/glib-2.0 -I/opt/Xfce-beta/lib/glib-2.0/include -I/opt/Xfce-beta/include/freetype2 -I/opt/Xfce-beta/include -I/opt/Xfce-beta/include/libpng12 -I/opt/Xfce-beta/include/xfce4 -I/opt/Xfce-beta/include/glib-2.0 -I/opt/Xfce-beta/lib/glib-2.0/include -g -DNDEBUG -DG_DISABLE_CAST_CHECKS -DG_DISABLE_ASSERT -DG_DISABLE_CHECKS -c exo-tree-view.c  -KPIC -DPIC -o .libs/libexo_0_3_la-exo-tree-view.o
"../exo/exo-config.h", line 32: warning: syntax error:  empty declaration
"../exo/exo-config.h", line 94: warning: syntax error:  empty declaration
"/opt/Xfce-beta/include/gtk-2.0/gtk/gtktextbuffer.h", line 52: warning: enumerator value overflows INT_MAX (2147483647)
"/opt/Xfce-beta/include/gtk-2.0/gtk/gtktextbuffer.h", line 53: warning: enumerator value overflows INT_MAX (2147483647)
"/opt/Xfce-beta/include/gtk-2.0/gtk/gtktextbuffer.h", line 55: warning: enumerator value overflows INT_MAX (2147483647)
"../exo/exo-private.h", line 34: warning: syntax error:  empty declaration
"../exo/exo-private.h", line 104: warning: syntax error:  empty declaration
"../exo/exo-string.h", line 32: warning: syntax error:  empty declaration
"../exo/exo-string.h", line 55: warning: syntax error:  empty declaration
"../exo/exo-tree-view.h", line 30: warning: syntax error:  empty declaration
"../exo/exo-tree-view.h", line 80: warning: syntax error:  empty declaration
"../exo/exo-utils.h", line 30: warning: syntax error:  empty declaration
"../exo/exo-utils.h", line 84: warning: syntax error:  empty declaration
"exo-tree-view.c", line 116: warning: argument #4 is incompatible with prototype:
        prototype: pointer to void : "../exo/exo-private.h", line 93
        argument : pointer to function(pointer to struct _ExoTreeViewClass {struct _GtkTreeViewClass {..} __parent__, pointer to function(..) returning void reserved1, pointer to function(..) returning void reserved2, pointer to function(..) returning void reserved3, pointer to function(..) returning void reserved4, pointer to function(..) returning void reserved5, pointer to function(..) returning void reserved6, pointer to function(..) returning void reserved7, pointer to function(..) returning void reserved8}) returning void
"exo-tree-view.c", line 116: warning: argument #6 is incompatible with prototype:
        prototype: pointer to void : "../exo/exo-private.h", line 93
        argument : pointer to function(pointer to struct _ExoTreeView {struct _GtkTreeView {..} __parent__, pointer to struct _ExoTreeViewPrivate {..} priv}) returning void
"exo-tree-view.c", line 614: void function cannot return value
cc: acomp failed for exo-tree-view.c
*** Error code 1
dmake: Fatal error: Command failed for target `libexo_0_3_la-exo-tree-view.lo'
Current working directory /data/Xfce-beta-src/xfce/exo-0.3.1.9svn-r22981/exo
*** Error code 1
dmake: Fatal error: Command failed for target `all'