Hi folks,
My Solaris/SPARC compiles (with gcc-3.4.6) die with an alignment warning
in packet-diameter.c:
packet-diameter.c: In function `dissect_diameter_avp':
packet-diameter.c:340: warning: cast increases required alignment of target type
(followed by several more such warnings)
The relevant code for the first warning is:
109 typedef struct _diam_vnd_t {
110 guint32 code;
111 GArray* vs_avps;
112 GArray* vs_cmds;
113 } diam_vnd_t;
[...]
126 #define VND_AVP_VS(v) ((value_string*)((v)->vs_avps->data))
[...]
319 const diam_vnd_t* vendor;
[...]
340 vendor_avp_vs = VND_AVP_VS(vendor);
GArray comes from GLIB's garray.h:
34 typedef struct _GArray GArray;
[...]
38 struct _GArray
39 {
40 gchar *data;
41 guint len;
42 };
The Solaris buildbot is not getting this warning but I think the warning
is valid: an array of chars may not be aligned correctly to be accessed
as a 'value_string' (a guint32 followed by a pointer). And it may cause
bus errors because GArrays make copies of the data passed in--so we have
no guarantee how it will be aligned.
Unfortunately GArrays come in only 3 flavors: with pointers to chars,
pointers to guint8s, and pointers to pointers.
Is there an easy way to solve this?
Adding an intermediate cast to void*:
#define VND_AVP_VS(v) ((value_string*)(void*)((v)->vs_avps->data))
solves the warning and it appears this is the approach used by the glib
team:
http://svn.gnome.org/viewvc/glib?view=revision&revision=6092
but I don't think it's correct. But at the moment I also think the
example (storing gint values) used in the GArrays documentation:
http://library.gnome.org/devel/glib/unstable/glib-Arrays.html
is also not correct/safe on SPARCs. Can someone please tell me I'm wrong?
