emphasize that structures should be initialized to zero

doc/chapters/advanced-examples.texi

@@ -303,7 +303,9 @@ a performance model, by defining a @code{starpu_perfmodel} structure and
 providing its address in the @code{model} field of the @code{struct starpu_codelet}
 structure. The @code{symbol} and @code{type} fields of @code{starpu_perfmodel}
 are mandatory, to give a name to the model, and the type of the model, since
-there are several kinds of performance models.
+there are several kinds of performance models. For compatibility, make sure to
+initialize the whole structure to zero, either by using explicit memset, or by
+letting the compiler implicitly do it as examplified below.
 
 @itemize
 @item

doc/chapters/basic-api.texi

@@ -1259,7 +1259,9 @@ always only define the field @code{opencl_funcs}.
 
 @deftp {Data Type} {struct starpu_codelet}
 The codelet structure describes a kernel that is possibly implemented on various
-targets. For compatibility, make sure to initialize the whole structure to zero.
+targets. For compatibility, make sure to initialize the whole structure to zero,
+either by using explicit memset, or by letting the compiler implicitly do it in
+e.g. static storage case.
 
 @table @asis
 @item @code{uint32_t where} (optional)
@@ -1826,7 +1828,11 @@ The possible values are:
 @anchor{struct starpu_perfmodel}
 contains all information about a performance model. At least the
 @code{type} and @code{symbol} fields have to be filled when defining a
-performance model for a codelet. If not provided, other fields have to be zero.
+performance model for a codelet. For compatibility, make sure to initialize the
+whole structure to zero, either by using explicit memset, or by letting the
+compiler implicitly do it in e.g. static storage case.
+
+If not provided, other fields have to be zero.
 
 @table @asis
 @item @code{type}

doc/chapters/basic-examples.texi

@@ -161,7 +161,9 @@ struct starpu_codelet cl =
 
 A codelet is a structure that represents a computational kernel. Such a codelet
 may contain an implementation of the same kernel on different architectures
-(e.g. CUDA, Cell's SPU, x86, ...).
+(e.g. CUDA, Cell's SPU, x86, ...). For compatibility, make sure that the whole
+structure is initialized to zero, either by using memset, or by letting the
+compiler implicitly do it as examplified above.
 
 The @code{nbuffers} field specifies the number of data buffers that are
 manipulated by the codelet: here the codelet does not access or modify any data