Echelon FTXL - Manual (Page 55)

FTXL User’s Guide 43
Writing Acceptable Neuron C Code
When processing the model file, the LonTalk Interface Developer utility
distinguishes between three categories of Neuron C statements:
• Acceptable
• Ignored – ignored statements produce a warning
• Unacceptable – unacceptable statements produce an error
Appendix B, Model File Compiler Directives , on page 119, lists the acceptable
and ignored compiler directives for model files. All other compiler directives are
not accepted by the LonTalk Interface Developer utility and cause an error if
included in a model file. A statement can be unacceptable because it controls
features that are meaningless in an FTXL device, or because it refers to
attributes that are determined by the FTXL protocol stack or by other means.
The LonTalk Interface Developer utility ignores all executable code and I/O
object declarations. These constructs cause the LonTalk Interface Developer
utility to issue a warning message. The LonTalk Interface Developer utility
predefines the _FTXL and _MODEL_FILE macros, so that you can use #ifdef or
#ifndef compiler directives to control conditional compilation of source code that
is used for standard Neuron C compilation and as an FTXL model file.
All constructs not specifically mentioned as unacceptable or ignored are
acceptable.
Anonymous Top-Level Types
Anonymous top-level types are not acceptable. The following Neuron C construct
is not acceptable:
network output struct {int a; int b;} nvoZorro;
This statement is not acceptable because the type of the nvoZorro network
variable does not have a name. The LonTalk Interface Developer utility issues
an error when it detects such a construct.
Using a named type solves the problem, for example:
typedef struct {
int a;
int b;
} Zorro;
network output Zorro nvoZorro;
The use of anonymous sub-types is permitted. For example, the LonTalk
Interface Developer utility allows the following type definition:
typedef struct {
int a;
int b;
struct {
long x;
long y;
long z;
} c;
} Zorro;
network output Zorro nvoZorro;