Question: What are command tags?

[llahti]

So far i have been trying to search information what are the command tags from the documentation page http://j123b567.github.io/scpi-parser/. But i didn't find any useful information about what are those and how those should be used.

Actually reason why i am asking is that when i'm trying to compile scpilib i will get plenty of compiler warnings caused by missing command tag definition. I'm using arm-none-linux-gnueabi-g++ (ctng-1.6.1) 4.4.3 to compile this project.

Because of the missing tag definition i will get following warning

warning: missing initializer for member '_scpi_command_t::tag'

I did small search in source code and find that the command tags seems to be optional. `struct _scpi_command_t { const char * pattern; scpi_command_callback_t callback;

if USE_COMMAND_TAGS

    int32_t tag;

endif /* USE_COMMAND_TAGS */

};`

For reference I'm constructing command list by following way. const scpi_command_t scpi_commands[] = { { "*CLS", SCPI_CoreCls,}, { "*ESE", SCPI_CoreEse,},

[j123b567]

This functionality is here for sharing one callback with multiple commands. You can later detect real command in callback by its tag using SCPI_CmdTag

Example:

....
{ "CMDabcd", CMDabcd_cb, 0},
{ "CMDabcd?", CMDabcd_cb, 1},
....

scpi_result_t CMDabcd_cb(scpi_t *context) {
  if (SCPI_CmdTag(context) == 1) {
     // command is query
  } else {
     // it is standard command
  }
}

This is just a problem using c++ compiler. Using c++ compiler is not well tested so there may by lot of warnings.

You can disable this functionality by defining -DUSE_COMMAND_TAGS=0 in gcc/g++ command line for both - the library and user code. Or alternatively define -DSCPI_USER_CONFIG and use scpi_user_config.h for more configurations.

You can define your commands by

const scpi_command_t scpi_commands[] = {
 { "*CLS", SCPI_CoreCls, 0},
 { "*ESE", SCPI_CoreEse, 0},
...

to suppress this warning in g++.

[llahti]

This answers my questions very well :) Now command definitions work without warnings. Thanks.

You're right that G++ compiler produces quite a lot of warnings. I tested it with G++ 4.4.3 and 5.3.1. Regardless of warnings code is compiled successfully with G++ 5.3.1, but unfortunately our cross-compiling toolchain with G++ 4.4.3 produces errors because of isfinite(x) macro. I can provide more information about it and possible fixes tomorrow.