Re: global pgm variable and file field with same name and attributes

On 2011/1/25 10:30 AM, David FOXWELL wrote:

In the code, a file containing field GPGMID is read into display file
field EPGMID. Then the global variable gPgmId is populated with
EPGMID, read from a subfile.

In the compiler listing, GPGMID appears once in the list of global
variables. The source numbers next to it show that it does not seem
to differentiate between the global variable declared by the
programmer and the global field from the file.

So can anyone tell me what is actually happening in the program ? I
think there is a danger that by coding gPgmId = EPGMID; It is really
initialising the file field GPGMID.

David, there isn't a separate file field within the RPG program.

When you code an externally-described file in an RPG program, the compiler generates I and O specs* for the file. Those I and O specs are not really definitions, they are just descriptions of the fields in the Input and Output buffers for the file.

If the compiler doesn't find an explicit global definition for a field that appears on an I or O spec, the compiler will implicitly define a field in the program.

* In V6R1, if you define the file in a subprocedure or with the QUALIFIED keyword, the compiler doesn't generate any I and O specs, so it doesn't create any implicit definitions for the external fields.