We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.
I'm trying to use the ax51 standard macro assembler to find a way to determine if a symbol or label is already defined. Something like the following pseudo code:
if label "table_abc" is defined, do nothing, else do the following: table_abc: DB 1 DB 2 DB 3 endif
I somehow thought the following could work but alas it does not: IF NOT :DEF:table_abc table_abc: DB 1 DB 2 DB 3 ENDIF
-> LABEL NOT PERMITTED, SYNTAX ERROR
My code is 100 percent assembler code so I try to not use the C preprocessor. But if there is no other way, a C preprocessor code example would help as well.
EFM8BB31, Silicon Labs Simplicity Studio v3, Keil 8051 v9.53 debug
It still works with the C precompiler in this way:
#ifndef DEF_table_abc #define DEF_table_abc table_abc: DB 1 DB 2 DB 3 #endif
It would have been nicer with a macro assembler solution but I guess I can get used to some C preprocessor lines. Thanks for the comments.
No, that construct doesn't "work", because it does not do what you originally said you wanted to do. It does not detect whether a label is defined ... it checks whether a macro is defined. That's really quite a different thing.
Nor does it fulfill the underlying secret goal you revealed later, about taking care of things the user might have forgotten to do. This construct will still fail just as badly as an unprotected label definition, because a user who didn't know they were supposed to define that label will be equally uninformed about the need to define some macro, on top of that.
You are right, this solution won't help for an uninformed user. Thanks.