Post by thread:[PIC]: A C preprocessor question

I'm wondering how / if you can do the following with symbols in the C preprocessor: I'd like to be able to write something like: #if CONFIG == c ... #elif CONFIG == d ... #endif so that I can set CONFIG to the letter c or d when invoking a compiler, e.g. picc -G -O -Zg5 -D24 -E -ASMLIST-16C77 -C -DCONFIG=c main.c I know I can do this with numbers, but is there a way I can do it with non-numeric constants? I suspect it's not possible, but thought I'd ask ... Thanks, -- ______________________________________ Andrew E. Kalman, Ph.D. spam_OUTaekTakeThisOuTpumpkininc.com -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

Of course its possible: Try this: #define c == 1 #define d == 2 #if CONFIG == c ... #elif CONFIG == d ... #endif Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) {Original Message removed}

Re: >Try this: > >#define c == 1 >#define d == 2 > >#if CONFIG == c >... >#elif CONFIG == d >... >#endif I presume you meant #define c 1 #define d 2 ... Yes, that works inside of files, but I need to define the symbol _outside_ of any file, e.g. on the compiler's command-line. I don't want to involve any other files ("include on demand") that would contain the #define directive. This is a subtle difference ... -- ______________________________________ Andrew E. Kalman, Ph.D. aekKILLspampumpkininc.com -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu

> #define c 1 > #define d 2 Yeah, that's what I meant. > > Yes, that works inside of files, but I need to define the symbol > _outside_ of any file, e.g. on the compiler's command-line. I don't > want to involve any other files ("include on demand") that would > contain the #define directive. This is a subtle difference ... inside your file: #define c 1 #define d 2 #if CONFIG == c ... #elif CONFIG == d #endif And all that has to go on the command line is: -dCONFIG=c which is, I believe, what you are looking for. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu

{Quote hidden}> > #define c 1 >> #define d 2 > >Yeah, that's what I meant. > >> >> Yes, that works inside of files, but I need to define the symbol >> _outside_ of any file, e.g. on the compiler's command-line. I don't >> want to involve any other files ("include on demand") that would >> contain the #define directive. This is a subtle difference ... > >inside your file: > >#define c 1 >#define d 2 > >#if CONFIG == c > ... >#elif CONFIG == d > >#endif > >And all that has to go on the command line is: > > -dCONFIG=c > >which is, I believe, what you are looking for. Ahhh .. so we give the char a numeric value via the #define, so that a valid comparison can be made, and we can pass any character in on the command line. Thanks, that's what I was looking for! -- ______________________________________ Andrew E. Kalman, Ph.D. aekspam_OUTpumpkininc.com -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu

> Yes, that works inside of files, but I need to define the symbol > _outside_ of any file, e.g. on the compiler's command-line. You mean rather like the -D option described below? Every c compiler I've used supports it, along with make/etc.... BillW NAME cpp - the C language preprocessor SYNOPSIS /usr/ccs/lib/cpp [ -BCHMpPRT ] [ -undef ] [ -Dname ] [ -Dname=def ] [ -Idirectory ] [ -Uname ] [ -Ydirectory ] [ input-file [ output-file ] ] : -Dname Define name as 1 (one). This is the same as if a -Dname=1 option appeared on the cpp com- mand line, or as if a #define name 1 line appeared in the source file that cpp is processing. -Dname=def Define name as if by a #define directive. This is the same as if a #define name def line appeared in the source file that cpp is processing. The -D option has lower pre- cedence than the -U option. That is, if the same name is used in both a -U option and a -D option, the name will be undefined regard- less of the order of the options. -- http://www.piclist.com hint: To leave the PICList KILLspampiclist-unsubscribe-requestKILLspammitvma.mit.edu

Re: > > Yes, that works inside of files, but I need to define the symbol >> _outside_ of any file, e.g. on the compiler's command-line. > >You mean rather like the -D option described below? Every c compiler >I've used supports it, along with make/etc.... Right - the problem I had was that I was passing -Dsymbol=c on the command line, and then doing a comparison like this: #if symbol == c which doesn't work and causes strange behavior (it seems to behave like #ifdef instead), all because c must be of integer value, which I was failing to give it. The cure, which I figured out and Bob Ammerman suggested simultaneously, is to simply give c an integer value, like: #define c 1 inside the file where the comparison is made, prior to the comparison. Regards, -- ______________________________________ Andrew E. Kalman, Ph.D. RemoveMEaekTakeThisOuTpumpkininc.com -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestspamBeGonemitvma.mit.edu