string constant in macro

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Read-Only Author Anh Phan Posted 3-Jul-2004 00:57 GMT Toolset C51	string constant in macro Anh Phan Hello, In my C code, I have: #define message message("Start\n"); When I look at the SRC file, I see: RSEG ?CO?MAIN ?SC_0: DB 'S' ,'t' ,'a' ,'r' ,'t' ,00AH,000H ; message("Start\n"); Why does the C51 version 1.32 keep "Start\n" in the output? Does this also happen to newer version? Thanks, Anh

Read-Only Author Andy Neil Posted 3-Jul-2004 01:11 GMT Toolset C51	RE: string constant in macro Andy Neil "Why does the C51 version 1.32 keep "Start\n" in the output?" If you don't want it, why did you put it there?!

Read-Only Author Anh Phan Posted 3-Jul-2004 02:04 GMT Toolset C51	RE: string constant in macro Anh Phan What I mean is that I have the code: #define message . . . message("Start\n"); message("Start\n") should expands to nothing so "Start\n" should not be in the output Anh

Read-Only Author Drew Davis Posted 3-Jul-2004 03:18 GMT Toolset C51	RE: string constant in macro Drew Davis The macro expands to nothing, but the literal string constant still exists. How about another #define to make the constant vanish: //#define MessageString "Start\n" #define MessageString #define message(a) ... message(MessageString)

Read-Only Author Jon Ward Posted 3-Jul-2004 05:19 GMT Toolset C51	RE: string constant in macro Jon Ward Why does the C51 version 1.32 keep "Start\n" in the output? Does this also happen to newer version? It does it because that is what you told the compiler to do. The line #define message defines a null macro for message. The line message("Start\n"); expands as ("Start\n"); I can only assume that what you want is: #define message(x) message("Start\n") Jon

Read-Only Author Andy Neil Posted 3-Jul-2004 06:50 GMT Toolset C51	RE: string constant in macro Andy Neil I don't know if this thread might help you: http://www.keil.com/forum/docs/thread3796.asp It shows (among other things) how to define a debug TRACE macro that can dissappear completely when the code is built in non-debug mode. The secret is in the use of an extra set of parenteses.

Read-Only Author Anh Phan Posted 4-Jul-2004 01:29 GMT Toolset C51	RE: string constant in macro Anh Phan Thanks guys, Your responses really help me a lot. Looks like the TRACE macro is what I need to remove unnessary code. Is there a way to expand a macro into // to comment out the code? Ex: #define message // so that message("Start\n"); would expand to: //("Start\n"); Anh

Read-Only Author Drew Davis Posted 4-Jul-2004 02:53 GMT Toolset C51	RE: string constant in macro Drew Davis How about: #define comment /##/ '##' is the "token pasting' operator that lets you glue bits together into a single token for the compiler.

Read-Only Author Andrew Neil Posted 5-Jul-2004 13:28 GMT Toolset C51	RE: string constant in macro Andrew Neil Sounds like a very bad idea to me. remember, it's the preprocessor that does macro expansion, and it's also the prepropcessor that strips comments... Far better to make your macro expansion explicitly & directly conditional (as described in the TRACE example), than rely on the order of macro "side-effects"...

Read-Only Author Drew Davis Posted 5-Jul-2004 18:46 GMT Toolset C51	RE: string constant in macro Drew Davis I'd agree. (My previous post was answering the question asked, rather than recommending a strategy. See the linked thread in which I make other comments.)

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