1

I've went through a number of similar questions and almost got it to work, but not quite.

What I have is the standard Macro-Expansion-Stringification-method.

#define QUOTEME(M)          #M
#define DOQUOTE(M)          QUOTEME(M)
#define XCONCAT(X, Y)       X##Y
#define CONCAT(X, Y)        XCONCAT(X, Y)

Then I have a macro PREFIX like this:

#define SW_PREFIX    XY2Ar-

What I was trying to do was:

#define SW_FILE DOQUOTE(CONCAT(SW_PREFIX, update))

What this is supposed to output is: "XY2Ar-update" What it outputs on my GCC-type compiler is:

error: pasting "-" and "update" does not give a valid preprocessing token

Now, I assume that he's replacing the macro correctly, but apparently doesn't want to append update to XY2Ar- because of the -.

I also tried:

#define SW_FILE     DOQUOTE(SW_PREFIX.update)

which, once again, almost does what I want, however it outputs XY2Ar-.update, which is not what I want either.

I'm out of ideas.

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3 Answers 3

Reset to default
3

Here is an alternative:

#define QUOTEME(M)    #M
#define COMPOSE(A, B) QUOTEME(A) #B

#define SW_PREFIX     XY2Ar-
#define SW_FILE       COMPOSE(SW_PREFIX, update)
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5 Comments

I did think that I tried something like that before. Error message: error: pasting ""XY2Ar-"" and ""update"" does not give a valid preprocessing token. Thanks for the input though.
@RefugnicEternium: You're right, sorry. That was messed up. Check now, I think this works. I think it has to be asymmetric in the two arguments, because one is a bareword and the other needs replacement. Demo.
This seems to work, though I think, quite personally, that my solution is a little less...shall we say 'verbose', wouldn't you agree? ;) I discovered it shortly after I left the comment on your previous solution.
@RefugnicEternium: Yes, absolutely. Feel free to make yours the accepted answer. (That said, your answer also changed the question by allowing SW_PREFIX to be a string rather than a bareword, so it's somewhat different situation.)
Yes, I understand that the situation is a different one, which is why yours remains the accepted one. Otherwise, Jens' answer has a very similar effect to that end.
3

Your thinking seems too complicated :-) Do not create a single token to stringify. Simply use string concatenation for separate parts.

$ cat x.c
#define QUOTEME(M) #M
#define DOQUOTE(M) QUOTEME(M)

#define SW_PREFIX    XY2Ar-
#define SW_FILE  DOQUOTE(SW_PREFIX) QUOTEME(.update)

char *x = SW_FILE;
$ gcc -E x.c
# 1 "x.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "x.c"
char *x = "XY2Ar-" ".update";
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1 Comment

Yeah, I get that a lot. I also came to the same conclusion a little while ago. Thanks for pointing it out again though. :)
1

Sometimes I keep finding myself forgetting the KISS-principle...and it's times like these where it shows.

#define SW_PREFIX   "XY2Ar-"
#define SW_FILE     SW_PREFIX"update"

These simple lines, no further expansion or anything return the desired output. As for the reason why it does that:

Since there aren't any # in there, it expands SW_PREFIX to "XY2Ar-" and appends "update" to it, which results in "XY2Ar-""update", which, for the compiler, is the same as XY2Ar-update.

Thanks to the guy who erased his answers for reminding me.

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