Strange macro, valid?

In a header I was looking at, I saw this...

Code:

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#define MMM_X(x)_Z(z)        (0x0C + (((x)-1)*3 + ((z)-1))*4)

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... is that valid? I don't recall seeing a macro like that before.

(Name changed to protect the innocent!!!)

That looks wrong to me. Where did you find it?

looks fine for me

Quote:

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Where did you find it?

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In a buildroot kernel header for a KS8695 chip.

Quote:

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Originally Posted by Mitsukai

looks fine for me

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Why does it appear fine to you :eek:
Preprocessing directive are of the form

Code:

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# define identifier replacement-list new-line

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which defines an object-like macro that causes each subsequent instance of the macro name.

or

Code:

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# define identifier lparen identifier-listopt ) replacement-list new-line

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which defines a function-like macro with parameters, similar syntactically to a function call.

the macro is FINE

the information by the OP is NOT

Code:

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#define _Z(z) (z)+
#define MMM_X(x)_Z(z)        (0x0C + (((x)-1)*3 + ((z)-1))*4)

int main()
{
  int z = 5;
  MMM_X(5);
}

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note _Z could also be a type or function!

Code:

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Your Comeau C/C++ test results are as follows:

Comeau C/C++ 4.3.9 (Mar 27 2007 17:24:47) for ONLINE_EVALUATION_BETA1
Copyright 1988-2007 Comeau Computing.  All rights reserved.
MODE:strict errors C++ noC++0x_extensions

"ComeauTest.c", line 8: warning: expression has no effect
    MMM_X(5);
    ^


In strict mode, without -tused, Compile succeeded (but remember, the Comeau online compiler does not link).
Compiled with C++0x extensions DISabled.

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Quote:

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the information by the OP is NOT

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What, pray tell, is wrong with the information in the OP? The macro appears in the header as is, (with a different name), and is the only macro in the header. All the other #defines are constant base addresses, register offsets and bit masks.

this is not a compilable example so the information by OP is not enough

Quote:

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Originally Posted by Mitsukai

the macro is FINE

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It looks wrong to me. ;)

Can you think of a sensible use which does not result in a 'redundant operation' warning ?

redundant operation?

just put int x = infront of the macro call ;)

or make _Z a function or type

Quote:

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Originally Posted by Mitsukai

redundant operation?

just put int x = infront of the macro call ;)

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Good point.
:o

Nevertheless, the macro still looks wrong to me.
:D