On 20 Mar, Joerg Schilling wrote:
>>From: [EMAIL PROTECTED]
>> ==> COMPILING "OBJ/i686-linux-cc/cdrecord.o"
>>cdrecord.c:249:1: directives may not be used inside a macro argument
>>cdrecord.c:249:1: unterminated argument list invoking macro "printf"
>>cdrecord.c: In function `main':
>>cdrecord.c:252: parse error before string constant
>>cdrecord.c:255: parse error before ')' token
>
>>This is compiled with (very) recent gcc (3.1.x). Just duplicated
>>the code such that the complete macro is contained within
>>an #if or #else part solves the problem.
>
> Unless you are on Next Step which has a buggy C-compiler that does not
> allow to have your own printf(), printf is definitely a macro!
>
> In addition, I see no reason why such an #if #else
> constructs should not be allowed in macro parameter lists but
> it seems to be a gcc limitation with parameterized macros.
> This on the other side verifies a noncompliance in GCC.
I ran into the same snag once, but not with GCC. The AIX cc has the
same problem:
% uname -a
AIX tf004i 3 4 006009434C00
% cat test.c
#define add(a, b) a + b
add( 1,
#ifdef ADD_2
2
#else
3
#endif
)
% cc -c -E test.c
#line 9 "test.c"
1 + #ifdef ADD_2 2 #else 3 #endif
I had been told that it is not guaranteed that the C preprocessor
evaluates #if #else #endif before macros. The updated edition of the
Kernigham/Ritchie C book (the one which covers ANSI C) talks about the
preprocessor in the appendix and puts token evaluation into the same
phase.
In the example above the preprocessor could have evaluated the #if
after the macro, but not with some more complex cases like
add (
#ifdef ADD_1_2
1, 2
#else
3, 4
#endif
)
which really only work when #ifdef is evaluated before the macro. Is
there really any rule in a C standard that makes the AIX and GNU C
behavior noncompliant?
Bye, Patrick Ohly
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