Hi,
Compilation of the below code fails
cat test.c
#define a this1, /* Comma is intentional line 1*/
#define fun( x, y, z) y*x*z/*line 2*/
char this1,b,c;/*line 3*/
int main()/*line 4*/
{
fun(b, a c); /*Comma is leftout intetionaly line 5*/
}/*line 6*/
with errors as below
gcc test.c
test.c:8:15: macro "fun" requires 3 arguments, but only 2 given
test.c: In function `main':
test.c:8: error: `fun' undeclared (first use in this function)
test.c:8: error: (Each undeclared identifier is reported only once
test.c:8: error: for each function it appears in.)
If I just change line 1 and line 5 as below it works obviously.
I want to compile the original above code as it is just a snippet of
my project ! Please help.
"#define a this1," to "#define a this1"
"fun(b, a c);" to "fun(b, a, c);" (as below)then it works fine.
cat test.c
#define a this1, /*line 1*/
#define fun( x, y, z) y*x*z/*line 2*/
char this1,b,c;/*line 3*/
int main()/*line 4*/
{
fun(b, a c);/*line 5*/
}/*line 6*/ 6 1991
On Jul 3, 11:18 am, Subra <mailursu...@gmail.comwrote:
Hi,
Compilation of the below code fails
cat test.c
#define a this1, /* Comma is intentional line 1*/
#define fun( x, y, z) y*x*z/*line 2*/
char this1,b,c;/*line 3*/
int main()/*line 4*/
{
fun(b, a c); /*Comma is leftout intetionaly line 5*/
}/*line 6*/
with errors as belowgcc test.c
test.c:8:15: macro "fun" requires 3 arguments, but only 2 given
test.c: In function `main':
Macro arguments are not expanded until after the macro itself is
expanded. When the "fun" macro is expanded only 2 arguments are
provided instead of the required 3 which is a constraint violation.
Robert Gamble
Macro arguments are not expanded until after the macro itself is
expanded. When the "fun" macro is expanded only 2 arguments are
provided instead of the required 3 which is a constraint violation.
Any preprocessor option to avoid this ???
Subra <ma*********@gmail.comwrites:
>Macro arguments are not expanded until after the macro itself is expanded. When the "fun" macro is expanded only 2 arguments are provided instead of the required 3 which is a constraint violation.
The above was written by Robert Gamble. Please don't delete
attribution lines.
Any preprocessor option to avoid this ???
I doubt it.
The C standard doesn't specify "options" to the preprocessor or to the
compiler; it merely specifies how the compiler is required to behave.
You wrote a macro that requires 3 arguments, and you passed it only 2
arguments. That's a constraint violation, and a diagnostic is
required; in most implementations, the compilation will be rejected.
The solution is to change the macro so it requires 2 arguments, or to
change the invocation so it passes 3 arguments.
C99 introduces variadic macros; your compiler may or may not support
them. But I don't know if that's really what you're looking for.
What are you really trying to do?
--
Keith Thompson (The_Other_Keith) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
On Jul 4, 7:05 am, Keith Thompson <k...@mib.orgwrote:
Subra <mailursu...@gmail.comwrites:
Macro arguments are not expanded until after the macro itself is
expanded. When the "fun" macro is expanded only 2 arguments are
provided instead of the required 3 which is a constraint violation.
Any preprocessor option to avoid this ???
I doubt it.
The C standard doesn't specify "options" to the preprocessor or to the
compiler; it merely specifies how the compiler is required to behave.
You wrote a macro that requires 3 arguments, and you passed it only 2
arguments. That's a constraint violation, and a diagnostic is
required; in most implementations, the compilation will be rejected.
The solution is to change the macro so it requires 2 arguments, or to
change the invocation so it passes 3 arguments.
C99 introduces variadic macros; your compiler may or may not support
them. But I don't know if that's really what you're looking for.
What are you really trying to do?
I have third party library which was taking 2 args for a macro as
below.
_RW_VAL_ALLOC(a,b) a*b // It is used by platforms HPUX, Solaris
Now the new version of library takes 3 args
_RW_VAL_ALLOC(a,c,b) c*a*b // It is used by LINUX
My code which makes the call to _RW_VAL_ALLOC have to select different
versions
of the macro depending on the platfrom
So my code is like below
#if defined(NEW_VERSION_RW)
#define PIN_ALLOC_VAL argPresnt,
#else
#define PIN_ALLOC_VAL
#endif
int main()
{
int a, b, argPresent;
_RW_VAL_ALLOC(a,
PIN_ALLOC_VAL // Only when we use the new version of
lib, it should get
// replaced by a arg.
b);
}
This solution is not working.
On Jul 4, 12:21 am, Subra <mailursu...@gmail.comwrote:
On Jul 4, 7:05 am, Keith Thompson <k...@mib.orgwrote:
Subra <mailursu...@gmail.comwrites:
>Macro arguments are not expanded until after the macro itself is
>expanded. When the "fun" macro is expanded only 2 arguments are
>provided instead of the required 3 which is a constraint violation.
Any preprocessor option to avoid this ???
I doubt it.
The C standard doesn't specify "options" to the preprocessor or to the
compiler; it merely specifies how the compiler is required to behave.
You wrote a macro that requires 3 arguments, and you passed it only 2
arguments. That's a constraint violation, and a diagnostic is
required; in most implementations, the compilation will be rejected.
The solution is to change the macro so it requires 2 arguments, or to
change the invocation so it passes 3 arguments.
C99 introduces variadic macros; your compiler may or may not support
them. But I don't know if that's really what you're looking for.
What are you really trying to do?
I have third party library which was taking 2 args for a macro as
below.
_RW_VAL_ALLOC(a,b) a*b // It is used by platforms HPUX, Solaris
Now the new version of library takes 3 args
_RW_VAL_ALLOC(a,c,b) c*a*b // It is used by LINUX
My code which makes the call to _RW_VAL_ALLOC have to select different
versions
of the macro depending on the platfrom
So my code is like below
#if defined(NEW_VERSION_RW)
#define PIN_ALLOC_VAL argPresnt,
#else
#define PIN_ALLOC_VAL
#endif
int main()
{
int a, b, argPresent;
_RW_VAL_ALLOC(a,
PIN_ALLOC_VAL // Only when we use the new version of
lib, it should get
// replaced by a arg.
b);
}
This solution is not working.
How about this:
<==CUT==>
#if defined(NEW_VERSION_RW)
#define MY_RW_VAL_ALLOC(a, c, b) _RW_VAL_ALLOC(a, c, b)
#else
#define MY_RW_VAL_ALLOC(a, c, b) _RW_VAL_ALLOC(a, b)
#endif
MY_RW_VAL_ALLOC(a, c, b)
<==CUT==>
$ gcc -E test.c
_RW_VAL_ALLOC(a, b)
$ gcc -E -DNEW_VERSION_RW test.c
_RW_VAL_ALLOC(a, c, b)
Robert Gamble
On Jul 4, 9:32 am, Robert Gamble <rgambl...@gmail.comwrote:
On Jul 4, 12:21 am, Subra <mailursu...@gmail.comwrote:
On Jul 4, 7:05 am, Keith Thompson <k...@mib.orgwrote:
Subra <mailursu...@gmail.comwrites:
Macro arguments are not expanded until after the macro itself is
expanded. When the "fun" macro is expanded only 2 arguments are
provided instead of the required 3 which is a constraint violation.
Any preprocessor option to avoid this ???
I doubt it.
The C standard doesn't specify "options" to the preprocessor or to the
compiler; it merely specifies how the compiler is required to behave.
You wrote a macro that requires 3 arguments, and you passed it only 2
arguments. That's a constraint violation, and a diagnostic is
required; in most implementations, the compilation will be rejected.
The solution is to change the macro so it requires 2 arguments, or to
change the invocation so it passes 3 arguments.
C99 introduces variadic macros; your compiler may or may not support
them. But I don't know if that's really what you're looking for.
What are you really trying to do?
I have third party library which was taking 2 args for a macro as
below.
_RW_VAL_ALLOC(a,b) a*b // It is used by platforms HPUX, Solaris
Now the new version of library takes 3 args
_RW_VAL_ALLOC(a,c,b) c*a*b // It is used by LINUX
My code which makes the call to _RW_VAL_ALLOC have to select different
versions
of the macro depending on the platfrom
So my code is like below
#if defined(NEW_VERSION_RW)
#define PIN_ALLOC_VAL argPresnt,
#else
#define PIN_ALLOC_VAL
#endif
int main()
{
int a, b, argPresent;
_RW_VAL_ALLOC(a,
PIN_ALLOC_VAL // Only when we use the new version of
lib, it should get
// replaced by a arg.
b);
}
This solution is not working.
How about this:
<==CUT==>
#if defined(NEW_VERSION_RW)
#define MY_RW_VAL_ALLOC(a, c, b) _RW_VAL_ALLOC(a, c, b)
#else
#define MY_RW_VAL_ALLOC(a, c, b) _RW_VAL_ALLOC(a, b)
#endif
MY_RW_VAL_ALLOC(a, c, b)
<==CUT==>
$ gcc -E test.c
_RW_VAL_ALLOC(a, b)
$ gcc -E -DNEW_VERSION_RW test.c
_RW_VAL_ALLOC(a, c, b)
Robert Gamble
I will be using the above fix ! Thank you Robert. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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