All Questions
Tagged with variadic-macros c99
16 questions
0
votes
1
answer
58
views
Macro with number of arguments AND default parameter
I'm familiar with the following way of creating a macro with variable number of arguments. However, consider:
#define MY_MACRO_N(value, format, ...) my_func(value, format, ##__VA_ARGS__)
#define ...
- 3,933
3
votes
2
answers
125
views
Variadic macro expansion's going wrong
Consider the following code
#define COMB(F, ...) F(__VA_ARGS__)
#define ADD(X, Y) (X + Y)
int foo() {
return COMB(ADD, 1, 2);
}
I have done some experiments on Godbolt. Microsoft VS v19.22 (...
- 1,271
2
votes
1
answer
2k
views
C preprocessor macro doesn't parse comma separated tokens?
I want to choose one of two functions depending on the number of arguments:
nargs = 0 ----> f1
nargs > 0 ----> f2.
Macros do the following: get the first argument, then if no argument supplied ,...
- 541
0
votes
0
answers
39
views
Apply a macro to a variable argument list [duplicate]
I have a variadic macro and a regular macro. I use them like this:
LIST(
ELEM(a),
ELEM(b)
// usually about 4-8 elements
)
I would like LIST to automatically invoke ELEM on each argument so ...
- 5,311
4
votes
3
answers
1k
views
C99 compatible nested calls within variadic macros
Need a way to support nested calls in variadic macros with optional argument. same as this but C99 compatible
GNU gcc extension for ## operator prevents nested calls from being expanded, see code ...
- 191
0
votes
2
answers
550
views
C99 Macro Expansion for Struct Member Access
Is it possible to do a nullity check and an access in a macro?
Eg:
#define LOG(mystruct, severity, format, ...) ({ \
severity_t current = ERROR; \
if (mystruct) { \
current = mystruct->...
- 921
0
votes
2
answers
142
views
Variadic function in C99 to deallocate several arrays?
Currently, I have a very simple function to deallocate array of doubles in my program:
void deallocate(double** array)
{
free(*array);
}
I would like this function to be variadic in order to ...
- 60.2k
1
vote
1
answer
3k
views
Checking if an argument is passed in variadic macros in C
For cleaner error handling I use a macro (it uses C99 and GCC extensions); the behavior is like standard assert:
#define A(cond, msg, ...) ({ \
if (!(cond)) { \
if (msg) \
...
user1150105
2
votes
2
answers
2k
views
reverse the arguments to a variadic macro
How do I reverse the arguments to a variadic macro? For example, I'd like
#define REVERSE(...) ???
REVERSE(A,B,C) // expands to C,B,A
My goal is to separate the front and back arguments:
#define ...
- 2,509
0
votes
2
answers
668
views
How to expand variadic arguments in a macro?
I want to essentially have a macro shortener.
The macro, FOO(A,B,C) should expand to
defined(_FOO_A) || defined(_FOO_B) || defined(_FOO_C).
Is that possible in GCC using variadic macro arguments and ...
- 342
5
votes
1
answer
5k
views
Avoiding "ISO C99 requires rest arguments to be used"
With gcc 4.6.3 (with -ansi -pedantic), I've got the following code:
// Argument counting macro
#define NARGS(...) NARGS_(__VA_ARGS__, 5, 4, 3, 2, 1)
#define NARGS_(_1, _2, _3, _4, _5, _, ...) _
...
- 14.5k
13
votes
1
answer
11k
views
Cleaning up C/C++ code reveals problems with variadic macros
We're doing some code cleanup, fixing signed/unsigned comparisons, running static analysis, etc, on the code base of C, C++, and Java.
One of the warnings we're getting is
warning: ISO C does not ...
- 2,960
171
votes
12
answers
109k
views
Standard alternative to GCC's ##__VA_ARGS__ trick?
There is a well-known problem with empty args for variadic macros in C99.
example:
#define FOO(...) printf(__VA_ARGS__)
#define BAR(fmt, ...) printf(fmt, __VA_ARGS__)
FOO("this works fine");
...
- 11.1k
4
votes
2
answers
7k
views
Generating function declaration using a macro iteration
I'm trying to generate a function declaration using a macro
/* goal: generate int f(int a, float b) */
template<typename P>
struct ptype;
template<typename P>
struct ptype<void(P)>...
7
votes
2
answers
16k
views
Can I define variadic C preprocessor macros with __VA_ARGS in the middle instead of the end?
GCC complains if I do this:
#define M(obj,met, ..., contents) obj##_##met(const void * self, __VA_ARGS__) { \
contents \
}
Giving me these 2 reasons:
error: missing ')' in macro parameter ...
- 2,995
6
votes
3
answers
2k
views
Token pasting in C
After reading about VA_NARG
I tried to implement function overloading depending on number of arguments in C using macros.
Now the problem is:
void hello1(char *s) { ... }
void hello2(char *s, char *...
- 2,451