C / C++: Difference between revisions
Jump to navigation
Jump to search
No edit summary |
(→C) Tag: Replaced |
||
| Line 2: | Line 2: | ||
== C == |
== C == |
||
See [[C]]. |
|||
=== References === |
|||
* [http://www.acm.uiuc.edu/webmonkeys/book/c_guide/ The C Library Reference Guide] |
|||
* [http://gcc.gnu.org/onlinedocs/cpp/index.html C Preprocessor reference] |
|||
* manpage <tt>manpages-dev</tt> |
|||
* manpage <tt>manpages-posix-dev</tt> |
|||
<source lang="bash"> |
|||
sudo apt-get install manpages-dev manpages-posix-dev |
|||
</source> |
|||
=== Tips === |
|||
==== Variadic Macros ==== |
|||
See [http://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html#Variadic-Macros reference here]. |
|||
<source lang="c"> |
|||
#define eprintf(...) fprintf (stderr, __VA_ARGS__) |
|||
/* eprintf ("%s:%d: ", input_file, lineno) |
|||
==> fprintf (stderr, "%s:%d: ", input_file, lineno) */ |
|||
#define eprintf(args...) fprintf (stderr, args) |
|||
#define eprintf(format, ...) fprintf (stderr, format, __VA_ARGS__) |
|||
</source> |
|||
An handy macro hack that counts the number of parameters passed before expansion (See [http://en.wikipedia.org/wiki/Variadic_macro] and [http://groups.google.com/group/comp.std.c/browse_thread/thread/77ee8c8f92e4a3fb/346fc464319b1ee5]): |
|||
<source lang="c"> |
|||
/* The PP_NARG macro returns the number of arguments that have been |
|||
* passed to it. This compensates for lack of __VA_NARGS__. |
|||
* Macros written by Laurent Deniau See http://en.wikipedia.org/wiki/Variadic_macro. |
|||
*/ |
|||
#define PP_NARG(...) \ |
|||
PP_NARG_(__VA_ARGS__,PP_RSEQ_N()) |
|||
#define PP_NARG_(...) \ |
|||
PP_ARG_N(__VA_ARGS__) |
|||
#define PP_ARG_N( \ |
|||
_1, _2, _3, _4, _5, _6, _7, _8, _9,_10, \ |
|||
_11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \ |
|||
_21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \ |
|||
_31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \ |
|||
_41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \ |
|||
_51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \ |
|||
_61,_62,_63,N,...) N |
|||
#define PP_RSEQ_N() \ |
|||
63,62,61,60, \ |
|||
59,58,57,56,55,54,53,52,51,50, \ |
|||
49,48,47,46,45,44,43,42,41,40, \ |
|||
39,38,37,36,35,34,33,32,31,30, \ |
|||
29,28,27,26,25,24,23,22,21,20, \ |
|||
19,18,17,16,15,14,13,12,11,10, \ |
|||
9,8,7,6,5,4,3,2,1,0 |
|||
/* Some test cases */ |
|||
PP_NARG(A) -> 1 |
|||
PP_NARG(A,B) -> 2 |
|||
PP_NARG(A,B,C) -> 3 |
|||
PP_NARG(A,B,C,D) -> 4 |
|||
PP_NARG(A,B,C,D,E) -> 5 |
|||
PP_NARG(1,2,3,4,5,6,7,8,9,0, |
|||
1,2,3,4,5,6,7,8,9,0, |
|||
1,2,3,4,5,6,7,8,9,0, |
|||
1,2,3,4,5,6,7,8,9,0, |
|||
1,2,3,4,5,6,7,8,9,0, |
|||
1,2,3,4,5,6,7,8,9,0, |
|||
1,2,3) -> 63 |
|||
</source> |
|||
==== Temporary variable names for Macro ==== |
|||
<source lang="c"> |
|||
/* UNIQ(x) creates a unique variable name that depends on the current source line as returned by __LINE__. We need |
|||
Several intermediate macros because identifier are not expanded in macro if they are used along with # or ## in |
|||
macro definition. |
|||
Example: #define SCAN_MY(var,n) {int UNIQ(x); for(UNIQ(x)=0; UNIQ(x)<n; ++UNIQ(x)) printf(var[UNIQ(x)]);} |
|||
*/ |
|||
#define UNIQ__(x,y) x ## y |
|||
#define UNIQ_(x,y) UNIQ__(x,y) |
|||
#define UNIQ(x) UNIQ_(x,__LINE__) |
|||
</source> |
|||
== C++ == |
== C++ == |
||