In the C++11 standard, several C99 preprocessor features are adopted to provide a common preprocessor interface for C and C++ compilers. This eases porting C source files to the C++ compiler and eliminates some subtle semantic differences that exist between the old C and C++ preprocessors, thus avoiding preprocessor compatibility issues or diverging preprocessor behaviors.
In the C89, C++98, and C++03 preprocessors, integer literals that have int or unsigned int type are widened to long or unsigned long. However, in the C99 and C++11 preprocessors, all signed and unsigned integer types (character types included) are widened to long long or unsigned long long under normal circumstances in XL C/C++.
If this feature is enabled, and both -qnolonglong and -qlanglvl=noc99longlong are set in either -q32 or -q64 modes, the preprocessor still uses long long or unsigned long long representations for all integral and character literals in preprocessor controlling expressions.
#if L'\x0' - L'\x1' < 0
#error non-C++11 preprocessor arithmetic.
#else
#error C++11 preprocessor arithmetic! L'\x0' and L'\x1' are widened to\
unsigned long long
#endif #if ~0ull == 0u + ~0u
#error C++11 preprocessor arithmetic! 0u has the same representation as 0ull,\
hence ~0ull == 0u + ~0u
#else
#error non-C++11 preprocessor arithmetic. 0ul does not have the same \
representation as 0ull, hence ~0ull != 0u + ~0u
#endifIf this feature is disabled and -qwarn0x is set, the C++11 preprocessor evaluates the controlling expressions in the #if and #elif directives, and compares the evaluation results against that of the non-C++11 preprocessor. If they are different, the compiler warns you that the preprocessor controlling expression evaluates differently between C++11 and non-C++11 language levels.
#include <wchar.h>
#include <stdio.h>
int main()
{
wprintf(L"Guess what? %ls\n", "I can now concate" L"nate regular strings\
and wide strings!");
printf("Guess what? %ls\n", L"I can now concate" "nate strings\
this way too!");
}Guess what? I can now concatenate regular strings and wide strings!
Guess what? I can now concatenate strings this way too!//inc.C
#include "0x/mylib.h"
int main()
{
return 0;
}"inc.C", line 1.10: 1540-0893 (W) The header file name "0x/mylib.h"
in #include directive shall not start with a digit.#line 1000000 //Valid in C++11, but invalid in C++98
int main()
{
return 0;
} //w.C
//With -qnodollar, '$' is not part of the macro name,
//thus it begins the replacement list
#define A$B c
#define STR2( x ) # x
#define STR( x ) STR2( x )
char x[] = STR( A$B ); "w.C", line 1.10: 1540-0891 (W) Missing white space between
the identifier "A" and the replacement list.#pragma comment(copyright, "IBM 2010")
_Pragma("comment(copyright, \"IBM 2010\")")_Pragma("comment(copyright, \"IBM 2010\")")
int main()
{
return 0;
}#define debug(...) fprintf(stderr, __VA_ARGS__)
#define showlist(...) puts(#__VA_ARGS__)
#define report(test, ...) ((test)?puts(#test): printf(__VA_ARGS__))
debug("Flag");
debug("X = %d\n", x);
showlist(The first, second, and third items.);
report(x>y, "x is %d but y is %d", x, y); fprintf(stderr, "Flag");
fprintf(stderr, "X = %d\n", x);
puts("The first, second, and third items.");
((x>y)?puts("x>y"): printf("x is %d but y is %d", x, y));