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    05 junio

    gcc 中宏定义的问题

    如果在gcc/g++中使用-D参数预定义宏时，需要注意gcc/g++间各个参数的数据。-D参数一定要在-I、-L参数之前；而且最好靠前操作。
    -D参数可以预定定义的宏的长度不限，但是肯定也不能太长。
    ===================== Example======================
    例子如下：
    bash-2.03$ more elif.cpp
    #include <stdio.h>
    int main()
    {
    #ifdef MACRO1234567890
            printf(" DEBUG1 \n");
    #elif defined(DEBUGaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa2)
            printf(" DEBUG2 \n");
    #else
            printf(" DEUBG3 \n");
    #endif
            return 0;
    }
    bash-2.03$ gcc -DMACRO1234567890 elif.cpp -o elif
    bash-2.03$ ./elif
     DEBUG1
    bash-2.03$ gcc -DDEBUGaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa2 elif.cpp -o elif
    bash-2.03$ ./elif
     DEBUG2
    bash-2.03$ gcc elif.cpp -o elif
    bash-2.03$ ./elif
     DEUBG3
    23:01 | Agregar un comentario | Vínculo permanente | Agregar al blog | 技术

    算法应用的几个思考

    （1）对于任何一个优秀的算法，在某些条件下他的效率是很低，这是算法设计过程中难免的。所以要根据算法本身特点，设计使用算法的环境，使得该算法能够长期、大概率的运行于其效率最高的部分。这个是算法和算法应用的思考。
    （2）……
    15:24 | Agregar un comentario | Vínculo permanente | Agregar al blog | 技术
    02 junio

    C/C++ Predefined Macros

    The compiler recognizes 10 predefined ANSI C macros, and the Microsoft C++ implementation provides several more. These macros take no arguments and cannot be redefined. Their value, except for __LINE__ and __FILE__, must be constant throughout compilation. Some of the predefined macros listed below are defined with multiple values. See the following tables for more information.

    ANSI-Compliant Predefined Macros

    Macro Description
    __DATE__ The compilation date of the current source file. The date is a string literal of the form Mmm dd yyyy. The month name Mmm is the same as for dates generated by the library function asctime declared in TIME.H.
    __FILE__ The name of the current source file. __FILE__ expands to a string surrounded by double quotation marks.

    You can create your own wide string version of __FILE__ as follows:

    #include <stdio.h>
#define WIDEN2(x) L ## x
#define WIDEN(x) WIDEN2(x)
#define __WFILE__ WIDEN(__FILE__)
wchar_t *pwsz = __WFILE__;

int main()
{
}
    __LINE__ The line number in the current source file. The line number is a decimal integer constant. It can be altered with a #line directive.
    __STDC__ Indicates full conformance with the ANSI C standard. Defined as the integer constant 1 only if the /Za compiler option is given and you are not compiling C++ code; otherwise is undefined.
    __TIME__ The most recent compilation time of the current source file. The time is a string literal of the form hh:mm:ss.
    __TIMESTAMP__ The date and time of the last modification of the current source file, expressed as a string literal in the form Ddd Mmm Date hh:mm:ss yyyy, where Ddd is the abbreviated day of the week and Date is an integer from 1 to 31.

    Microsoft-Specific Predefined Macros

    Macro Description
    _ATL_VER Defines the ATL version.
    _CHAR_UNSIGNED Default char type is unsigned. Defined when /J is specified.
    __COUNTER__ Expands to an integer starting with 0 and incrementing by 1 every time it is used in a compiland. __COUNTER__ remembers its state when using precompiled headers. If the last __COUNTER__ value was 4 after building a precompiled header (PCH), it will start with 5 on each PCH use.

    __COUNTER__ lets you generate unique variable names. You can use token pasting with a prefix to make a unique name. For example:

    #include <stdio.h>
#define FUNC2(x,y) x##y
#define FUNC1(x,y) FUNC2(x,y)
#define FUNC(x) FUNC1(x,__COUNTER__)

int FUNC(my_unique_prefix);
int FUNC(my_unique_prefix);

int main() {
   my_unique_prefix0 = 0;
   printf("\n%d",my_unique_prefix0);
   my_unique_prefix0++;
   printf("\n%d",my_unique_prefix0);
}
    __cplusplus Defined for C++ programs only.
    _CPPLIB_VER Defined if you include any of the C++ Standard Library headers; reports which version of the Dinkumware header files are present.
    _CPPRTTI Defined for code compiled with /GR (Enable Run-Time Type Information).
    _CPPUNWIND Defined for code compiled with /GX (Enable Exception Handling).
    _DEBUG Defined when compiling with /LDd, /MDd, /MLd, and /MTd.
    _DLL Defined when /MD or /MDd (Multithread DLL) is specified.
    __FUNCDNAME__ Valid only within a function and returns the decorated name of the enclosing function (as a string). __FUNCDNAME__ is not expanded if you use the /EP or /P compiler option.
    __FUNCSIG__ Valid only within a function and returns the signature of the enclosing function (as a string). __FUNCSIG__ is not expanded if you use the /EP or /P compiler option.
    __FUNCTION__ Valid only within a function and returns the undecorated name of the enclosing function (as a string). __FUNCTION__ is not expanded if you use the /EP or /P compiler option.
    _M_ALPHA Defined for DEC ALPHA platforms. It is defined as 1 by the ALPHA compiler, and it is not defined if another compiler is used.
    _M_IX86 Defined for x86 processors. See Values for _M_IX86 for more details.
    _M_IA64 Defined for 64-bit processors.
    _M_MPPC Defined for Power Macintosh platforms (no longer supported).
    _M_MRX000 Defined for MIPS platforms (no longer supported).
    _M_PPC Defined for PowerPC platforms (no longer supported).
    _MANAGED Defined to be 1 when /clr is specified.
    _MFC_VER Defines the MFC version. For example, 0x0700 represents MFC version 7.
    _MSC_EXTENSIONS This macro is defined when compiling with the /Ze compiler option (the default). Its value, when defined, is 1.
    _MSC_VER Defines the major and minor versions of the compiler. For example, 1300 for Microsoft Visual C++ .NET. 1300 represents version 13 and no point release. This represents the fact that there have been a total of 13 releases of the compiler.

    If you type cl /? at the command line, you will see the full version for the compiler you are using.

    __MSVC_RUNTIME_CHECKS Defined when one of the /RTC compiler options is specified.
    _MT Defined when /MD or /MDd (Multithreaded DLL) or /MT or /MTd (Multithreaded) is specified.
    _WCHAR_T_DEFINED

    and

    _NATIVE_WCHAR_T_DEFINED

    		 Defined when wchar_t is defined. Typically, wchar_t is defined when you use /Zc:wchar_t or when typedef unsigned short wchar_t; is executed in code.
    _WIN32 Defined for applications for Win32 and Win64. Always defined.
    _WIN64 Defined for applications for Win64.
    _Wp64 Defined when specifying /Wp64.

    As shown in following table, the compiler generates a value for the preprocessor identifiers that reflect the processor option specified.

     
    15:10 | Agregar un comentario | Vínculo permanente | Agregar al blog | 技术