C Standard predefined macros

The ansi c standard has several predefined macros: __file _ date _ time ___ _ line _.

_ Line __: inSource codeInsert Current SourceCodeRow number;

_ File __: insert the name of the current source file into the source file;

_ Date __: Insert the current compilation date into the source file

_ Time __: Insert the current compilation time into the source file;

_ Stdc __: when requiredProgramWhen the ansi c standard is strictly followed, this identifier is assigned a value of 1;

_ Cplusplus: This identifier is defined when a C ++ program is compiled.

These macros are useful ~~~~~~~~

When debugging a program or compiling a program, __line _ is useful. It can be used to print the line numbers of logical errors ~~~~~~~, Example:

Switch (X)

{

Case 1:

....;

Break;

 

Case 2:

.....;

Break;

 

Default:

Printf ("logic erro line number % d! /N ",__ line __);

Break;

}

Another example is to use _ date _ and _ time _ to insert the Compilation Time.

Code:

Void print_version_info (void)

{

Printf ("date compiled: % s/n" ,__ date __);

Printf ("timecompiled: % s/n" ,__ time __);

}

Output Format: Mm dd yy and HH: mm: SS

 

 

 

 

 

 

 

 

 

Function: It is useful when debugging programs for macros such as _ file __,__ line __,__ func, because you can easily know which file the program is running
Row, which function is used.

The following example prints the predefined macros.

_ Date __,__ file __,__ line __,__ time __,__ function __
Some predefined macros are specified in the C standard and are often used in programming. The following table lists some predefined macros that are frequently used.

_ Date _ % S _
Date of preprocessing (string text in the form of "Mmm dd YYYY)

_ File _ % s
String text representing the current source code file name

_ Line __
% D
An integer constant representing the row number in the current source code.

_ Time _ % s
Source File Compilation Time, in the format of "HH: mm: SS"

_ Function _ (_ FUNC _) % s
Current function name

_ Pretty_function __
% S

The name of the current function, including the return type and parameter type.

For example: printf ("_ pretty_function __: % s/n", _ pretty_function __);

Output :__ pretty_function __: int main (INT, char **)

 

# Include <stdio. h>
# Include <stdlib. h>
Void why_me ();
Int main ()
{
Printf ("
File is % S./N ", _ file __);
Printf ("
Date is % S./N ", _ date __);
Printf ("
Time is % S./N ", _ time __);
Printf (
"This is line % d./N", _ line __);
Printf (
"This function is % S./N", _ function __);

Why_me ();
Return
0;
}

Void why_me ()
{
Printf (
"This function is % s/n", _ FUNC __);
Printf ("
File is % S./N ", _ file __);
Printf (
"This is line % d./N", _ line __);
}