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- You can alter the source line number and filename by writing a #line directive. The #line directive sets the value for the line that immediately follows the directive in the source file. The translator uses the line number and filename to determine the values of the predefined macros __FILE__ and __LINE__.
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Dec 1, 2022 · This directive is used by some automatic code generation tools which produce C++ source files from a file written in another language. In that case, #line directives may be inserted in the generated C++ file referencing line numbers and the file name of the original (human-editable) source file.
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In that case, #line directives may be inserted in the...
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Jan 21, 2009 · You use #include "yourfile.h" if yourfile.h is in the current working directory and #include <yourfile.h> if the path to yourfile.h file was included in the C++ include directories (somewhere in configuration, example: c:\mylib\yourfile.h, the path c:\mylib\ has to be specified as an include directory) Also you can include .cpp and .hpp (h plus ...
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The #line directive tells the preprocessor to set the compiler's reported values for the line number and filename to a given line number and filename.
The compiler uses the line number and optional filename to refer to errors that it finds during compilation. The line number usually refers to the current input line, and the filename refers to the current input file. The line number is incremented after each line is processed.
The digit-sequence value can be any integer constant within the range from 0 to 2147483647, inclusive. Macro replacement can be used on the preprocessing tokens, but the result must evaluate to the correct syntax. The filename can be any combination of characters and must be enclosed in double quotation marks (" "). If filename is omitted, the previous filename remains unchanged.
You can alter the source line number and filename by writing a #line directive. The #line directive sets the value for the line that immediately follows the directive in the source file. The translator uses the line number and filename to determine the values of the predefined macros __FILE__ and __LINE__. You can use these macros to insert self-descriptive error messages into the program text. For more information on these predefined macros, see Predefined macros.
The __FILE__ macro expands to a string whose contents are the filename, surrounded by double quotation marks (" ").
The following examples illustrate #line and the __LINE__ and __FILE__ macros.
In the first example, the line number is set to 10, then to 20, and the filename is changed to hello.cpp. In this example, the macro ASSERT uses the predefined macros __LINE__ and __FILE__ to print an error message about the source file if a given assertion isn't true.
This directive is used by some automatic code generation tools which produce C++ source files from a file written in another language. In that case, #line directives may be inserted in the generated C++ file referencing line numbers and the file name of the original (human-editable) source file.
bison or any such program can arrange this by writing ‘ #line ’ directives into the output file. ‘ #line ’ is a directive that specifies the original line number and source file name for subsequent input in the current preprocessor input file. ‘ #line ’ has three variants: #line linenum.
‘#line’ is a directive that specifies the original line number and source file name for subsequent input in the current preprocessor input file. ‘#line’ has three variants: #line linenum linenum is a non-negative decimal integer constant.
May 18, 2020 · Within C++ the pound symbol or # as the first character of a line indicates that the next word is a directive (or command word) to be evaluated. The two most common compiler directives are: include – with the item following include being the name of a file that is to be inserted at that place in the file.
