Filename and line information

Changes the current line number and file name in the preprocessor.

Syntax

Explanation

Any preprocessing tokens (macro constants or expressions) are permitted as arguments to #line

lineno must be a sequence of at least one decimal digit (the program is ill-formed, otherwise) and is always interpreted as decimal (even if it starts with 0).

If lineno is 0 or greater than 32767(until C99) 2147483647(since C99)

Notes

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

The line number following the directive #line __LINE__ is unspecified (there are two possible values that __LINE__ can expand to in this case: number of endlines seen so far, or number of endlines seen so far plus the endline that ends the #line directive). This is the result of DR 464

Example

#include <assert.h>
#define FNAME "test.c"
int main(void)
{
#line 777 FNAME
        assert(2+2 == 5);
}

test: test.c:777: int main(): Assertion `2+2 == 5' failed.

References

See also