Macros

[Winbatch]

I have an exception class whose constructor takes in 3 parameters,
a string, an int, and a string.
The parameters represent a filename, a line number, and an error message
where the error occurred.

I call the function as follows

if ( whatever_problem)
throw MyException(__FILE__,__LINE__, "This was my problem");

This is all working fine, though it's getting annoying to have to type
__FILE__,__LINE__ every time. How do I write a macro that will put that in
its place so that I can do something like:

if ( whatever_problem)
throw MyException(ERROR_PARMS, "This was my problem");

[Rolf Magnus]

Winbatch wrote:

I have an exception class whose constructor takes in 3 parameters,
a string, an int, and a string.
The parameters represent a filename, a line number, and an error message
where the error occurred.

I call the function as follows

if ( whatever_problem)
throw MyException(__FILE__,__LINE__, "This was my problem");

This is all working fine, though it's getting annoying to have to type
__FILE__,__LINE__ every time. How do I write a macro that will put that
in its place so that I can do something like:

if ( whatever_problem)
throw MyException(ERROR_PARMS, "This was my problem");

Uhm,

#define ERROR_PARMS __FILE__,__LINE__

?

[Phlip]

Winbatch wrote:

if ( whatever_problem)
throw MyException(__FILE__,__LINE__, "This was my problem");

This is all working fine, though it's getting annoying to have to type
__FILE__,__LINE__ every time. How do I write a macro that will put that
in its place so that I can do something like:

Off the top of my head, might have a syntax error,

#define CHECK(q) \
do{ if (!(q)) \
throw MyException(__FILE__,__LINE__, #q "failed"); } \
while(false)

If you are going to write a macro, then really write it. Put all the
duplicated code you can into it.

That advice risks the spectre of "macro abuse", so follow this checklist.
Does my macro:

- use conditional compilation
- stringerize
- paste tokens

My macro follows the first two (__FILE__ & __LINE__ are a kind of
conditional compilation, because their condition changes all the time, and
#q is stringerization).

To reduce the macro abuse further, put the logic into a function and call
that:

void check(bool q, char const * strQ, char const * file, unsigned long line)
{
if (!q)
throw MyException(file, line, strQ);
}

#define CHECK(q) \
check(q, #q "failed", __FILE__,__LINE__)

--
Phlip
http://c2.com/cgi/wiki?ZeekLand <-- NOT a blog!!!

[Winbatch]

"Rolf Magnus" <ra******@t-online.de> wrote in message
news:e3*************@news.t-online.com...

Winbatch wrote:

I have an exception class whose constructor takes in 3 parameters,
a string, an int, and a string.
The parameters represent a filename, a line number, and an error message
where the error occurred.

I call the function as follows

if ( whatever_problem)
throw MyException(__FILE__,__LINE__, "This was my problem");

This is all working fine, though it's getting annoying to have to type
__FILE__,__LINE__ every time. How do I write a macro that will put that
in its place so that I can do something like:

if ( whatever_problem)
throw MyException(ERROR_PARMS, "This was my problem");

Uhm,

#define ERROR_PARMS __FILE__,__LINE__

?

Sorry, didn't realize it was that simple. I must have put a space or
something in between or typed something funny as it had given me a compiler
error. (Don't remember what it said. In any case, it works. Thanks)