Using __LINE__ as a string

[Paul Shipley]

Hi,

Does anyone know a way of converting the __LINE__ macro to a string at
compile time? The reason I ask it because I want to put some debug
information in to tell me if memory is not being allocated. For
example, this function will return the status of my system:

static char* get_status (void)
{
char* str_ptr;
str_ptr = mem_alloc( SIZE_OF_TEXT );

if( NULL == str_ptr )
{
str_ptr = "Out of memory in " __FILE__ " at " __LINE__ "\n";
}
else
{
str_ptr = /* blah blah blah... */
}
return( str_ptr);
}

Of course this code won't work, because __LINE__ is an integer, not a
string. Also, I can't resort to something like printf( "%u \n",
__LINE__ ) because in this case the output might not (and probably
won't) be going to stdout. Also, sprintf can't be used because there
is no memory available to sprintf to.

Any suggestions on how to convert __LINE__ to a string at compile time
will be most appreciated.

Thanks,
Paul.

[Joona I Palaste]

Paul Shipley <pa**********@s evcon.com> scribbled the following:

Hi, Does anyone know a way of converting the __LINE__ macro to a string at
compile time? The reason I ask it because I want to put some debug
information in to tell me if memory is not being allocated. For
example, this function will return the status of my system: static char* get_status (void)
{
char* str_ptr;
str_ptr = mem_alloc( SIZE_OF_TEXT ); if( NULL == str_ptr )
{
str_ptr = "Out of memory in " __FILE__ " at " __LINE__ "\n";
sprintf(str_ptr , "Out of memory in %s at %d\n", __FILE__, __LINE__);
}
else
{
str_ptr = /* blah blah blah... */
}
return( str_ptr);
}

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"I will never display my bum in public again."
- Homer Simpson

[Hallvard B Furuseth]

Paul Shipley wrote:

Hi,

Does anyone know a way of converting the __LINE__ macro to a string at
compile time? (...)
#define NOMEM() NOMEM__1(__LINE __)
#define NOMEM__1(li) NOMEM__2(li)
#define NOMEM__2(li) "Out of memory in " __FILE__ " at " #li "\n"

'#li' converts the _unexpanded_ argument to a string. That's why
three macros are needed: This
#define NOMEM__1(li) "Out of memory in " __FILE__ " at " #li "\n"
would produce "Out of memory in " "foo.c" " at " "__LINE__" "\n"
static char* get_status (void)
{
char* str_ptr;
str_ptr = mem_alloc( SIZE_OF_TEXT );

if( NULL == str_ptr )
{
str_ptr = "Out of memory in " __FILE__ " at " __LINE__ "\n";
str_ptr = NOMEM()
}
else
{
str_ptr = /* blah blah blah... */
}
return( str_ptr);
}

However, this program has a bug. How will the caller know whether
or not to free the returned memory? It can return either memory
from mem_alloc() or a static string.

--
Hallvard

[Hallvard B Furuseth]

Joona I Palaste wrote:

str_ptr = mem_alloc( SIZE_OF_TEXT );
if( NULL == str_ptr )
{
str_ptr = "Out of memory in " __FILE__ " at " __LINE__ "\n";

sprintf(str_ptr , "Out of memory in %s at %d\n", __FILE__, __LINE__);

Not a good idea when str_ptr == NULL.
Besides, we don't know if SIZE_OF_TEXT is big enough.

--
Hallvard

[Mathew Hendry]

On 21 Oct 2003 03:46:59 -0700, pa**********@se vcon.com (Paul Shipley) wrote:

Any suggestions on how to convert __LINE__ to a string at compile time
will be most appreciated.

D:\source\clc>c at 031021_1.c
#include <stdio.h>

#define STRX(x) #x
#define STR(x) STRX(x)

int main(void)
{
const char *line = STR(__LINE__);
printf("line == %s\n", line);
return 0;
}

D:\source\clc>0 31021_1
line == 8

You must go through two macros to force expansion of __LINE__, otherwise

line == __LINE__

would be printed. :)

-- Mat.

[Joona I Palaste]

Hallvard B Furuseth <h.b.furuseth(n ospam)@usit.uio (nospam).no> scribbled the following:

Joona I Palaste wrote:

str_ptr = mem_alloc( SIZE_OF_TEXT );
if( NULL == str_ptr )
{
str_ptr = "Out of memory in " __FILE__ " at " __LINE__ "\n";
sprintf(str_ptr , "Out of memory in %s at %d\n", __FILE__, __LINE__);

Not a good idea when str_ptr == NULL.
Besides, we don't know if SIZE_OF_TEXT is big enough.

Whoops. Misread == as !=. Thanks for the correction. Well, if we assume
that SIZE_OF_TEXT is absolute bloody big, then we could malloc() a
smaller amount here and sprintf() into it.
After all, there has to be enough memory to hold the "Out of memory"
message somewhere. If not, we're screwed even with the original
solution.

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"I will never display my bum in public again."
- Homer Simpson

[Dan Pop]

In <bn**********@o ravannahka.hels inki.fi> Joona I Palaste <pa*****@cc.hel sinki.fi> writes:

Hallvard B Furuseth <h.b.furuseth(n ospam)@usit.uio (nospam).no> scribbled the following:

Joona I Palaste wrote:

str_ptr = mem_alloc( SIZE_OF_TEXT );
if( NULL == str_ptr )
{
str_ptr = "Out of memory in " __FILE__ " at " __LINE__ "\n";

sprintf(str_ptr , "Out of memory in %s at %d\n", __FILE__, __LINE__);

Not a good idea when str_ptr == NULL.
Besides, we don't know if SIZE_OF_TEXT is big enough.

Whoops. Misread == as !=. Thanks for the correction. Well, if we assume
that SIZE_OF_TEXT is absolute bloody big, then we could malloc() a
smaller amount here and sprintf() into it.
After all, there has to be enough memory to hold the "Out of memory"
message somewhere. If not, we're screwed even with the original
solution.

If not, one of two things will happen:

1. The program will fail to translate.

2. The program will fail to load.

In either case, the program cannot be executed. That's the big advantage
of static memory allocation: you don't spend hours and hours of execution
time only to be told that the program cannot allocate some memory it
needs in order to continue to execute.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Dan Pop]

In <5a************ **************@ posting.google. com> pa**********@se vcon.com (Paul Shipley) writes:

Any suggestions on how to convert __LINE__ to a string at compile time
will be most appreciated.

Ever considered reading the FAQ *before* posting?

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Tristan Miller]

Greetings.

In article <bn**********@o ravannahka.hels inki.fi>, Joona I Palaste wrote:

sprintf(str_ptr , "Out of memory in %s at %d\n", __FILE__, __LINE__);

Complicated. You will need to calculate a base-10 logarithm and one or more
strlen()s to make sure that the str_ptr has enough memory allocated.
Unless you really need the string in dynamic memory, it's better to use the
preprocessor to generate a constant string on the fly.

Regards,
Tristan

--
_
_V.-o Tristan Miller [en,(fr,de,ia)] >< Space is limited
/ |`-' -=-=-=-=-=-=-=-=-=-=-=-=-=-=-= <> In a haiku, so it's hard
(7_\\ http://www.nothingisreal.com/ >< To finish what you

[E. Robert Tisdale]

Dan Pop wrote:

Paul Shipley writes:

Any suggestions on how to convert __LINE__ to a string at compile time
will be most appreciated.

Ever considered reading the FAQ *before* posting?

Exactly which FAQ answers this question?