stringizing a hex value in the preprocessor

[Henry Townsend]

Consider the little program below. It simply attempts to determine what
version of what compiler it was built with via documented preprocessor
macros and print out the result. When the compiler is gcc it works fine,
because __VERSION__ is supplied as a string. But identifying the Sun
compiler is harder because it provides __SUNPRO_C as a numerical value
(equal in my case to 0x580). My attempt to stringify it produces an error:

% cc -g -o foo foo.c
"foo.c", line 13: invalid source character: '#'
"foo.c", line 13: syntax error before or at: 0x580
cc: acomp failed for foo.c

Is there a way to do this?

Thanks,
HT

--------------------------------------------------------------
#include <stdio.h>

#if defined(__GNUC__)
#define COMPILER_STRING "gcc " __VERSION__
#elif defined(__SUNPRO_C)
#define COMPILER_STRING "SunStudio " #__SUNPRO_C
#else
#define COMPILER_STRING "unknown compiler/version"
#endif

int main(void)
{
printf("Compiled with %s\n", COMPILER_STRING);
return 0;
}

 

[Suman]

Consider the little program below. It simply attempts to determine what
version of what compiler it was built with via documented preprocessor
macros and print out the result. When the compiler is gcc it works fine,
because __VERSION__ is supplied as a string. But identifying the Sun
compiler is harder because it provides __SUNPRO_C as a numerical value
(equal in my case to 0x580). My attempt to stringify it produces an error:

Here's my try:

#include <stdio.h>

#define str(x) #x
#define xstr(x) str(x)
#define paste(x, y) x ## y

#define __SUNPRO_C 0x580
#if defined(__IGNUC__)
#define COMPILER_STRING "gcc " __VERSION__
#elif defined(__SUNPRO_C)
#define COMPILER_STRING xstr(paste(SunStudio, xstr(__SUNPRO_C)))
#else
#define COMPILER_STRING "unknown compiler/version"
#endif

int main(void)
{
printf("Compiled with %s\n", COMPILER_STRING);
return 0;
}

and this was compiled with gcc -std=c99 -Wall.

 

[Suman]

Here's my try:

a tad improved:
--------------------------------------><----------------------------------------------------------------
#include <stdio.h>

#define str(x) #x
#define xstr(x) str(x)
#define paste(x, y) x ## y

#define __SUNPRO_C 0x580
#if defined(__IGNUC__)
#define COMPILER_STRING "gcc " __VERSION__
#elif defined(__SUNPRO_C)
#define COMPILER_STRING xstr(SunStudio xstr(__SUNPRO_C))
#else
#define COMPILER_STRING "unknown compiler/version"
#endif

int main(void)
{
printf("Compiled with %s\n", COMPILER_STRING);
return 0;
}
--------------------------------------><----------------------------------------------------------------
gcc -std=c99 -Wall -pedantic -ansi. And, excuse the ignominious
__IGNU__.
I don't have a Sun compiler to play with

HTH

 

[Henry Townsend]

Here's my try:

a tad improved:
[snip]

Yes, that works. Actually it prints:

Compiled with SunStudio "0x580"

and a tweak I made to use the line:

#define COMPILER_STRING "SunStudio " ## xstr(__SUNPRO_C)

removes the quotes to give:

Compiled with SunStudio 0x580

Which is what I was looking for. Thanks!

HT

 

[Raghu]

Here is My try :

#include <stdio.h>

#define str(x) #x
#define paste(x,y) x##y
#define Mystr(x) str(x)


#define __SUNPRO_C 0x580

#if defined(__IGNUC__)

#define COMPILER_STRING "gcc " __VERSION__

#elif defined(__SUNPRO_C)

#define COMPILER_STRING paste("SunStudio",Mystr(__SUNPRO_C))

#else

#define COMPILER_STRING "unknown compiler/version"

#endif

int main(void)
{
printf("Compiled with %s\n", COMPILER_STRING);
return 0;
}


-- Raghu.

Here's my try:

a tad improved:
[snip]

Yes, that works. Actually it prints:

Compiled with SunStudio "0x580"

and a tweak I made to use the line:

#define COMPILER_STRING "SunStudio " ## xstr(__SUNPRO_C)

removes the quotes to give:

Compiled with SunStudio 0x580

Which is what I was looking for. Thanks!

HT

 

[Hubble]

Except that I would not use small letters for macros. Or did I miss
something? The solution is good but hard to read for me.

Hubble

 

[Maxim Yegorushkin]

Consider the little program below. It simply attempts to determine what
version of what compiler it was built with via documented preprocessor
macros and print out the result. When the compiler is gcc it works fine,
because __VERSION__ is supplied as a string. But identifying the Sun
compiler is harder because it provides __SUNPRO_C as a numerical value
(equal in my case to 0x580). My attempt to stringify it produces an error:

Why not just use a simple shell script invoked by makefile to do just
that?

$ cat build_string
#! /bin/bash

echo "namespace $1 { "
echo "extern char const build_string[] = "
echo \"$(date -u +"%F %T UTC") \"
echo \"$(g++ --version | head -n 1)\"
echo ";"
echo "}"

bash-3.00$ cat Makefile

....
all: app
app: dirs build_string $(app_obj)
$(CXX) -o $(bin_dir)app $(app_obj) $(LDFLAGS)
....
..PHONY : dirs clean build_string install
build_string:
./build_string app > $(src_dir)build_string.cpp
....

 

[Keith Thompson]

Except that I would not use small letters for macros. Or did I miss
something? The solution is good but hard to read for me.

What solution?

Please read <http://cfaj.freeshell.org/google/>.

 

[Hubble]

What solution

Please read <http://cfaj.freeshell.org/google/>.

Sorry for using google:

#define str(x) #x
#define xstr(x) str(x)
#define paste(x, y) x ## y

I would not use small letters for macros. Or did I miss
something? These macros is good but hard to read for me.

Hubble

 

[pete]

Hubble wrote:

I would not use small letters for macros. Or did I miss
something? These macros is good but hard to read for me.

The first two of those macros are copied from the C standard.
That makes it easy to look them up in the standard
if you want to see what the standard has to say about them.
Otherwise, neither would I write them that way.

 

[Jordan Abel]

#ifdef __STDC__

#define str(x) #x
#define paste(x, y) x ## y

#else
#define str(x) "x"
#define paste(x) x/**/y
#endif

 

[pete]

The first two of those macros are copied from the C standard.
That makes it easy to look them up in the standard
if you want to see what the standard has to say about them.
Otherwise, neither would I write them that way.

I suppose they wouldn't be that difficult to look up
if they were in caps and you knew they were in the standard.
There's a couple of things
that I copy from the C standard in my code.

For example

int main(int argc, char *argv[])

even though

int main(int argc, char **argv)

is really my prefered style.

 

[Keith Thompson]

Sorry for using google:

[snip]

No need to apologize; using google is perfectly acceptable as long as
you use it correctly. (Some people have killfiled everything posted
through groups.google.com, but that's their decision.)

 

[Suman]

The first two of those macros are copied from the C standard.
That makes it easy to look them up in the standard
if you want to see what the standard has to say about them.
Otherwise, neither would I write them that way.

Addendum:
The third, is a modified form of what you find in K&R 2:
#define paste(front, back) front ## back

 

[pete]

Addendum:
The third, is a modified form of what you find in K&R 2:
#define paste(front, back) front ## back

That's good enough for me.

It might be worth keeping in mind
that there's a few deviations here and there in standard C,
from what's generally considered good style.
FILE is a typedef, stdout is a macro.