How can I compile a file with different constants?

[Valentin Tihomirov]

I have a .c file with a general code. It can be compiled with different
constants for different applications. For example

char a[BYTE_SIZE];

where BYTE_SIZE is a constant defined in an external (.h?) file.

[osmium]

Valentin Tihomirov writes:

I have a .c file with a general code. It can be compiled with different
constants for different applications. For example

char a[BYTE_SIZE];

where BYTE_SIZE is a constant defined in an external (.h?) file.

Perhaps you want to know about the preprocessor? You can use #define and
control it with #if.

[Martin Ambuhl]

Valentin Tihomirov wrote:

I have a .c file with a general code. It can be compiled with different
constants for different applications. For example

char a[BYTE_SIZE];

where BYTE_SIZE is a constant defined in an external (.h?) file.

Use CHAR_BIT from <limits.h>.
But note that the "size" of a byte as given by sizeof(char) is always 1.
--
Martin Ambuhl

[Ben Pfaff]

Martin Ambuhl <ma*****@earthlink.net> writes:

Valentin Tihomirov wrote:

I have a .c file with a general code. It can be compiled with different
constants for different applications. For example
char a[BYTE_SIZE];
where BYTE_SIZE is a constant defined in an external (.h?) file.

Use CHAR_BIT from <limits.h>.
But note that the "size" of a byte as given by sizeof(char) is always 1.

I don't think you're answering the OP's question.
--
"Your correction is 100% correct and 0% helpful. Well done!"
--Richard Heathfield

[Rouben Rostamian]

In article <3f**********@news.estpak.ee>,
Valentin Tihomirov <va******@abelectron.com> wrote:

I have a .c file with a general code. It can be compiled with different
constants for different applications. For example

char a[BYTE_SIZE];

where BYTE_SIZE is a constant defined in an external (.h?) file.

If BYTE_SIZE is defined somewhere, well, there is not much you
can do about it. That's that.

If BYTE_SIZE is undefined, then see if your compiler supports a
-D flag. For instance, with gcc you may do:

gcc -DBYTE_SIZE=23 prog.c

--
Rouben Rostamian <ro*******@umbc.edu>

[Dan Pop]

In <3f**********@news.estpak.ee> "Valentin Tihomirov" <va******@abelectron.com> writes:

I have a .c file with a general code. It can be compiled with different
constants for different applications. For example

char a[BYTE_SIZE];

where BYTE_SIZE is a constant defined in an external (.h?) file.

If BYTE_SIZE is defined in a header file, all you have to do is to
include that header before using the BYTE_SIZE macro.

Most compilers also allow you to define macros at compile time, e.g.
via compiler command line options.

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