Difference between byte and char in C

Question

I am wondering why I can't compile an example from book. I simplify the example here to avoid posting example from a copyrighted book.

#include <stdio.h>

BYTE *data = "data";

int main()
{
     printf("%s", data);
     return 0;
}

When compile with g++, i get error,

error: invalid conversion from 'const char*' to 'BYTE*'

The program works by simply replacing BYTE with char, but I must be doing something wrong since the example comes from a book.

Please help pointing out the problem. Thanks.

The question is tagged C, but you say that you are using g++ which is a C++ compiler. Which language are you using? — Lara Bailey
– Lara Bailey, Commented Oct 20, 2009 at 6:15
I'm using the C part of C++ . Isnt C++ backward compatible with C, so if I'm only using the C part, it doesn't matter g++ or gcc? — idazuwaika
– idazuwaika, Commented Oct 20, 2009 at 8:34
C++ isn't a quite a superset of C(a few things are missing). However, it doesn't matter for this question. — rsaxvc
– rsaxvc, Commented Apr 18, 2015 at 22:33

Jonathan Leffler · Accepted Answer · 2009-10-20 06:24:10Z

47

BYTE isn't a part of the C language or C standard library so it is totally system dependent on whether it is defined after including just the standard stdio.h header file.

On many systems that do define a BYTE macro, it is often an unsigned char. Converting from a const char* to an unsigned char* would require an explicit cast.

edited Oct 20, 2009 at 6:24

Jonathan Leffler

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answered Oct 20, 2009 at 6:08

Lara Bailey

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4 Comments

ChrisBD Over a year ago

Yep - there's your answer idazwaika - custom datatype definitions can cause trouble.

Tim Kryger Over a year ago

You may also want to note that the C standard allows the compiler to make char to be either signed char or unsigned char which can lead to some unexpected results.

idazuwaika Over a year ago

Thanks. Looks like I have to hunt for the definition of BYTE macro. Is there a way I can get the output of C pre-processor where macros are translated already?

eyalm Over a year ago

idazuwaika: Use gcc -E (Preprocess only; do not compile, assemble or link)

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