Re: "PORTING" C > weird char array values displayed in watch windo
Robby <Robby@discussions.microsoft.com> wrote:
"Igor Tandetnik" wrote:
Within set_spi_flash_buffer, spiFLASH_BUFFER refers to the
function's parameter, not to the global variable. And since the
parameter is declared without array size, the debugger doesn't know
how many elements you expect it to display.
ah yes, hum! I don't know why the hell I was passing the array while
it was even declared global *and get this* it always worked in the
other bloody old compiler like as if all of this was normal ......
It works in VC, too. It is legal to name a parameter, or a local =
variable, the same as a global variable. It's just confusing - mainly to =
yourself, because you had this unreasonable expectation that the =
parameter _is_ the same as the global variable just because it has the =
same name. Consider:
char x = 'x';
char y = 'y';
void f(char x) {
// x here is unrelated to the global variable named x.
printf("%c\n", x);
}
int main() {
f(y); // prints "y"
return 0;
}
unsigned char spiFLASH_BUFFER[88];
void set_buffer()
{
int r=0;
for(r=0;r<44;r++)
spiFLASH_BUFFER[r]= 0;
for(r=44;r<87;r++)
spiFLASH_BUFFER[r]= 255;
Did you mean not to assign to spiFLASH_BUFFER[87]?
However, sometimes in header files that others wrote, I sometimes see
multiple inclusion guards in the header files. This obviously tells
me that depending on another defined variable, we would allow
different inclusions. But why would people do this?
#ifdef et al is not just use for include guards. It's a general purpose =
mechanism for conditional compilation. Include guards is just one =
particular application of this general technique:
http://en.wikipedia.org/wiki/C_preprocessor#Conditional_compilation
For example, imagine that you are trying to write code that would =
compile both on MSVC and on your other compiler where int is 8 bit. =
Suppose you need an integer type that is always 8 bit regardless of =
which compiler you are targeting. You can do this:
#if defined (MSVC)
typedef int int8;
#elif defined(MY_OTHER_COMPILER)
typedef signed char int8;
#else
#error Define the compiler you want to build for.
#endif
Now in your project settings (or makefiles, or whatever you use to drive =
the build) you can define an appropriate macro, and in your code just =
use int8 knowing that it will be defined appropriately.
--
With best wishes,
Igor Tandetnik
With sufficient thrust, pigs fly just fine. However, this is not =
necessarily a good idea. It is hard to be sure where they are going to =
land, and it could be dangerous sitting under them as they fly overhead. =
-- RFC 1925