Problem with a pointer

[mauri1106]

Hi, I have a little problem with a pointer.

In my project is included an ".h" file with this declaration:

"#define pMDMA_D0_START_ ADDR ((void * volatile *)MDMA_D0_START _ADDR)"

If I assign a value (e.g. *pMDMA_S0_START _ADDR = 0x04000;) the
compiler give me these 2 warning:
".\init.c", line 105: cc0513: {D} warning: a value of type "int" cannot
be
assigned to an entity of type "void *"
*pMDMA_S0_START _ADDR = 0x04000;
^

".\init.c", line 105: cc0152: {D} warning: conversion of nonzero
integer to
pointer
*pMDMA_S0_START _ADDR = 0x04000;
^

Why appears these warnings?

thanks, Maurizio

[Ravi Uday]

mauri1106 wrote:

Hi, I have a little problem with a pointer.

In my project is included an ".h" file with this declaration:

"#define pMDMA_D0_START_ ADDR ((void * volatile *)MDMA_D0_START _ADDR)"

If I assign a value (e.g. *pMDMA_S0_START _ADDR = 0x04000;) the
How is pMDMA_S0_START_ ADDR defined ?
compiler give me these 2 warning:
".\init.c", line 105: cc0513: {D} warning: a value of type "int" cannot
be
assigned to an entity of type "void *"
*pMDMA_S0_START _ADDR = 0x04000;
^
Thats probably because your #define is pMDMA_D0_START_ ADDR
^^
and error you got points to *pMDMA_S0_START _ADDR
^^

Post the real code please !
One more suggestion is you could look at the pre-processor output
to see how your macro has expanded in the code.

- Ravi

".\init.c", line 105: cc0152: {D} warning: conversion of nonzero
integer to
pointer
*pMDMA_S0_START _ADDR = 0x04000;
^

Why appears these warnings?

thanks, Maurizio

[mauri1106]

I'm sorry, is correct with "S0" in assegnation!

[Flash Gordon]

mauri1106 wrote:

Hi, I have a little problem with a pointer.

In my project is included an ".h" file with this declaration:

"#define pMDMA_D0_START_ ADDR ((void * volatile *)MDMA_D0_START _ADDR)"
I assume that you also have something like the following in our header:
#define MDMA_DO_START_A DDR 0x12345678

In future, please provide a *complete* minimal example that shows the
problem (compilable, unless the problem is that it won't compiler).
If I assign a value (e.g. *pMDMA_S0_START _ADDR = 0x04000;) the
compiler give me these 2 warning:
".\init.c", line 105: cc0513: {D} warning: a value of type "int" cannot
be
assigned to an entity of type "void *"
*pMDMA_S0_START _ADDR = 0x04000;
That's simple. void* is a generic pointer type, so of course you can't
read or write through a void* pointer. You need to have a pointer to a
complete, known type, e.g. int or char.
".\init.c", line 105: cc0152: {D} warning: conversion of nonzero
integer to
pointer
That's simple as well. The only integer to pointer fully defined by the
C standard is that 0 converts to a null pointer. For the rest, it is
implementation defined with one possible definition being that there is
no integer type large enough to represent pointers.
*pMDMA_S0_START _ADDR = 0x04000;
^

Why appears these warnings?

Because you are writing terrible code. I'm guessing that you are trying
to access hardware directly, but depending on the OS you are using (if
you are using one) this may not be possible, but even if it is the
compiler needs to know the type of what it is trying to access.
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.

[mauri1106]

the correct assegantion is:

"#define pMDMA_S0_START_ ADDR ((void * volatile *)MDMA_S0_START _ADDR)"

The code is very simple and in prctice is only this declaration, the
others parts work correctly.

Thanks

[Anand]

mauri1106 wrote:

Hi, I have a little problem with a pointer.

In my project is included an ".h" file with this declaration:

"#define pMDMA_D0_START_ ADDR ((void * volatile *)MDMA_D0_START _ADDR)"

If I assign a value (e.g. *pMDMA_S0_START _ADDR = 0x04000;) the
compiler give me these 2 warning:

".\init.c", line 105: cc0513: {D} warning: a value of type "int" cannot
be assigned to an entity of type "void *"
*pMDMA_S0_START _ADDR = 0x04000;
^
".\init.c", line 105: cc0152: {D} warning: conversion of nonzero
integer to pointer
*pMDMA_S0_START _ADDR = 0x04000;
^
Why appears these warnings?

thanks, Maurizio

Searching the archives of the group would give the complete discussion
about this section.

Here's a snippet from standard:
"An integer may be converted to any pointer type. Except as previously
specified, the result is implementation-defined, might not be correctly
aligned, might not point to an entity of the referenced type, and might
be a trap representation. "

And hence the warnings from the compiler
--
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(clc FAQ) http://www.eskimo.com/~scs/C-faq/top.html

[mauri1106]

Dear anand, can you better explain your answer? I don't understand what
do you want to say.
thanks

[Anand]

<quote-correction>
mauri1106: Please ensure to quote the previous reply. This gives a
context to the mail. I've corrected this time.
</quote-correction>

Anand Wrote:

Here's a snippet from standard:
"An integer may be converted to any pointer type. Except as previously
specified, the result is implementation-defined, might not be correctly >aligned, might not point to an entity of the referenced type,
and might >be a trap representation. "
mauri1106 wrote:

Dear anand, can you better explain your answer? I don't understand what
do you want to say.
thanks

I assume you didn't search the archives of this group.

What you have is a void**ptr. So the moment you redirect it you have is
a void* (a pointer) and you are assigning an integer value to it.
And hence the warnings.

"ptr <- integer" is an implementation defined behavior and it's not
guaranteed to work.

Anyway, only valid and portable integer value that can be assigned to
any pointer is 0. (Which is NULL pointer).
If you are trying to assign any other integer to the pointer it purely
depends on your compiler and platform as to how to treat it.

The hard coded integer value you are assigning is purely dependent on
your environment in which the code is going to run.
For all you know you memory location 0x04000 could be invalid (you might
not have access to it).
Or there's no way to represent a memory location using just integers in
your system.

There are times when this may be valid (and in those cases you are very
much aware of it.) But then it's still the duty of your compiler to warn
you.

Now you decide, do you always have access to 0x4000 memory location (if
that's how you refer a location in your system) is valid and you have
full rights and doesn't cause any problem in that particular system.

--
(Welcome) http://www.ungerhu.com/jxh/clc.welcome.txt
(clc FAQ) http://www.eskimo.com/~scs/C-faq/top.html

[Anand]

Flash Gordon wrote:

mauri1106 wrote:

[...]

"#define pMDMA_D0_START_ ADDR ((void * volatile *)MDMA_D0_START _ADDR)" [...]

".\init.c", line 105: cc0513: {D} warning: a value of type "int" cannot
be
assigned to an entity of type "void *"
*pMDMA_S0_START _ADDR = 0x04000;

That's simple. void* is a generic pointer type, so of course you can't
read or write through a void* pointer. You need to have a pointer to a
complete, known type, e.g. int or char.

[...]
That's void** (or at least that's what it's type casted to). So in that
case doesn't it qualify to be a complete type? (of void*)

So for a "void *ptr" , doing "*ptr" is invalid.
But for "void **ptr", doing "*ptr" is fully valid.

Or did I miss something?
--
(Welcome) http://www.ungerhu.com/jxh/clc.welcome.txt
(clc FAQ) http://www.eskimo.com/~scs/C-faq/top.html

[Keith Thompson]

Anand <An***@no-replies.com> writes:

mauri1106 wrote:

Hi, I have a little problem with a pointer.
In my project is included an ".h" file with this declaration:
"#define pMDMA_D0_START_ ADDR ((void * volatile *)MDMA_D0_START _ADDR)"
If I assign a value (e.g. *pMDMA_S0_START _ADDR = 0x04000;) the
compiler give me these 2 warning:
".\init.c", line 105: cc0513: {D} warning: a value of type "int"
cannot
be assigned to an entity of type "void *"
*pMDMA_S0_START _ADDR = 0x04000;
^
".\init.c", line 105: cc0152: {D} warning: conversion of nonzero
integer to pointer
*pMDMA_S0_START _ADDR = 0x04000;
^
Why appears these warnings?
thanks, Maurizio

Searching the archives of the group would give the complete discussion
about this section.

Here's a snippet from standard:
"An integer may be converted to any pointer type. Except as previously
specified, the result is implementation-defined, might not be
correctly aligned, might not point to an entity of the referenced
type, and might be a trap representation. "

And hence the warnings from the compiler

In addition, the only *implicit* integer-to-pointer conversion is for
a null pointer constant. You can convert an integer value such as
0x04000 to a pointer type, but only with an explicit cast -- and of
course the result may or may not be meaningful.

void *p0 = 0; /* ok, 0 is a null pointer constant */
void *p1 = 42; /* illegal */
void *p2 = (void*)42; /* legal but questionable */

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.