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From: "visenri at yahoo dot es" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/59773] New: Mixing pointers to different memory spaces shows no warning (gcc for AVR)
Date: Sun, 12 Jan 2014 00:28:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59773

            Bug ID: 59773
           Summary: Mixing pointers to different memory spaces shows no
                    warning (gcc for AVR)
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: visenri at yahoo dot es

I'll explain it with an example.

Having these strings declared:

const char __flash strF[] = "Flash";
const char         strR[] = "RAM";

And a function with a 24 bit flat pointer like this:

Foo( const char __memx * str );

Calling it like this is ok (16 bit pointer is enlarged to 24 generating correct
code):

Foo(strF);
Foo(strR);

But using functions with 16 bit pointer:

FooR( const char * str ); //16 bit pointer to RAM
FooF( const char _flash * str ); //16 bit pointer to FLASH

And these variables:

const char __memx * pstr;
const char * pstrR;
const char __flash * pstrF;

These lines should show at least a warning:

FooR(strF); // same size, different memory space
FooF(strR); // same size, different memory space
FooR(pstr); // pstr is 24 bit, bigger than 16 bit ram pointer in function
FooF(pstr); // pstr is 24 bit, bigger than 16 bit flash pointer in function

pstrR = strF; // same size, different memory space
pstrF = strR; // same size, different memory space
pstrR = pstr; // pstr is 24 bit, bigger than 16 bit ram pointer
pstrF = pstr; // pstr is 24 bit, bigger than 16 bit flash pointer

Because we are going to use a ROM/FLASH pointer as a RAM pointer or the other
way.