https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84166
Bug ID: 84166
Summary: Wrong warning message emitted for loss of qualifiers
Product: gcc
Version: 6.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: ttsiodras at gmail dot com
Target Milestone: ---
The code shown below...
#include <stdlib.h>
#include <stdint.h>
extern void get_buffer_from_HW_driver(volatile uint32_t **p);
void getBuffer(volatile uint32_t **pp)
{
// Write an address into p, that is obtained from a driver
// The underlying HW will be DMA-ing into this address,
// so the data pointed-to by the pointer returned by this
// call are volatile.
get_buffer_from_HW_driver(pp);
}
void work()
{
uint32_t *p = NULL;
getBuffer((volatile uint32_t **)&p);
}
...is erroneously forgetting to set the `volatile` qualifier for the pointer
`p` declared in `work`. Unfortunately, GCC's related warning indicates that
there is a missing `const` - instead of a missing `volatile`:
$ gcc -c -Wall -Wextra -Wcast-qual constqual.c
constqual.c: In function ‘work’:
constqual.c:20:15: warning: to be safe all intermediate pointers in cast
from
‘uint32_t ** {aka unsigned int **}’ to ‘volatile uint32_t **
{aka volatile unsigned int **}’ must be ‘const’ qualified
[-Wcast-qual]
getBuffer((volatile uint32_t **)&p);
^
It appears that GCC confuses `const` with `volatile` here.
