https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104828
Bug ID: 104828
Summary: Wrong out-of-bounds array access warning on literal
pointers
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: goswin-v-b at web dot de
Target Milestone: ---
Trying to access a pointer cast from an integer literal gives a out of bounds
warning:
--------------------------------------------------------------------------
#define UART0_BASE 0x3F201000
void putc(char c) {
volatile unsigned int *UART0_DR = (volatile unsigned int *)(UART0_BASE);
volatile unsigned int *UART0_FR = (volatile unsigned int *)(UART0_BASE +
0x18);
while (*UART0_FR & (1 << 5) ) { }
*UART0_DR = c;
}
--------------------------------------------------------------------------
<source>:5:3: warning: array subscript 0 is outside array bounds of 'volatile
unsigned int [0]' [-Warray-bounds]
5 | *UART0_DR = c;
| ^~~~~~~~~
The error goes away if the pointer is global or static.
The error remains if the pointer is returned from a function with alloc_size
attribute:
--------------------------------------------------------------------------
#include <unistd.h>
#include <cstdint>
#define UART0_BASE 0x3F201000
volatile uint32_t * make(uintptr_t addr, size_t size = 4) __attribute__
((alloc_size (2)));
volatile uint32_t * make(uintptr_t addr, size_t size) {
(void)size;
return (volatile uint32_t *)addr;
}
void putc(char c) {
volatile uint32_t *UART0_DR = make(UART0_BASE);
volatile uint32_t *UART0_FR = make(UART0_BASE + 0x18);
while (*UART0_FR & (1 << 5) ) { }
*UART0_DR = c;
}
--------------------------------------------------------------------------
<source>:16:3: warning: array subscript 0 is outside array bounds of 'volatile
uint32_t [0]' [-Warray-bounds]
16 | *UART0_DR = c;
| ^~~~~~~~~
The warning goes away if the "make" helper is extern and can't be inlined.
Gcc 11.2 and before do not give this warning.
