https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578
Bug ID: 99578
Summary: gcc-11 -Warray-bounds or -Wstringop-overread warning
when accessing a pointer from integer literal
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: arnd at linaro dot org
Target Milestone: ---
This snippet from the Linux kernel reads a data structure from an
architecturally defined location in memory into a local copy:
struct sharpsl_param_info {
unsigned int comadj_keyword;
};
extern struct sharpsl_param_info sharpsl_param;
typedef unsigned long __kernel_size_t;
extern void * memcpy(void *, const void *, __kernel_size_t);
void sharpsl_save_param(void)
{
memcpy(&sharpsl_param, (void *)(0xe8ffc000), sizeof(struct
sharpsl_param_info));
}
With gcc-11, this now triggers a -Wstringop-overread warning on x86:
arch/arm/common/sharpsl_param.i: In function ‘sharpsl_save_param’:
arch/arm/common/sharpsl_param.i:11:2: warning: ‘memcpy’ reading 4 bytes from a
region of size 0 [-Wstringop-overread]
11 | memcpy(&sharpsl_param, (void *)(0xe8ffc000), sizeof(struct
sharpsl_param_info));
I tried to reproduce this on godbolt.org, which apparently has a slightly
different snapshot version and instead produces -Warray-bounds warning for the
same input: https://godbolt.org/z/ve6h6b
I could not find a way to avoid this warning, other than turning off the entire
warning option globally or with a pragma. Accessing a pointer from a literal
integer value is not too unusual in the kernel and should not cause a warning.
