https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83373
Bug ID: 83373
Summary: False positive reported by -Wstringop-overflow
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
When code below is compiled, gcc incorrectly complains that memcpy will read
data after end of buffer in line marked with star. Looks that gcc does not take
into account that 'if' above protects against this.
Code was compiles using gcc (GCC) 8.0.0 20171210 (experimental).
[code]
#include <string.h>
char buf[100];
void get_data(char* ptr);
__attribute((nonnull(1, 2)))
inline char* my_strcpy(char* __restrict__ dst, const char* __restrict__ src,
size_t size)
{
size_t len = strlen(src);
if (len < size)
memcpy(dst, src, len + 1);
else
{
memcpy(dst, src, size - 1); //*
dst[size - 1] = '\0';
}
return dst;
}
void test()
{
char data[20];
get_data(data);
my_strcpy(buf, data, sizeof(buf));
}
[/code]
[out]
$ g++ -c -o test.o test.cc -O2 -Wall
In function ‘char* my_strcpy(char*, const char*, size_t)’,
inlined from ‘void test()’ at test.cc:25:14:
test.cc:15:15: warning: ‘void* memcpy(void*, const void*, size_t)’ reading 99
bytes from a region of size 20 [-Wstringop-overflow=]
memcpy(dst, src, size - 1); //*
~~~~~~^~~~~~~~~~~~~~~~~~~~
[/out]
