https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115125
Bug ID: 115125
Summary: [-Wstringop-overflow=] with O2/O3 - false positive?
Product: gcc
Version: 14.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: oknenavin at outlook dot com
Target Milestone: ---
$ g++ --version
g++.exe (Rev2, Built by MSYS2 project) 14.1.0
test.cxx:
template <typename II>
inline char peek(II i, II e) { return i != e ? *i : '\xFF'; }
template <typename II>
inline char next(II& i, II e) { return peek(++i, e); }
#define READ() *f = c, c = next(i, e), ++f;
#define NEXT() { if (f == l) return -1; READ() }
template <typename II>
inline int consume(char* f, const char* l, II& i, II e)
{
char c = peek(i, e);
if (c == '"') {
; READ()
if (c == '-') NEXT()
if (c == 'i') {
NEXT() if (c != 'n') return 0;
NEXT() if (c != 'f') return 0;
}
else if (c == 'n') {
NEXT() if (c != 'a') return 0;
NEXT() if (c != 'n') return 0;
}
else return 0;
NEXT() if (c != '"') return 0;
NEXT()
}
return f != l ? (*f = '\0', 1) : -1;
}
int main(int argc, char* argv[]) {
char bf[3];
consume(bf, bf + 3, argv[0], argv[0] + 16);
//char* in = argv[0];
//consume(bf, bf + 3, in, in + 16);
}
$ g++ -c -O2 test.cxx
In function 'int consume(char*, const char*, II&, II) [with II = char*]',
inlined from 'int main(int, char**)' at test.cxx:33:12:
test.cxx:6:19: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
6 | #define READ() *f = c, c = next(i, e), ++f;
| ~~~^~~
test.cxx:7:41: note: in expansion of macro 'READ'
7 | #define NEXT() { if (f == l) return -1; READ() }
| ^~~~
test.cxx:25:17: note: in expansion of macro 'NEXT'
25 | NEXT() if (c != '"') return 0;
| ^~~~
test.cxx: In function 'int main(int, char**)':
test.cxx:32:10: note: at offset [1, 3] into destination object 'bf' of size
3
32 | char bf[3];
| ^~
test.cxx:32:10: note: at offset [2, 3] into destination object 'bf' of size
3
test.cxx:32:10: note: at offset [1, 3] into destination object 'bf' of size
3
test.cxx:32:10: note: at offset [2, 3] into destination object 'bf' of size
3
