| Issue |
126389
|
| Summary |
`-Wformat-security` false-positive in consteval functions
|
| Labels |
false-positive
|
| Assignees |
|
| Reporter |
vvd170501
|
Reproducer:
```cpp
void FormatFunc(const char* format, ...) __attribute__((__format__(__printf__, 1, 2)));
consteval void Foo() {
if (false) {
FormatFunc("test"); // error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
}
}
constexpr void Bar() {
if (false) {
FormatFunc("test"); // ok in constexpr
}
}
consteval void Baz() {
if (false) {
FormatFunc("%s", "test"); // Adding a second arg somehow fixes the warning
}
}
```
The warning is present in clang trunk (https://godbolt.org/z/PxqzfE1W7) and in all recent versions of clang (I checked clang16-clang19).
<details><summary>A more realistic example:</summary>
```cpp
[[noreturn]] void Panic(const char* format, ...) noexcept __attribute__((__format__(__printf__, 1, 2)));
// assert()-like macro which allows adding description to failure message
#define FANCY_ASSERT(x, ...) \
if (!(x)) { \
Panic(" " __VA_ARGS__); \
}
constexpr int NonZeroConstexpr(int x) {
FANCY_ASSERT(x);
return x;
}
constexpr int x1 = NonZeroConstexpr(1); // ok
// constexpr int x2 = NonZeroConstexpr(0); // error - Panic(...) is not constexpr
// Same, but with consteval
consteval int NonZeroConsteval(int x) {
FANCY_ASSERT(x); // error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
return x;
}
```
</details>
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