04e6178ae9
It's been reported that when using __attribute__((format)) on non-variadic
functions, certain values that normally get promoted when passed as variadic
arguments now unconditionally emit a diagnostic:
```c
void foo(const char *fmt, float f) __attribute__((format(printf, 1, 2)));
void bar(void) {
foo("%g", 123.f);
// ^ format specifies type 'double' but the argument has type 'float'
}
```
This is normally not an issue because float values get promoted to doubles when
passed as variadic arguments, but needless to say, variadic argument promotion
does not apply to non-variadic arguments.
While this can be fixed by adjusting the prototype of `foo`, this is sometimes
undesirable in C (for instance, if `foo` is ABI). In C++, using variadic
templates, this might instead require call-site fixing, which is tedious and
arguably needless work:
```c++
template<typename... Args>
void foo(const char *fmt, Args &&...args) __attribute__((format(printf, 1, 2)));
void bar(void) {
foo("%g", 123.f);
// ^ format specifies type 'double' but the argument has type 'float'
}
```
To address this issue, we teach FormatString about a few promotions that have
always been around but that have never been exercised in the direction that
FormatString checks for:
* `char`, `unsigned char` -> `int`, `unsigned`
* `half`, `float16`, `float` -> `double`
This addresses issue https://github.com/llvm/llvm-project/issues/59824.
97 lines
3.7 KiB
C++
97 lines
3.7 KiB
C++
// RUN: %clang_cc1 -fsyntax-only -Wformat-nonliteral -verify %s
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#include <stdarg.h>
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int printf(const char *fmt, ...) __attribute__((format(printf, 1, 2)));
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struct S {
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static void f(const char *, ...) __attribute__((format(printf, 1, 2)));
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static const char *f2(const char *) __attribute__((format_arg(1)));
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// GCC has a hidden 'this' argument in member functions which is why
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// the format argument is argument 2 here.
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void g(const char*, ...) __attribute__((format(printf, 2, 3)));
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const char* g2(const char*) __attribute__((format_arg(2)));
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void h(const char*, ...) __attribute__((format(printf, 1, 4))); // \
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expected-error{{implicit this argument as the format string}}
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void h2(const char*, ...) __attribute__((format(printf, 2, 1))); // \
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expected-error{{out of bounds}}
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const char* h3(const char*) __attribute__((format_arg(1))); // \
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expected-error{{invalid for the implicit this argument}}
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void operator() (const char*, ...) __attribute__((format(printf, 2, 3)));
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};
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// PR5521
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struct A { void a(const char*,...) __attribute((format(printf,2,3))); };
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void b(A x) {
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x.a("%d", 3);
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}
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// PR8625: correctly interpret static member calls as not having an implicit
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// 'this' argument.
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namespace PR8625 {
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struct S {
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static void f(const char*, const char*, ...)
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__attribute__((format(printf, 2, 3)));
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};
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void test(S s, const char* str) {
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s.f(str, "%s", str);
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}
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}
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// Make sure we interpret member operator calls as having an implicit
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// this argument.
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void test_operator_call(S s, const char *str) {
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s("%s", str);
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}
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template <typename... Args>
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void format(const char *fmt, Args &&...args) // expected-warning{{GCC requires a function with the 'format' attribute to be variadic}}
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__attribute__((format(printf, 1, 2)));
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template <typename Arg>
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Arg &expand(Arg &a) { return a; }
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struct foo {
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int big[10];
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foo();
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~foo();
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template <typename... Args>
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void format(const char *const fmt, Args &&...args) // expected-warning{{GCC requires a function with the 'format' attribute to be variadic}}
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__attribute__((format(printf, 2, 3))) {
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printf(fmt, expand(args)...);
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}
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};
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void format_invalid_nonpod(const char *fmt, struct foo f) // expected-warning{{GCC requires a function with the 'format' attribute to be variadic}}
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__attribute__((format(printf, 1, 2)));
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void do_format() {
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int x = 123;
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int &y = x;
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const char *s = "world";
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bool b = false;
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format("bare string");
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format("%s", 123); // expected-warning{{format specifies type 'char *' but the argument has type 'int'}}
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format("%s %s %u %d %i %p\n", "hello", s, 10u, x, y, &do_format);
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format("%s %s %u %d %i %p\n", "hello", s, 10u, x, y, do_format);
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format("bad format %s"); // expected-warning{{more '%' conversions than data arguments}}
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format("%c %c %hhd %hd %d\n", (char)'a', 'a', 'a', (short)123, (int)123);
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format("%f %f %f\n", (__fp16)123.f, 123.f, 123.);
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format("%Lf", (__fp16)123.f); // expected-warning{{format specifies type 'long double' but the argument has type '__fp16'}}
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format("%Lf", 123.f); // expected-warning{{format specifies type 'long double' but the argument has type 'float'}}
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format("%hhi %hhu %hi %hu %i %u", b, b, b, b, b, b);
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format("%li", b); // expected-warning{{format specifies type 'long' but the argument has type 'bool'}}
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struct foo f;
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format_invalid_nonpod("hello %i", f); // expected-warning{{format specifies type 'int' but the argument has type 'struct foo'}}
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f.format("%s", 123); // expected-warning{{format specifies type 'char *' but the argument has type 'int'}}
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f.format("%s %s %u %d %i %p\n", "hello", s, 10u, x, y, &do_format);
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f.format("%s %s %u %d %i %p\n", "hello", s, 10u, x, y, do_format);
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f.format("bad format %s"); // expected-warning{{more '%' conversions than data arguments}}
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}
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