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Improve format_as safety

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This commit is contained in:
Victor Zverovich 2023-03-19 06:51:47 -07:00
parent d9bc5f1320
commit 6549ffde8e
3 changed files with 24 additions and 41 deletions
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36
include/fmt/core.h
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@ -291,7 +291,8 @@
// Enable minimal optimizations for more compact code in debug mode.
FMT_GCC_PRAGMA("GCC push_options")
#if !defined(__OPTIMIZE__) && !defined(__NVCOMPILER) && !defined(__LCC__) && !defined(__CUDACC__)
#if !defined(__OPTIMIZE__) && !defined(__NVCOMPILER) && !defined(__LCC__) && \
!defined(__CUDACC__)
FMT_GCC_PRAGMA("GCC optimize(\"Og\")")
#endif
@ -1364,20 +1365,19 @@ inline auto format_as(std::byte b) -> unsigned char {
}
#endif
template <typename T> struct convertible_to { operator const T&() const; };
template <typename T> struct format_as_result {
template <typename U,
FMT_ENABLE_IF(std::is_enum<U>::value || std::is_class<U>::value)>
static auto map(U*) -> decltype(format_as(std::declval<U>()));
static auto map(...) -> void;
template <typename T> struct has_format_as {
template <typename U, typename V = decltype(format_as(U())),
FMT_ENABLE_IF(std::is_enum<U>::value)>
static auto check(U*) -> std::true_type;
// Use convertible_to to avoid implicit conversions.
template <typename U, typename V = decltype(format_as(convertible_to<U>())),
FMT_ENABLE_IF(std::is_class<U>::value)>
static auto check(U*) -> std::true_type;
static auto check(...) -> std::false_type;
enum { value = decltype(check(static_cast<T*>(nullptr)))::value };
using type = decltype(map(static_cast<T*>(nullptr)));
};
template <typename T> using format_as_t = typename format_as_result<T>::type;
template <typename T>
struct has_format_as
: bool_constant<!std::is_same<format_as_t<T>, void>::value> {};
// Maps formatting arguments to core types.
// arg_mapper reports errors by returning unformattable instead of using
@ -1495,10 +1495,10 @@ template <typename Context> struct arg_mapper {
}
#endif
template <typename T, FMT_ENABLE_IF(has_format_as<T>::value &&
!has_formatter<T, Context>::value)>
FMT_CONSTEXPR FMT_INLINE auto map(const T& val)
-> decltype(this->map(format_as(T()))) {
// Only map owning types because mapping views can be unsafe.
template <typename T, typename U = format_as_t<T>,
FMT_ENABLE_IF(std::is_arithmetic<U>::value)>
FMT_CONSTEXPR FMT_INLINE auto map(const T& val) -> decltype(this->map(U())) {
return map(format_as(val));
}
@ -1529,7 +1529,7 @@ template <typename Context> struct arg_mapper {
FMT_ENABLE_IF(!is_string<U>::value && !is_char<U>::value &&
!std::is_array<U>::value &&
!std::is_pointer<U>::value &&
!has_format_as<U>::value &&
!std::is_arithmetic<format_as_t<U>>::value &&
(has_formatter<U, Context>::value ||
has_fallback_formatter<U, char_type>::value))>
FMT_CONSTEXPR FMT_INLINE auto map(T&& val)

8
test/core-test.cc
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@ -677,8 +677,11 @@ namespace test {
enum class scoped_enum_as_int {};
auto format_as(scoped_enum_as_int) -> int { return 42; }
enum class scoped_enum_as_string_view {};
auto format_as(scoped_enum_as_string_view) -> fmt::string_view { return "foo"; }
enum class scoped_enum_as_string {};
auto format_as(scoped_enum_as_string) -> fmt::string_view { return "foo"; }
auto format_as(scoped_enum_as_string) -> std::string { return "foo"; }
struct struct_as_int {};
auto format_as(struct_as_int) -> int { return 42; }
@ -740,7 +743,8 @@ TEST(core_test, format_to) {
TEST(core_test, format_as) {
EXPECT_EQ(fmt::format("{}", test::scoped_enum_as_int()), "42");
EXPECT_EQ(fmt::format("{}", test::scoped_enum_as_string()), "foo");
// EXPECT_EQ(fmt::format("{}", test::scoped_enum_as_string_view()), "foo");
// EXPECT_EQ(fmt::format("{}", test::scoped_enum_as_string()), "foo");
EXPECT_EQ(fmt::format("{}", test::struct_as_int()), "42");
}

21
test/format-test.cc
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@ -1641,27 +1641,6 @@ TEST(format_test, format_explicitly_convertible_to_std_string_view) {
}
#endif
struct converible_to_anything {
template <typename T> operator T() const { return T(); }
};
FMT_BEGIN_NAMESPACE
template <> struct formatter<converible_to_anything> {
FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
return ctx.begin();
}
auto format(converible_to_anything, format_context& ctx)
-> decltype(ctx.out()) {
return format_to(ctx.out(), "foo");
}
};
FMT_END_NAMESPACE
TEST(format_test, format_convertible_to_anything) {
EXPECT_EQ("foo", fmt::format("{}", converible_to_anything()));
}
class Answer {};
FMT_BEGIN_NAMESPACE