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Report error on duplicate named arg names #4367

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Report error on duplicate named arg names #4367

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167ec54
Report error on duplicate named arg names
dinomight Feb 22, 2025
233d8d9
Fix unused return warning
dinomight Feb 26, 2025
3d9a3e6
Fix formatting
dinomight Feb 26, 2025
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12 changes: 12 additions & 0 deletions include/fmt/base.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1071,6 +1071,12 @@ void init_named_arg(named_arg_info<Char>*, int& arg_index, int&, const T&) {
template <typename Char, typename T, FMT_ENABLE_IF(is_named_arg<T>::value)>
void init_named_arg(named_arg_info<Char>* named_args, int& arg_index,
int& named_arg_index, const T& arg) {
for (auto i = 0; i < named_arg_index; ++i) {
if (basic_string_view<Char>(named_args[i].name) ==
basic_string_view<Char>(arg.name)) {
report_error("duplicate named args found");
}
}
named_args[named_arg_index++] = {arg.name, arg_index++};
}

Expand All @@ -1084,6 +1090,12 @@ template <typename T, typename Char,
FMT_ENABLE_IF(is_static_named_arg<T>::value)>
FMT_CONSTEXPR void init_static_named_arg(named_arg_info<Char>* named_args,
int& arg_index, int& named_arg_index) {
for (auto i = 0; i < named_arg_index; ++i) {
if (basic_string_view<Char>(named_args[i].name) ==
basic_string_view<Char>(T::name)) {
report_error("duplicate named args found");
}
}
named_args[named_arg_index++] = {T::name, arg_index++};
}

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8 changes: 8 additions & 0 deletions test/compile-error-test/CMakeLists.txt
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Expand Up @@ -209,6 +209,14 @@ if (CMAKE_CXX_STANDARD GREATER_EQUAL 20)
#error
#endif
" ERROR)
expect_compile(format-string-duplicate-name-error "
#if defined(FMT_HAS_CONSTEVAL) && FMT_USE_NONTYPE_TEMPLATE_ARGS
using namespace fmt::literals;
fmt::print(\"{bar}\", \"bar\"_a=42, \"bar\"_a=43);
#else
#error
#endif
" ERROR)
endif ()

# Run all tests
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2 changes: 2 additions & 0 deletions test/format-test.cc
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Expand Up @@ -599,6 +599,8 @@ TEST(format_test, named_arg) {
EXPECT_THROW_MSG((void)fmt::format(runtime("{a} {}"), fmt::arg("a", 2), 42),
format_error,
"cannot switch from manual to automatic argument indexing");
EXPECT_THROW_MSG((void)fmt::format("{enum}", fmt::arg("enum", 1),
fmt::arg("enum", 10)), format_error, "duplicate named args found");
}

TEST(format_test, auto_arg_index) {
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