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Check dynamic width/precision id at compile time (#1614)

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This commit is contained in:
Victor Zverovich 2020-04-22 14:18:45 -07:00
parent e51c449fe6
commit 1e1ac6e964
3 changed files with 36 additions and 12 deletions
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2
include/fmt/core.h
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@ -568,7 +568,7 @@ class basic_format_parse_context : private ErrorHandler {
using iterator = typename basic_string_view<Char>::iterator;
explicit FMT_CONSTEXPR basic_format_parse_context(
basic_string_view<Char> format_str, ErrorHandler eh = ErrorHandler())
basic_string_view<Char> format_str, ErrorHandler eh = {})
: ErrorHandler(eh), format_str_(format_str), next_arg_id_(0) {}
/**

44
include/fmt/format.h
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@ -2626,25 +2626,51 @@ FMT_CONSTEXPR const typename ParseContext::char_type* parse_format_specs(
return f.parse(ctx);
}
// A parse context with extra argument id checks. It is only used at compile
// time because adding checks at runtime would introduce substantial overhead
// and would be redundant since argument ids are checked when arguments are
// retrieved anyway.
template <typename Char, typename ErrorHandler = error_handler>
class compile_parse_context
: public basic_format_parse_context<Char, ErrorHandler> {
private:
int num_args_;
using base = basic_format_parse_context<Char, ErrorHandler>;
public:
explicit FMT_CONSTEXPR compile_parse_context(
basic_string_view<Char> format_str, int num_args = max_value<int>(),
ErrorHandler eh = {})
: base(format_str, eh), num_args_(num_args) {}
FMT_CONSTEXPR int next_arg_id() {
int id = base::next_arg_id();
if (id >= num_args_) this->on_error("argument not found");
return id;
}
FMT_CONSTEXPR void check_arg_id(int id) {
base::check_arg_id(id);
if (id >= num_args_) this->on_error("argument not found");
}
using base::check_arg_id;
};
template <typename Char, typename ErrorHandler, typename... Args>
class format_string_checker {
public:
explicit FMT_CONSTEXPR format_string_checker(
basic_string_view<Char> format_str, ErrorHandler eh)
: arg_id_(-1),
context_(format_str, eh),
context_(format_str, num_args, eh),
parse_funcs_{&parse_format_specs<Args, parse_context_type>...} {}
FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
FMT_CONSTEXPR void on_arg_id() {
arg_id_ = context_.next_arg_id();
check_arg_id();
}
FMT_CONSTEXPR void on_arg_id() { arg_id_ = context_.next_arg_id(); }
FMT_CONSTEXPR void on_arg_id(int id) {
arg_id_ = id;
context_.check_arg_id(id);
check_arg_id();
}
FMT_CONSTEXPR void on_arg_id(basic_string_view<Char>) {
on_error("compile-time checks don't support named arguments");
@ -2662,13 +2688,9 @@ class format_string_checker {
}
private:
using parse_context_type = basic_format_parse_context<Char, ErrorHandler>;
using parse_context_type = compile_parse_context<Char, ErrorHandler>;
enum { num_args = sizeof...(Args) };
FMT_CONSTEXPR void check_arg_id() {
if (arg_id_ >= num_args) context_.on_error("argument not found");
}
// Format specifier parsing function.
using parse_func = const Char* (*)(parse_context_type&);

2
test/format-test.cc
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@ -2493,6 +2493,8 @@ TEST(FormatTest, FormatStringErrors) {
EXPECT_ERROR("{:+}", "format specifier requires signed argument", unsigned);
EXPECT_ERROR("{:-}", "format specifier requires signed argument", unsigned);
EXPECT_ERROR("{: }", "format specifier requires signed argument", unsigned);
EXPECT_ERROR("{:{}}", "argument not found", int);
EXPECT_ERROR("{:.{}}", "argument not found", double);
EXPECT_ERROR("{:.2}", "precision not allowed for this argument type", int);
EXPECT_ERROR("{:s}", "invalid type specifier", int);
EXPECT_ERROR("{:s}", "invalid type specifier", bool);