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Currently, if unwrap fails, it simply triggers an assertion failure, which provides no indication as to what happened.

xinit uses %h during startup in some print statement. I haven't been able to identify which, what or when. The following is logged in E9.

mlibc: Unknown printf terminator '104'

While this behavior is probably fine, it would be desirable to be able to chain expecteds for monadic operations.

For an example of such see Haskell's Either

-- Module      :  Data.Either
-- Copyright   :  (c) The University of Glasgow 2001
-- License     :  BSD-style (see the file libraries/base/LICENSE)

-- | @since 4.4.0.0
instance Monad (Either e) where
    Left  l >>= _ = Left l
    Right r >>= k = k r

In essence, this means that >>= propagates error and does not evaluate k (type: a -> Either e b) unless the Either is a Right (success case)

EDIT: similarly, there's no way to implicitly convert to a different expected result of same error (one would have to do if (!e) { {co_}return e.error(); })

(In formatting.hpp, do_printf_chars)
case 'c': FRG_ASSERT(!opts.fill_zeros); FRG_ASSERT(!opts.left_justify); FRG_ASSERT(!opts.alt_conversion); ---->FRG_ASSERT(szmod == printf_size_mod::default_size); Fails when running Python 3.8

While running nyancat on Managarm, the following assertion failure message is printed continuously:

../../../src/mlibc/subprojects/frigg/include/frg/formatting.hpp:231: Assertion 'padding == ' '' failed!

Relevant code snippet for context:

template<typename P, typename T>
	void print_float(P &formatter, T number, int width = 0, int precision = 6,
			char padding = ' ', bool left_justify = false, bool use_capitals = false,
			bool group_thousands = false, locale_options locale_opts = {}) {
		(void)group_thousands;
		FRG_DEBUG_ASSERT(padding == ' '); // <-- This assert fails

		bool has_sign = false;
		if (number < 0) {
			formatter.append('-');
			has_sign = true;
		}

		bool inf = __builtin_isinf(number), nan = __builtin_isnan(number);
		if (inf || nan) {
			auto total_length = 3 + has_sign;
			auto pad_length = width > total_length ? width - total_length : 0;
			if (!left_justify) {
				while (pad_length > 0) {
					formatter.append(padding);
					pad_length--;
				}
			}

			if (inf)
				formatter.append(use_capitals ? "INF" : "inf");
			else
				formatter.append(use_capitals ? "NAN" : "nan");

			if (left_justify) {
				while (pad_length > 0) {
					formatter.append(padding);
					pad_length--;
				}
			}

			return;
		}

The old frigg had a nice priority queue based on binary heaps (source code). Import it into this repository.

The following program fails to compile:

#include <frg/array.hpp>

class ConstArrayTest 
{
public:
    const int *data() const
    {
        return arr_.data();
    }

private:
    frg::array<int, 5> arr_;
};

ConstArrayTest<int> t;

include/frg/array.hpp:74:30: error: invalid conversion from ‘const value_type*’ {aka ‘const int*’} to ‘int*’ [-fpermissive]
   74 |                 return &_stor[0];
      |                         ~~~~~^
      |                              |
      |                              const value_type* {aka const int*}

This seems to be because in array.hpp the return type of array::data() const is marked constexpr but not const (constexpr makes the pointer type const, but not the pointed-to value).

 constexpr T* data() const noexcept {
//         ^
//         |
//         should be constexpr const T*!
    return &_stor[0];
}

I'm not sure why it works when templated, though.

// compiles no problem

template <typename T>
class ConstArrayTest 
{
public:
    const T *data() const
    {
        return arr_.data();
    }

private:
    frg::array<T, 5> arr_;
};

ConstArrayTest<int> t;

Both examples compile with the GNU implementation of the C++ Standard Library, which does declare the return type const:

_GLIBCXX17_CONSTEXPR const_pointer
data() const noexcept
{ return _AT_Type::_S_ptr(_M_elems); }

Currently, this makes downstream CI fail: https://github.com/managarm/managarm/runs/6953595720

%g, %G, %e, %E are unimplemented, which breaks Xash3D.

While testing out the fixes for #14, I ran into the following problem

../../../src/mlibc/subprojects/frigg/include/frg/printf.hpp:57: Assertion 'opts->arg_pos <= vsp->num_args' failed!

Tested with the --help commands of:

• mount,
• fdisk,
• choom,
• findmnt,
• flock,
• getopt,
• mountpoint,
• renice,
• umount,
• agetty,
• cfdisk,
• losetup,
• sfdisk,
• zramctl.

Certain basic_string operations (such as comparisons) can be implemented in terms of basic_string_view: e.g.:

bool operator==(const basic_string &other) const {
    return basic_string_view<Char>{_buffer, _length} == basic_string_view<Char>{other._buffer, other._length};
}

We could also add a convenience basic_string::view() method that does the view construction.

Doing this will allow us to more easily prevent bugs like the one fixed by 264af2d.

The following applications from util-linux use $ while printing their help message.

• mount,
• fdisk,
• choom,
• findmnt,
• flock,
• getopt,
• mountpoint,
• renice,
• umount,
• agetty,
• cfdisk,
• losetup,
• sfdisk,
• zramctl.

The following is logged in E9 for all of them.

mlibc: Unknown printf terminator '36'