Git issue 040 (#41)

* Correct C++11 <cmath> and docs

* Update CI

* Repair CI and more update docs

* Try to repair CI

* Try again to repair CI

* Update docs again

* cmath: Restore definitions of std::fpclassify

This partially reverts 5a4c53d and adds
the constants needed for it to work.

Fixes: #40

* Repait lex-parser issue on GCC 15.1.0

* Manual merge jwakely <cmath> corrections

* Update docs yet again

---------

Co-authored-by: Jonathan Wakely <[email protected]>

Author: ckormanyos

.github/workflows/compile_examples.yml

@@ -8,7 +8,7 @@ on:
 
 jobs:
   unittests-linux-generic:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     container:
       image: ghcr.io/modm-ext/modm-build-avr:latest
 
@@ -19,7 +19,7 @@ jobs:
 
     steps:
       - name: Check out repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Check environment
         run: |

README.md

@@ -238,12 +238,9 @@ and their directly relevant code sequences have been removed.
 Simple mechanisms such as those found in `<cassert>`
 and `<cerrno>`, however, remain mostly available.
 
-- **`<atomic>`:** Even though the intended compilers are built with no threading,
-the `<atomic>` library and its use as a dependency has
-been removed. This means that atomic functions and
-atomic store/load functions are not available. So if you are sharing
-data in an operating system or mixed program/interrupt mode,
-self-written atomic primitives are needed.
+- **`<atomic>`:** The `<atomic>` library is being handled
+specifically in the draft of
+[avr-libstdcpp/pull/36](https://github.com/modm-io/avr-libstdcpp/pull/36).
 
 - **`<random>`:** There is no source of entropy whatsoever on these platforms
 in their standard configuration. So `std::random_device`
@@ -280,12 +277,6 @@ The widths depend on the compiler command line options `-mdouble=32`
 `std::exp()` and the like will, therefore, have input and output
 widths according to these command line options.
 
-- **`<cmath>`:** In compiler versions of `avr-gcc` 11 and higher,
-slight discrepancies in the signatures of functions like
-`isnan()`, `isinf()`, etc. seem to be in the process of being corrected.
-Future patches of math function signatures in `<cmath>`
-may be needed as the `<math.h>` header continues to evolve.
-
 ## C++20 `constexpr` support
 
 The following is a rather advanced, highly useful topic.
@@ -337,18 +328,24 @@ int main()
 ```
 
 See also the [numeric.cpp](./examples/numeric/numeric.cpp) file
-in the [./examples/numeric](./examples/numeric) directory.
+in the [/examples/numeric](./examples/numeric) directory.
 
 ## Additional details
 
 `avr-libstdcpp` is intended for a modern `avr-gcc`
-such as the 11.2 port available in the [modm-io project](https://github.com/modm-io/avr-gcc)
-repository. Tests show usability also for `avr-gcc` 10 through 13 (and beyond).
+such as the port available in the [modm-io project](https://github.com/modm-io/avr-gcc)
+repository. Tests show usability for `avr-gcc` 7 through 15.
+
+This library has been checked for compatibility on `avr-gcc`
+with language standards C++11,14,17,20,23 and 2c.
 
-Using the port way back to `avr-gcc` 5, however, does not work
+Using the port way back to `avr-gcc` 5 does not work
 at the moment with today's form of the checked-in library,
-as the older compiler's lexical parser is not capable of
-properly handling some of the library's template code.
+and `avr-gcc` 7 or higher is required.
+This is because the very old compiler lexical parsers are not capable
+of properly handling some of the library's template code.
+See also [avr-libstdcpp/issues/15](https://github.com/modm-io/avr-libstdcpp/issues/15)
+which is closed and includes justification for its closure.
 
 ## Licensing
 
@@ -357,6 +354,6 @@ and the library include files in [`include/` and its subfolders](./include/)
 (with two exceptions for the sources, as mentioned below)
 are licensed under [GNU General Public License Version 3](./COPYING3) or higher.
 
-The [example codes](./examples/) and two library source files
+All of the [example codes](./examples/) and also two library source files
 (namely `functexcept.cc` and `math.cc` in [`src/`](./src/))
 are subject to the terms of the [Mozilla Public License Version 2.0](./COPYING.MPLv2).

examples/cmath/cmath.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Christopher Kormanyos
+ * Copyright (c) 2022, 2025, Christopher Kormanyos
  *
  * This file is part of the modm project.
  *
@@ -33,7 +33,7 @@ auto integral
 	real_value_type step = ((b - a) / 2U);
 	real_value_type result = (real_function(a) + real_function(b)) * step;
 
-	const std::uint_fast8_t k_max = UINT8_C(32);
+	constexpr std::uint_fast8_t k_max { UINT8_C(32) };
 
 	for(std::uint_fast8_t k = UINT8_C(0); k < k_max; ++k)
 	{
@@ -80,12 +80,29 @@ auto is_close_fraction
 	using floating_point_type = FloatingPointType;
 
 	using std::fabs;
+	using std::fpclassify;
 
-	const floating_point_type ratio     = fabs(floating_point_type((floating_point_type(1) * a) / b));
+	const int fpc_a { fpclassify(a) };
+	const int fpc_b { fpclassify(b) };
 
-	const floating_point_type closeness = fabs(floating_point_type(1 - ratio));
+	bool result_is_ok { };
 
-	return (closeness < tol);
+	if(fpc_b == FP_ZERO)
+	{
+		const floating_point_type closeness { (fpc_a == FP_ZERO) ? floating_point_type { 0 } : fabs(a - b) };
+
+		result_is_ok = (closeness < tol);
+	}
+	else
+	{
+		const floating_point_type ratio     = fabs(floating_point_type((floating_point_type(1) * a) / b));
+
+		const floating_point_type closeness = fabs(floating_point_type(1 - ratio));
+
+		result_is_ok = (closeness < tol);
+	}
+
+	return result_is_ok;
 }
 
 // N[Pi, 51]
@@ -108,7 +125,7 @@ auto cyl_bessel_j(const std::uint_fast8_t n, const FloatingPointType& x) noexcep
 	using std::sin;
 	using std::sqrt;
 
-	const auto tol = sqrt(epsilon);
+	const floating_point_type tol { sqrt(epsilon) };
 
 	const auto integration_result =
 	detail::integral
@@ -121,7 +138,7 @@ auto cyl_bessel_j(const std::uint_fast8_t n, const FloatingPointType& x) noexcep
 			return cos(x * sin(t) - (t * static_cast<floating_point_type>(n)));
 		});
 
-	const auto jn = static_cast<floating_point_type>(integration_result / detail::pi_v<floating_point_type>);
+	const floating_point_type jn { static_cast<floating_point_type>(integration_result / detail::pi_v<floating_point_type>) };
 
 	return jn;
 }
@@ -130,9 +147,9 @@ auto cyl_bessel_j(const std::uint_fast8_t n, const FloatingPointType& x) noexcep
 
 auto main() -> int
 {
-	using my_float_type = long double;
+	using my_float_type = std::float_t;
 
-	static_assert((std::numeric_limits<my_float_type>::digits >= 24), "Error: Incorrect my_float_type type definition");
+	static_assert((std::numeric_limits<my_float_type>::digits == 24), "Error: Incorrect my_float_type type definition");
 
 	constexpr my_float_type my_tol =
 		static_cast<my_float_type>

include/bits/stl_iterator.h

@@ -2150,6 +2150,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 		    const counted_iterator<_It2>& __y)
 	{ return __y._M_length <=> __x._M_length; }
 
+    private:
+      template<input_or_output_iterator _It2> friend class counted_iterator;
+
+      _It _M_current = _It();
+      iter_difference_t<_It> _M_length = 0;
+
       friend constexpr iter_rvalue_reference_t<_It>
       iter_move(const counted_iterator& __i)
       noexcept(noexcept(ranges::iter_move(__i._M_current)))
@@ -2162,12 +2168,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 		  const counted_iterator<_It2>& __y)
 	noexcept(noexcept(ranges::iter_swap(__x._M_current, __y._M_current)))
 	{ ranges::iter_swap(__x._M_current, __y._M_current); }
-
-    private:
-      template<input_or_output_iterator _It2> friend class counted_iterator;
-
-      _It _M_current = _It();
-      iter_difference_t<_It> _M_length = 0;
     };
 
   template<typename _It>

include/cmath

@@ -611,8 +611,46 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #undef islessgreater
 #undef isunordered
 
+#if !defined(FP_NAN) && !defined(FP_INFINITE) && !defined(FP_ZERO) \
+  && !defined(FP_SUBNORMAL) && !defined(FP_NORMAL)
+#define FP_NAN         0
+#define FP_INFINITE    1
+#define FP_ZERO        2
+#define FP_SUBNORMAL   3
+#define FP_NORMAL      4
+#elif !defined(FP_NAN) || !defined(FP_INFINITE) || !defined(FP_ZERO) \
+  || !defined(FP_SUBNORMAL) || !defined(FP_NORMAL)
+#error "Some floating-point number classification macros are missing."
+#error "Either define all of them or define none of them so that <cmath> can do it."
+#endif
+
 #if __cplusplus >= 201103L
 
+#ifndef __CORRECT_ISO_CPP11_MATH_H_PROTO_FP
+  constexpr int
+  fpclassify(float __x)
+  { return __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL,
+                               FP_SUBNORMAL, FP_ZERO, __x); }
+
+  constexpr int
+  fpclassify(double __x)
+  { return __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL,
+                               FP_SUBNORMAL, FP_ZERO, __x); }
+
+  constexpr int
+  fpclassify(long double __x)
+  { return __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL,
+                               FP_SUBNORMAL, FP_ZERO, __x); }
+#endif
+
+#ifndef __CORRECT_ISO_CPP11_MATH_H_PROTO_INT
+  template<typename _Tp>
+    constexpr typename __gnu_cxx::__enable_if<__is_integer<_Tp>::__value,
+                                              int>::__type
+    fpclassify(_Tp __x)
+    { return __x != 0 ? FP_NORMAL : FP_ZERO; }
+#endif
+
 #ifndef __CORRECT_ISO_CPP11_MATH_H_PROTO_FP
   constexpr bool
   isfinite(float __x)