Fix Clang 10 -Werror,-Wimplicit-int-float-conversion

> idlc/source/astexpression.cxx:330:68: error: implicit conversion from 'sal_Int32' (aka 'int') to 'float' changes value from 2147483647 to 2147483648 [-Werror,-Wimplicit-int-float-conversion]
>                     if (ev->u.fval < SAL_MIN_INT32 || ev->u.fval > SAL_MAX_INT32)
>                                                                  ~ ^~~~~~~~~~~~~
> include/sal/types.h:209:32: note: expanded from macro 'SAL_MAX_INT32'
> #define SAL_MAX_INT32         ((sal_Int32)  0x7FFFFFFF)
>                                ^~~~~~~~~~~~~~~~~~~~~~~
> idlc/source/astexpression.cxx:414:58: error: implicit conversion from 'sal_uInt32' (aka 'unsigned int') to 'float' changes value from 4294967295 to 4294967296 [-Werror,-Wimplicit-int-float-conversion]
>                     if (ev->u.fval < 0.0 || ev->u.fval > SAL_MAX_UINT32)
>                                                        ~ ^~~~~~~~~~~~~~
> include/sal/types.h:210:32: note: expanded from macro 'SAL_MAX_UINT32'
> #define SAL_MAX_UINT32        ((sal_uInt32) 0xFFFFFFFF)
>                                ^~~~~~~~~~~~~~~~~~~~~~~
> idlc/source/astexpression.cxx:492:68: error: implicit conversion from 'sal_Int64' (aka 'long') to 'float' changes value from 9223372036854775807 to 9223372036854775808 [-Werror,-Wimplicit-int-float-conversion]
>                     if (ev->u.fval < SAL_MIN_INT64 || ev->u.fval > SAL_MAX_INT64)
>                                                                  ~ ^~~~~~~~~~~~~
> include/sal/types.h:212:32: note: expanded from macro 'SAL_MAX_INT64'
> #define SAL_MAX_INT64         ((sal_Int64)  SAL_CONST_INT64(0x7FFFFFFFFFFFFFFF))
>                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> idlc/source/astexpression.cxx:501:68: error: implicit conversion from 'sal_Int64' (aka 'long') to 'double' changes value from 9223372036854775807 to 9223372036854775808 [-Werror,-Wimplicit-int-float-conversion]
>                     if (ev->u.dval < SAL_MIN_INT64 || ev->u.dval > SAL_MAX_INT64)
>                                                                  ~ ^~~~~~~~~~~~~
> include/sal/types.h:212:32: note: expanded from macro 'SAL_MAX_INT64'
> #define SAL_MAX_INT64         ((sal_Int64)  SAL_CONST_INT64(0x7FFFFFFFFFFFFFFF))
>                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> idlc/source/astexpression.cxx:574:58: error: implicit conversion from 'sal_uInt64' (aka 'unsigned long') to 'float' changes value from 18446744073709551615 to 18446744073709551616 [-Werror,-Wimplicit-int-float-conversion]
>                     if (ev->u.fval < 0.0 || ev->u.fval > SAL_MAX_UINT64)
>                                                        ~ ^~~~~~~~~~~~~~
> include/sal/types.h:213:32: note: expanded from macro 'SAL_MAX_UINT64'
> #define SAL_MAX_UINT64        ((sal_uInt64) SAL_CONST_UINT64(0xFFFFFFFFFFFFFFFF))
>                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> idlc/source/astexpression.cxx:583:58: error: implicit conversion from 'sal_uInt64' (aka 'unsigned long') to 'double' changes value from 18446744073709551615 to 18446744073709551616 [-Werror,-Wimplicit-int-float-conversion]
>                     if (ev->u.dval < 0.0 || ev->u.dval > SAL_MAX_UINT64)
>                                                        ~ ^~~~~~~~~~~~~~
> include/sal/types.h:213:32: note: expanded from macro 'SAL_MAX_UINT64'
> #define SAL_MAX_UINT64        ((sal_uInt64) SAL_CONST_UINT64(0xFFFFFFFFFFFFFFFF))
>                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Consitently use the new o3tl::convertsToAtLeast/Most(o3tl::roundAway(...), ...)
for all cases in coerce_value that check that a floating-point value falls into
an integer range, even those that don't cause a warning.

The new idlc/test/parser/conversion.tests is deliberately left out of
unoidl/CustomTarget_unoidl-write_test.mk. as unoidl-write doesn't support such
conversions from floating-point to integer types.

Change-Id: Ie00923e665f2bcb306e1e328614c75b9247512ee
Reviewed-on: https://gerrit.libreoffice.org/77353
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/include/o3tl/float_int_conversion.hxx b/include/o3tl/float_int_conversion.hxx
new file mode 100644
index 000000000000..dfaea5ce3bd2
--- /dev/null
+++ b/include/o3tl/float_int_conversion.hxx
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_O3TL_FLOAT_INT_CONVERSION_HXX
+#define INCLUDED_O3TL_FLOAT_INT_CONVERSION_HXX
+
+#include <sal/config.h>
+
+#include <cmath>
+#include <type_traits>
+
+namespace o3tl
+{
+// Return true iff `value` of floating-point type `F` converts to a value of integral type `I` no
+// smaller than `min`:
+template <typename F, typename I>
+std::enable_if_t<std::is_floating_point_v<F> && std::is_integral_v<I>, bool>
+convertsToAtLeast(F value, I min)
+{
+    // If `F(min)`, `F(min) - F(1)` are too large in magnitude for `F`'s precision, then they either
+    // fall into the same bucket, in which case we should return false if `value` represents that
+    // bucket, or they are on the boundary of two adjacent buckets, in which case we should return
+    // true if `value`represents the higher bucket containing `F(min)`:
+    return value > F(min) - F(1);
+}
+
+// Return true iff `value` of floating-point type `F` converts to a value of integral type `I` no
+// larger than `max`:
+template <typename F, typename I>
+std::enable_if_t<std::is_floating_point_v<F> && std::is_integral_v<I>, bool>
+convertsToAtMost(F value, I max)
+{
+    // If `F(max)`, `F(max) + F(1)` are too large in magnitude for `F`'s precision, then they either
+    // fall into the same bucket, in which case we should return false if `value` represents that
+    // bucket, or they are on the boundary of two adjacent buckets, in which case we should return
+    // true if `value`represents the lower bucket containing `F(max)`:
+    return value < F(max) + F(1);
+}
+
+// Return `value` of floating-point type `F` rounded to the nearest integer away from zero (which
+// can be useful in calls to convertsToAtLeast/Most(roundAway(x), n), to reject x that are
+// smaller/larger than n because they have a fractional part):
+template <typename F> std::enable_if_t<std::is_floating_point_v<F>, F> roundAway(F value)
+{
+    return value >= 0 ? std::ceil(value) : std::floor(value);
+}
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */