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Unify Lua number to FFI integer conversions.

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Phew. #1411
This commit is contained in:
Mike Pall
2025-11-27 17:45:17 +01:00
parent 3215838aa7
commit f80b349d54
41 changed files with 1070 additions and 434 deletions
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60
doc/ext_ffi_semantics.html
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@@ -338,42 +338,44 @@ pointer or type compatibility:
<tr class="odd">
<td class="convin">Integer</td><td class="convop">&rarr;<sup>round</sup></td><td class="convout"><tt>double</tt>, <tt>float</tt></td></tr>
<tr class="even">
<td class="convin"><tt>double</tt>, <tt>float</tt></td><td class="convop">&rarr;<sup>trunc</sup> <tt>int32_t</tt> &rarr;<sup>narrow</sup></td><td class="convout"><tt>(u)int8_t</tt>, <tt>(u)int16_t</tt></td></tr>
<td class="convin"><tt>double</tt>, <tt>float</tt></td><td class="convop">&rarr;<sup>trunc</sup> <tt>int64_t</tt> &rarr;<sup>narrow</sup> <sup>*</sup></td><td class="convout"><tt>(u)int8_t</tt>, <tt>(u)int16_t</tt>, <tt>(u)int32_t</tt></td></tr>
<tr class="odd">
<td class="convin"><tt>double</tt>, <tt>float</tt></td><td class="convop">&rarr;<sup>trunc</sup></td><td class="convout"><tt>(u)int32_t</tt>, <tt>(u)int64_t</tt></td></tr>
<td class="convin"><tt>double</tt>, <tt>float</tt></td><td class="convop">&rarr;<sup>trunc</sup></td><td class="convout"><tt>int64_t</tt></td></tr>
<tr class="even">
<td class="convin"><tt>double</tt>, <tt>float</tt></td><td class="convop">&rarr;<sup>trunc</sup> uint64_t &cup; int64_t &rarr;<sup>reinterpret</sup> <sup>*</sup></td><td class="convout"><tt>uint64_t</tt></td></tr>
<tr class="odd">
<td class="convin"><tt>double</tt>, <tt>float</tt></td><td class="convop">&rarr;<sup>round</sup></td><td class="convout"><tt>float</tt>, <tt>double</tt></td></tr>
<tr class="odd separate">
<tr class="even separate">
<td class="convin">Number</td><td class="convop">n == 0 &rarr; 0, otherwise 1</td><td class="convout"><tt>bool</tt></td></tr>
<tr class="even">
<tr class="odd">
<td class="convin"><tt>bool</tt></td><td class="convop"><tt>false</tt> &rarr; 0, <tt>true</tt> &rarr; 1</td><td class="convout">Number</td></tr>
<tr class="odd separate">
<tr class="even separate">
<td class="convin">Complex number</td><td class="convop">convert real part</td><td class="convout">Number</td></tr>
<tr class="even">
<tr class="odd">
<td class="convin">Number</td><td class="convop">convert real part, imag = 0</td><td class="convout">Complex number</td></tr>
<tr class="odd">
<tr class="even">
<td class="convin">Complex number</td><td class="convop">convert real and imag part</td><td class="convout">Complex number</td></tr>
<tr class="even separate">
<tr class="odd separate">
<td class="convin">Number</td><td class="convop">convert scalar and replicate</td><td class="convout">Vector</td></tr>
<tr class="odd">
<tr class="even">
<td class="convin">Vector</td><td class="convop">copy (same size)</td><td class="convout">Vector</td></tr>
<tr class="even separate">
<tr class="odd separate">
<td class="convin"><tt>struct</tt>/<tt>union</tt></td><td class="convop">take base address (compat)</td><td class="convout">Pointer</td></tr>
<tr class="odd">
<tr class="even">
<td class="convin">Array</td><td class="convop">take base address (compat)</td><td class="convout">Pointer</td></tr>
<tr class="even">
<td class="convin">Function</td><td class="convop">take function address</td><td class="convout">Function pointer</td></tr>
<tr class="odd separate">
<td class="convin">Number</td><td class="convop">convert via <tt>uintptr_t</tt> (cast)</td><td class="convout">Pointer</td></tr>
<tr class="even">
<td class="convin">Pointer</td><td class="convop">convert address (compat/cast)</td><td class="convout">Pointer</td></tr>
<tr class="odd">
<td class="convin">Function</td><td class="convop">take function address</td><td class="convout">Function pointer</td></tr>
<tr class="even separate">
<td class="convin">Number</td><td class="convop">convert via <tt>uintptr_t</tt> (cast)</td><td class="convout">Pointer</td></tr>
<tr class="odd">
<td class="convin">Pointer</td><td class="convop">convert address (compat/cast)</td><td class="convout">Pointer</td></tr>
<tr class="even">
<td class="convin">Pointer</td><td class="convop">convert address (cast)</td><td class="convout">Integer</td></tr>
<tr class="even">
<tr class="odd">
<td class="convin">Array</td><td class="convop">convert base address (cast)</td><td class="convout">Integer</td></tr>
<tr class="odd separate">
<tr class="even separate">
<td class="convin">Array</td><td class="convop">copy (compat)</td><td class="convout">Array</td></tr>
<tr class="even">
<tr class="odd">
<td class="convin"><tt>struct</tt>/<tt>union</tt></td><td class="convop">copy (identical type)</td><td class="convout"><tt>struct</tt>/<tt>union</tt></td></tr>
</table>
<p>
@@ -384,6 +386,24 @@ type.
Conversions not listed above will raise an error. E.g. it's not
possible to convert a pointer to a complex number or vice versa.
</p>
<p>
* Some conversions from <tt>double</tt> have a larger defined range to
allow for mixed-signedness conversions, which are common in C code.
E.g. initializing an <tt>int32_t</tt> field with <tt>0xffffffff</tt>
or initializing an <tt>uint32_t</tt> or <tt>uint64_t</tt> field with
<tt>-1</tt>. Under strict conversion rules, these assignments would
give undefined results, since Lua numbers are doubles. The extended
ranges make these conversions defined. Lua numbers that are even
outside that range give an architecture-specific result.
</p>
<p>
Please note that doubles do not have the precision to represent the
whole signed or unsigned 64 bit integer range. Beware of large hex
constants in particular: e.g. <tt>0xffffffffffffffff</tt> is a double
rounded up to <tt>0x1p64</tt> during parsing. This will <em>not</em>
convert to a defined 64 bit integer value. Use the 64 bit literal
syntax instead, i.e. <tt>0xffffffffffffffffULL</tt>.
</p>
<h3 id="convert_vararg">Conversions for vararg C&nbsp;function arguments</h3>
<p>