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Parameter: resolve PolymorpicValue setup

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`PolymorphicValue` incurs some quite confusing requirements due to
the clumsy way how the instance handling and copy support must be injected.
As pointed out in #1197, with modern C++, this could be much simplified.

An overhaul of `PolymorphicValue` seems urgent thus -- in the meanwhile
we need to introduce more flexibiltiy with base-class template parameters,
so that we can inject the CopySupport interface at usage site of the
complete implementation class chain. Furthermore, the size of the VTable
is added automatically to the storage requirements in `PolymorphicValue`,
so we must subtract it when specifying the payload size by a compile-time
expression based on `sizeof(ParamData<double>)`

With these tweaks, we can now keep the limit of 4 «slots» (32 bytes)
and still reserve 64bit for ID and type flags.
This commit is contained in:
Fischlurch 2026-09-02 23:10:07 +02:00
parent 3d01ebf63c
commit ee629b56b7
4 changed files with 72 additions and 20 deletions
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12
src/lib/par/disposition.hpp
View file

@ -64,9 +64,9 @@ namespace par {
* with domain and scale, and a value provision. Can be generated through a builder * with domain and scale, and a value provision. Can be generated through a builder
* notation and stored within the Parameter object (as a container). * notation and stored within the Parameter object (as a container).
*/ */
template<typename VAL> template<typename VAL, class IFA =Disposition> /////////////////////////////////////////////////////TICKET #1197 : the second template argument is quite confusing and became necessary due to the limitations of PolymorphicValue
class ParamData class ParamData
: public TypedEntity<VAL, Disposition> : public TypedEntity<VAL, IFA>
{ {
VAL val_; VAL val_;
Provision* src_; Provision* src_;
@ -87,16 +87,16 @@ namespace par {
template<typename VAL> template<typename VAL, class IFA>
void void
ParamData<VAL>::retrieveInto (ValBuff& target) const ParamData<VAL, IFA>::retrieveInto (ValBuff& target) const
{ {
asValue<VAL>(target) = val_; asValue<VAL>(target) = val_;
} }
template<typename VAL> template<typename VAL, class IFA>
void void
ParamData<VAL>::setValFrom (ValBuff const& newVal) ParamData<VAL, IFA>::setValFrom (ValBuff const& newVal)
{ {
val_ = asValue<VAL>(newVal); val_ = asValue<VAL>(newVal);
} }

6
src/lib/par/parameter.hpp
View file

@ -40,10 +40,10 @@ namespace lib {
namespace par { namespace par {
namespace { namespace {
static constexpr size_t BUFF_SIZ = sizeof(ParamData<double>); static constexpr size_t PAYLOAD_SIZ = sizeof(ParamData<double>) - sizeof(void*); ////////////////////////TICKET #1197 : this is a mess! PolymorphicValue adds the ADMIN_OVERHEAD (but our payload has already a VTable)
using ParameterImplAPI = Disposition; using ParameterImplAPI = Disposition;
using CopySupportMarker = polyvalue::CopySupport<ParameterImplAPI>; using CopySupportMarker = polyvalue::CopySupport<ParameterImplAPI>;
using ParamContainer = PolymorphicValue<ParameterImplAPI, BUFF_SIZ, CopySupportMarker>; using ParamContainer = PolymorphicValue<ParameterImplAPI, PAYLOAD_SIZ, CopySupportMarker>;
} }
using util::unConst; using util::unConst;
@ -100,7 +100,7 @@ namespace par {
Parameter Parameter
build() build()
{ {
using ImplPackage = ParamData<VAL>; using ImplPackage = ParamData<VAL, CopySupportMarker>; //////////////////////////////////////////TICKET #1197 : remove the necessity to inject the CopySupportMarker
ImplPackage* typeTag{nullptr}; ImplPackage* typeTag{nullptr};
Parameter resParam{typeTag, std::move (initVal_)}; Parameter resParam{typeTag, std::move (initVal_)};
return resParam; return resParam;

5
tests/lib/par/parameter-test.cpp
View file

@ -77,12 +77,7 @@ namespace test{
void void
simpleUsage() simpleUsage()
{ {
SHOW_EXPR(BUFF_SIZ);
CHECK (sizeof(Parameter) <= 4 * sizeof(void*)); CHECK (sizeof(Parameter) <= 4 * sizeof(void*));
SHOW_EXPR(BaseTypeID<float>::value)
SHOW_EXPR(BaseTypeID<float*>::value)
ParamData<int> dip(55);
SHOW_EXPR(sizeof(dip))
Parameter par = Parameter::forType<int>().build(); Parameter par = Parameter::forType<int>().build();
CHECK (0 == par.getVal<int>()); CHECK (0 == par.getVal<int>());

69
wiki/thinkPad.ichthyo.mm
View file

@ -84071,9 +84071,9 @@
</html></richcontent> </html></richcontent>
<arrowlink COLOR="#931557" DESTINATION="ID_87627416" ENDARROW="Default" ENDINCLINATION="-273;3165;" ID="Arrow_ID_867915966" STARTARROW="None" STARTINCLINATION="289;-1009;"/> <arrowlink COLOR="#931557" DESTINATION="ID_87627416" ENDARROW="Default" ENDINCLINATION="-273;3165;" ID="Arrow_ID_867915966" STARTARROW="None" STARTINCLINATION="289;-1009;"/>
<icon BUILTIN="clanbomber"/> <icon BUILTIN="clanbomber"/>
<node BACKGROUND_COLOR="#e0ceaa" COLOR="#af020b" CREATED="1788301729827" ID="ID_18695637" MODIFIED="1788382908281" TEXT="erscheint zunehmend dringend..."> <node BACKGROUND_COLOR="#e0ceaa" COLOR="#af020b" CREATED="1788301729827" ID="ID_18695637" MODIFIED="1788386325808" TEXT="erscheint zunehmend dringend...">
<linktarget COLOR="#ff2137" DESTINATION="ID_18695637" ENDARROW="Default" ENDINCLINATION="1165;103;" ID="Arrow_ID_1244208579" SOURCE="ID_1978220833" STARTARROW="None" STARTINCLINATION="349;18;"/>
<linktarget COLOR="#ff2137" DESTINATION="ID_18695637" ENDARROW="Default" ENDINCLINATION="1165;103;" ID="Arrow_ID_635472113" SOURCE="ID_1100385220" STARTARROW="None" STARTINCLINATION="373;14;"/> <linktarget COLOR="#ff2137" DESTINATION="ID_18695637" ENDARROW="Default" ENDINCLINATION="1165;103;" ID="Arrow_ID_635472113" SOURCE="ID_1100385220" STARTARROW="None" STARTINCLINATION="373;14;"/>
<linktarget COLOR="#ff2137" DESTINATION="ID_18695637" ENDARROW="Default" ENDINCLINATION="1165;103;" ID="Arrow_ID_1244208579" SOURCE="ID_1978220833" STARTARROW="None" STARTINCLINATION="343;20;"/>
<font NAME="SansSerif" SIZE="11"/> <font NAME="SansSerif" SIZE="11"/>
</node> </node>
<node BACKGROUND_COLOR="#d2beaf" COLOR="#5c4d6e" CREATED="1788301751355" ID="ID_1968045723" MODIFIED="1788301772221" TEXT="in diesem (oder dem n&#xe4;chsten) VerticalSlice angehen"> <node BACKGROUND_COLOR="#d2beaf" COLOR="#5c4d6e" CREATED="1788301751355" ID="ID_1968045723" MODIFIED="1788301772221" TEXT="in diesem (oder dem n&#xe4;chsten) VerticalSlice angehen">
@ -84655,9 +84655,10 @@
</node> </node>
<node BACKGROUND_COLOR="#eef0c5" COLOR="#990000" CREATED="1788380554839" ID="ID_1101549379" MODIFIED="1788380577746" TEXT="Kompromi&#xdf;: ziehe einen ID-Record bereits in die Disposition"> <node BACKGROUND_COLOR="#eef0c5" COLOR="#990000" CREATED="1788380554839" ID="ID_1101549379" MODIFIED="1788380577746" TEXT="Kompromi&#xdf;: ziehe einen ID-Record bereits in die Disposition">
<icon BUILTIN="pencil"/> <icon BUILTIN="pencil"/>
<node BACKGROUND_COLOR="#fafe99" COLOR="#fa002a" CREATED="1788382780349" ID="ID_552546860" MODIFIED="1788382805575" TEXT="PolymorphicValue nicht optimal definiert"> <node BACKGROUND_COLOR="#c2b6c8" COLOR="#5b280f" CREATED="1788382780349" ID="ID_552546860" MODIFIED="1788386239896" TEXT="PolymorphicValue nicht optimal definiert">
<icon BUILTIN="broken-line"/> <icon BUILTIN="broken-line"/>
<node CREATED="1788301325125" ID="ID_1978220833" MODIFIED="1788383057351" TEXT="das mit dem CopySupport ist ein echtes Problem "> <icon BUILTIN="button_cancel"/>
<node CREATED="1788301325125" ID="ID_1978220833" MODIFIED="1788386325808" TEXT="das mit dem CopySupport ist ein echtes Problem ">
<richcontent TYPE="NOTE"><html> <richcontent TYPE="NOTE"><html>
<head/> <head/>
<body> <body>
@ -84669,9 +84670,65 @@
</p> </p>
</body> </body>
</html></richcontent> </html></richcontent>
<arrowlink COLOR="#ff2137" DESTINATION="ID_18695637" ENDARROW="Default" ENDINCLINATION="1165;103;" ID="Arrow_ID_1244208579" STARTARROW="None" STARTINCLINATION="343;20;"/> <arrowlink COLOR="#ff2137" DESTINATION="ID_18695637" ENDARROW="Default" ENDINCLINATION="1165;103;" ID="Arrow_ID_1244208579" STARTARROW="None" STARTINCLINATION="349;18;"/>
<icon BUILTIN="smiley-angry"/>
</node>
<node BACKGROUND_COLOR="#e0ceaa" COLOR="#690f14" CREATED="1788383059641" ID="ID_1688642617" MODIFIED="1788386316028" TEXT="das Marker-Template mu&#xdf; wirklich in der Kette liegen">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<body>
<p>
...ich hatte es zwar definiert und im Container-Typ angegeben &#8212; aber dann im konkreten API-Aufbau doch nicht eingeschleift (weil es da thematisch ja auch nicht hingeh&#246;rt, Grrrr)
</p>
</body>
</html>
</richcontent>
<icon BUILTIN="broken-line"/>
</node>
<node CREATED="1788384797381" ID="ID_1232714334" MODIFIED="1788386029574" TEXT="stimmt garnicht &#x27f6; es w&#xe4;hlt die optimale Variante">
<icon BUILTIN="idea"/>
<node CREATED="1788384925999" ID="ID_906034232" MODIFIED="1788384956844" TEXT="aber es schl&#xe4;gt den &quot;admin overhead&quot; blindlings oben drauf"/>
<node CREATED="1788384957654" ID="ID_799415187" MODIFIED="1788384990688" TEXT="aber wir verwenden einen sizeof &#x27f6; da ist die VTable bereits mit eingerechnet"/>
<node CREATED="1788384992694" ID="ID_1687522773" MODIFIED="1788385063843" TEXT="also ist auch das Konzept &#xbb;admin-overhead&#xab; in sich verworren (und &#xfc;berfl&#xfc;ssig)">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<body>
<p>
insofern dieses ganze clevere seitw&#228;rige Attachment &#252;berfl&#252;ssig ist;&#160; die einzige zwingende Voraussetzung ist, da&#223; wir eine VTable haben
</p>
</body>
</html>
</richcontent>
</node>
</node>
<node BACKGROUND_COLOR="#c8c0b6" COLOR="#435e98" CREATED="1788386034754" ID="ID_1268627911" MODIFIED="1788386341107" TEXT="L&#xf6;sung">
<icon BUILTIN="idea"/>
<node CREATED="1788386039641" ID="ID_477009340" MODIFIED="1788386053499" TEXT="zweites Template-Argument in ParamData">
<node CREATED="1788386057747" ID="ID_904631655" MODIFIED="1788386082344" TEXT="damit kann dann der Parameter (Container) hier das CopySupport-API injizieren"/>
<node CREATED="1788386085851" ID="ID_1295285894" MODIFIED="1788386098957" TEXT="und wir halten die Komplexit&#xe4;t nur an einer stelle"/>
</node>
<node BACKGROUND_COLOR="#e0ceaa" COLOR="#690f14" CREATED="1788386101665" ID="ID_93545182" MODIFIED="1788386217575" TEXT="mu&#xdf; die PAYLOAD_SIZE so definieren, da&#xdf; die VTable-size abgezogen wird">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<body>
<p>
weil PolymorphicValue da blindlings seinen ADMIN_OVERHEAD draufschl&#228;gt. Das ist ein sekund&#228;res Problem im API-Design &#8212; wenn das Marker-API und der &#187;workaround&#171; mit dem Mix-in nicht mehr gebraucht werden, dann f&#228;llt auch diese ganze Verwirrung hier weg (die mich jetzt viele Stunden gekostet hat)
</p>
</body>
</html>
</richcontent>
<icon BUILTIN="messagebox_warning"/>
</node>
</node>
<node COLOR="#338800" CREATED="1788386354314" ID="ID_1688624687" MODIFIED="1788386399854" TEXT="jetzt pa&#xdf;ts: sizeof(Parameter) &#x2261; 4 &#xab;slot&#xbb;">
<font NAME="SansSerif" SIZE="11"/>
</node> </node>
<node CREATED="1788383059641" ID="ID_1688642617" MODIFIED="1788383077961" TEXT="das Marker-Template mu&#xdf; wirklich in der Kette liegen"/>
</node> </node>
</node> </node>
</node> </node>