inst->attributes[ ] and inst->NextAttribute( ) behave differently

[mpictor]

The first loop prints gibberish, while the second loop works.

        SDAI_Application_instance* inst = //...

        for (int j=0; j<inst->AttributeCount(); j++) {
            STEPattribute attr = inst->attributes[j];
            attr.asStr(value);
            cout << " ATT: " << attr.Name() << "  " << value << endl;
        }
        STEPattribute * attr;
        while(  attr = inst->NextAttribute()  ) {
            attr->asStr( value );
            cout << " ATT: " << attr->Name() << "  " << value << endl;
        }

[brlcad]

Possibly because inst->attributes[] has unset/NULL attribute members. The first loop doesn't care and ends up calling the copy constructor on unset/NULL, giving bogus values (easily possible if copy constructor isn't defined properly). I'm guessing the second loop encounters the NULL pointer and aborts all subsequent (potentially non-NULL) attributes.

Combining the best of both, this might detect that situation

for (int j=0; j<inst->AttributeCount(); j++) {
    STEPattribute *attr = inst->attributes[j];
    if (!attr)
        cout << "UNEXPECTED NULL ATTRIBUTE ENCOUNTERED" << endl;
    attr->asStr(value);
    cout << "  ATT: " << attr->Name() << "  " << value << endl;
}

[mpictor]

I've created an example where the order doesn't matter. However, it doesn't read from a file; that could be why it behaves correctly.

//must be linked with libsdai_AP214E3_2010
#define for_first

#include <sstream>
#include <sc_cf.h>
extern void SchemaInit( class Registry & );
#include <STEPfile.h>
#include <sdai.h>
#include <STEPattribute.h>
#include <ExpDict.h>
#include <Registry.h>
#include <errordesc.h>
#include "sc_version_string.h"

int main( int argc, char * argv[] ) {

    Registry  registry( SchemaInit );
    InstMgr   instance_list;
    STEPfile  sfile( registry, instance_list, "", true );
    std::stringstream str;
//     str << "#2 = APPLICATION_CONTEXT";
    str << "('core data for automotive mechanical design processes');" << std::endl;


    std::string value;

    SDAI_Application_instance* inst = registry.ObjCreate( "APPLICATION_CONTEXT",
        "AUTOMOTIVE_DESIGN" );
    inst->STEPread( 2, 0, &instance_list, str, "AUTOMOTIVE_DESIGN", true, false );
    inst->STEPwrite(cout);

    inst->ResetAttributes(); // NextAttribute() doesn't work correctly otherwise

    STEPattribute * attr, *at, a;
    STEPattributeList sal = inst->attributes;

#ifdef for_first
    for (int j=0; j<inst->AttributeCount(); j++) {
        a = sal[j];
        a.asStr(value);
        cout << " ATT: " << a.Name() << "  " << value << endl;
    }
#endif

    while(  attr = inst->NextAttribute()  ) {
        attr->asStr( value );
        cout << " ATT: " << attr->Name() << "  " << value << endl;
    }

#ifndef for_first
    for (int j=0; j<inst->AttributeCount(); j++) {
        a = sal[j];
        a.asStr(value);
        cout << " ATT: " << a.Name() << "  " << value << endl;
    }
#endif

    return 0;
}

output:

#2=APPLICATION_CONTEXT('core data for automotive mechanical design processes');
 ATT: application  'core data for automotive mechanical design processes'
 ATT: application  'core data for automotive mechanical design processes'

[mpictor]

I think I found the problem.

#include <sc_cf.h>
extern void SchemaInit( class Registry & );
#include <STEPfile.h>
#include <sdai.h>
#include <STEPattribute.h>
#include <ExpDict.h>
#include <Registry.h>

int main( int argc, char * argv[] ) {
    std::string value = "";
    Registry  registry( SchemaInit );
    InstMgr   instance_list;
    STEPfile  sfile( registry, instance_list, "", true );

    //use test_214.stp or data/ap214e3/s1-c5-214/HEAD.stp
    sfile.ReadExchangeFile( argv[1] );

    SDAI_Application_instance* inst = instance_list.GetSTEPentity(0);
    STEPattribute * at;

    inst->ResetAttributes(); // NextAttribute() doesn't work correctly otherwise
    while(  at = inst->NextAttribute()  ) {
        at->asStr( value );
        cout << "using NextAttribute: " << at->Name() << "  " << value << endl;
    }

    for (int j=0; j<inst->AttributeCount(); j++) {
        STEPattribute * att = &(inst->attributes[j]);
        att->asStr(value);
        cout << "using &(inst->attributes[j]): " << att->Name() << "  " << value << endl;
    }

    //first two work, but this one fails
    for (int j=0; j<inst->AttributeCount(); j++) {
        STEPattribute attr = inst->attributes[j];
        attr.asStr(value);
        cout << "using inst->attributes[j]: " << attr.Name() << "  " << value << endl;
    }

    return 0;
}

The third loop produces garbage unless the STEPattribute copy constructor is changed:

STEPattribute::STEPattribute( const STEPattribute & a )
-    : _derive( 0 ), _redefAttr( 0 ), aDesc( a.aDesc ), refCount( 0 ) {}
+    : _derive( a._derive ), _redefAttr( a._redefAttr ), aDesc( a.aDesc ), refCount( 0 ), ptr( a.ptr ) {}

However, this doesn't copy the contents of ptr - it is now shared between two different STEPattributes.