[Flightgear-devel] SimGear bug? read-only properties tied to object methods not initialized
Hi all - here comes a tricky one:
(good bugs are usually tricky - not everything tricky is necessarily a bug)
Imagine an arbitrary PropertyList config file like this:
PropertyList
foo type=double3.14/foo
/PropertyList
and a code fragment like
class MyClass {
public:
double getter() const { return foo; }
void setter( double d ) { foo = d; }
void dosomethingfancy();
private:
double foo;
};
void MyClass::dosomethingfancy()
{
someBaseNode-tie( foo, this, MyClass:getter, MyClass::setter );
}
Ignore the fact, that it doesn't make much sense here - it's just an example.
One would expect that foo in MyClass (and the value of the thereafter tied
property) gets initialized to the value of foo from the config file which is
3.14. This actually works fine.
Now, modify the xml file to look like this:
PropertyList
foo type=double write=n3.14/foo
/PropertyList
(note: foo is now read-only)
The value of the foo-property now remains at an unchangeable value of zero, it
no longer gets initialized to the provided value in foo. That is because the
property is declared read-only and the setter method never gets called.
In simgear/props/props.hxx in SGPropertyNode::tie() some code exist to set the
value of a property after being tied, to the default value using setValue().
However, setValue() is smart enough to check for a read-only property and
refuses to change a property value in that case.
A fix might be to temporarily set the WRITE-flag for the property in the tie()
method like this:
(fragment from props.hxx, SGPropertyNode::tie(const SGRawValueT rawValue,
bool useDefault), line 1789ff
if (useDefault) {
int save_attributes = getAttributes(); // save current write-flag
setAttribute( WRITE, true ); // write-enable the property
setValue(old_val); // set the old value
setAttributes( save_attributes ); // restore write-flag
}
instead of
if (useDefault) {
setValue(old_val); // noop for read-only property
}
Comments?
Torsten
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[Flightgear-devel] Simgear Bug
Hello, I am trying to build simgear on Debian, but when I run make check in the simgear/math folder I get the following output included below. Is there something I can tweak to fix this bug? Thanks, Chris make SGMathTest SGGeometryTest make[1]: Entering directory `/home/chris/Packaging/Flightgear/SimgearDevPackage/Test Build/SimGear-2.0.0/simgear/math' g++ -DHAVE_CONFIG_H -I. -I../../simgear -I../..-g -O2 -D_REENTRANT -MT SGMathTest.o -MD -MP -MF .deps/SGMathTest.Tpo -c -o SGMathTest.o SGMathTest.cxx SGMathTest.cxx: In function ‘bool sgInterfaceTest()’: SGMathTest.cxx:259: error: ‘struct SGVec3f’ has no member named ‘sg’ SGMathTest.cxx:260: error: ‘struct SGVec3f’ has no member named ‘sg’ SGMathTest.cxx:268: error: ‘struct SGVec4f’ has no member named ‘sg’ SGMathTest.cxx:269: error: ‘struct SGVec4f’ has no member named ‘sg’ SGMathTest.cxx:277: error: ‘struct SGQuatf’ has no member named ‘sg’ SGMathTest.cxx:278: error: ‘struct SGQuatf’ has no member named ‘sg’ SGMathTest.cxx: In function ‘bool sgdInterfaceTest()’: SGMathTest.cxx:308: error: ‘struct SGVec3d’ has no member named ‘sg’ SGMathTest.cxx:309: error: ‘struct SGVec3d’ has no member named ‘sg’ SGMathTest.cxx:317: error: ‘struct SGVec4d’ has no member named ‘sg’ SGMathTest.cxx:318: error: ‘struct SGVec4d’ has no member named ‘sg’ SGMathTest.cxx:326: error: ‘struct SGQuatd’ has no member named ‘sg’ SGMathTest.cxx:327: error: ‘struct SGQuatd’ has no member named ‘sg’ make[1]: *** [SGMathTest.o] Error 1 make[1]: Leaving directory `/home/chris/Packaging/Flightgear/SimgearDevPackage/Test Build/SimGear-2.0.0/simgear/math' make: *** [check-am] Error 2 -- The Palm PDK Hot Apps Program offers developers who use the Plug-In Development Kit to bring their C/C++ apps to Palm for a share of $1 Million in cash or HP Products. Visit us here for more details: http://p.sf.net/sfu/dev2dev-palm ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Simgear Bug
On 29 Jul 2010, at 10:37, Chris Baines wrote: I am trying to build simgear on Debian, but when I run make check in the simgear/math folder I get the following output included below. Is there something I can tweak to fix this bug? 'make check' works in latest Git source, though I wasn't aware anything had changed in this area since 2.0 - slightly odd. I'd suggest you take a look at the git logs for simgear/math since 2.0.0, and if you can't find an obvious smoking gun, let me know. James -- The Palm PDK Hot Apps Program offers developers who use the Plug-In Development Kit to bring their C/C++ apps to Palm for a share of $1 Million in cash or HP Products. Visit us here for more details: http://p.sf.net/sfu/dev2dev-palm ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
