[CURA-9331] Check if all paths are empty in supposedly non-empty wall-path.

[rburema]

This caused randomized infill starts to misbehave, since a 'non-empty' path-vector could be chosen to start that had only empty paths within itself.

[github-actions]

Unit Test Results

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Results for commit 819d09e.

♻️ This comment has been updated with latest results.

[Ghostkeeper]

It's almost fixed! All models attached to this ticket work now, except for this one:
CCR10S_Alastor__-_Head(2).zip

This is the stack trace:

#0  0x000055555565bef6 in std::vector<cura::ExtrusionJunction, std::allocator<cura::ExtrusionJunction> >::operator[] (this=0x10, __n=0) at /usr/include/c++/9/bits/stl_vector.h:1043
#1  0x000055555564d29d in cura::FffGcodeWriter::processSingleLayerInfill (this=0x5555559d71c8 <cura::FffProcessor::instance+8>, storage=..., gcode_layer=..., mesh=..., extruder_nr=0, mesh_config=..., 
    part=...) at /home/ghostkeeper/Projects/CuraEngine/src/FffGcodeWriter.cpp:1779
#2  0x000055555564a8b1 in cura::FffGcodeWriter::processInfill (this=0x5555559d71c8 <cura::FffProcessor::instance+8>, storage=..., gcode_layer=..., mesh=..., extruder_nr=0, mesh_config=..., part=...)
    at /home/ghostkeeper/Projects/CuraEngine/src/FffGcodeWriter.cpp:1459
#3  0x000055555564a208 in cura::FffGcodeWriter::addMeshPartToGCode (this=0x5555559d71c8 <cura::FffProcessor::instance+8>, storage=..., mesh=..., extruder_nr=0, mesh_config=..., part=..., 
    gcode_layer=...) at /home/ghostkeeper/Projects/CuraEngine/src/FffGcodeWriter.cpp:1433
#4  0x0000555555649a48 in cura::FffGcodeWriter::addMeshLayerToGCode (this=0x5555559d71c8 <cura::FffProcessor::instance+8>, storage=..., mesh=..., extruder_nr=0, mesh_config=..., gcode_layer=...)
    at /home/ghostkeeper/Projects/CuraEngine/src/FffGcodeWriter.cpp:1403
#5  0x0000555555646371 in cura::FffGcodeWriter::processLayer (this=0x5555559d71c8 <cura::FffProcessor::instance+8>, storage=..., layer_nr=..., total_layers=158)
    at /home/ghostkeeper/Projects/CuraEngine/src/FffGcodeWriter.cpp:1032
#6  0x000055555563c390 in cura::FffGcodeWriter::<lambda(int)>::operator()(int) const (__closure=0x7fffffffd298, layer_nr=8) at /home/ghostkeeper/Projects/CuraEngine/src/FffGcodeWriter.cpp:150
#7  0x0000555555659829 in cura::MultipleProducersOrderedConsumer<cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(int)>, cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(cura::LayerPlan*)> >::produce(cura::MultipleProducersOrderedConsumer<cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(int)>, cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(cura::LayerPlan*)> >::lock_t &) (this=0x7fffffffd260, lock=...)
    at /home/ghostkeeper/Projects/CuraEngine/src/utils/ThreadPool.h:308
#8  0x00005555556594f6 in cura::MultipleProducersOrderedConsumer<cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(int)>, cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(cura::LayerPlan*)> >::worker(cura::MultipleProducersOrderedConsumer<cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(int)>, cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(cura::LayerPlan*)> >::lock_t &) (this=0x7fffffffd260, lock=...)
    at /home/ghostkeeper/Projects/CuraEngine/src/utils/ThreadPool.h:348
#9  0x0000555555659312 in cura::MultipleProducersOrderedConsumer<cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(int)>, cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(cura::LayerPlan*)> >::<lambda(cura::MultipleProducersOrderedConsumer<cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(int)>, cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(cura::LayerPlan*)> >::lock_t&)>::operator()(cura::MultipleProducersOrderedConsumer<cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(int)>, cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(cura::LayerPlan*)> >::lock_t &) const (
    this=0x7fffffffd260, th_lock=...) at /home/ghostkeeper/Projects/CuraEngine/src/utils/ThreadPool.h:267
#10 0x0000555555659e44 in std::_Function_handler<void(std::unique_lock<std::mutex>&), cura::MultipleProducersOrderedConsumer<Producer, Consumer>::run(cura::ThreadPool&) [with Producer = cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(int)>; Consumer = cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(cura::LayerPlan*)>]::<lambda(cura::MultipleProducersOrderedConsumer<cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(int)>, cura::FffGcodeWriter::writeGCode(cura::SliceDataStorage&, cura::TimeKeeper&)::<lambda(cura::LayerPlan*)> >::lock_t&)> >::_M_invoke(const std::_Any_data &, std::unique_lock<std::mutex> &) (__functor=..., __args#0=...) at /usr/include/c++/9/bits/std_function.h:300
#11 0x0000555555600ed1 in std::function<void (std::unique_lock<std::mutex>&)>::operator()(std::unique_lock<std::mutex>&) const (this=0x7fffefffecf0, __args#0=...)
    at /usr/include/c++/9/bits/std_function.h:688
#12 0x0000555555600313 in cura::ThreadPool::work_while<cura::ThreadPool::worker()::<lambda()> >(cura::ThreadPool::lock_t &, cura::ThreadPool::<lambda()>) (this=0x5555559fcf00, lock=..., predicate=...)
    at /home/ghostkeeper/Projects/CuraEngine/src/utils/ThreadPool.h:70
#13 0x0000555555600044 in cura::ThreadPool::worker (this=0x5555559fcf00) at /home/ghostkeeper/Projects/CuraEngine/src/utils/ThreadPool.cpp:21
#14 0x0000555555602786 in std::__invoke_impl<void, void (cura::ThreadPool::*)(), cura::ThreadPool*> (
    __f=@0x5555559f8570: (void (cura::ThreadPool::*)(cura::ThreadPool * const)) 0x5555555fffec <cura::ThreadPool::worker()>, __t=@0x5555559f8568: 0x5555559fcf00) at /usr/include/c++/9/bits/invoke.h:73
#15 0x00005555556026b4 in std::__invoke<void (cura::ThreadPool::*)(), cura::ThreadPool*> (
    __fn=@0x5555559f8570: (void (cura::ThreadPool::*)(cura::ThreadPool * const)) 0x5555555fffec <cura::ThreadPool::worker()>) at /usr/include/c++/9/bits/invoke.h:95
#16 0x0000555555602613 in std::thread::_Invoker<std::tuple<void (cura::ThreadPool::*)(), cura::ThreadPool*> >::_M_invoke<0ul, 1ul> (this=0x5555559f8568) at /usr/include/c++/9/thread:244
#17 0x00005555556025ca in std::thread::_Invoker<std::tuple<void (cura::ThreadPool::*)(), cura::ThreadPool*> >::operator() (this=0x5555559f8568) at /usr/include/c++/9/thread:251
#18 0x00005555556025aa in std::thread::_State_impl<std::thread::_Invoker<std::tuple<void (cura::ThreadPool::*)(), cura::ThreadPool*> > >::_M_run (this=0x5555559f8560) at /usr/include/c++/9/thread:195
#19 0x00007ffff7694de4 in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#20 0x00007ffff77a8609 in start_thread (arg=<optimized out>) at pthread_create.c:477
#21 0x00007ffff737f133 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

From the code in question:

            else //So walls_generated must be true.
            {
                std::vector<VariableWidthLines>* start_paths = &wall_tool_paths[rand() % wall_tool_paths.size()];
                while(start_paths->empty()) //We know for sure (because walls_generated) that one of them is not empty. So randomise until we hit it. Should almost always be very quick.
                {
                    start_paths = &wall_tool_paths[rand() % wall_tool_paths.size()];
                }
                near_start_location = (*start_paths)[0][0].junctions[0].p;
            }

The issue seems to be with this:

(gdb) print (*start_paths)[0]
$1 = std::vector of length 0, capacity 0

I think I have a solution for this, so I'll commit that shortly.