"Assigning to invalid map proxy value" crash on OSX - endToEnd tutorial

[robpieke]

On OSX, after building USD with the customisations suggested in Issue 19, I get a crash partway through the endToEnd tutorial.

The create_asset.py script runs cleanly, but the add_shadingVariants.py script bails:

$ python tutorial_scripts/add_shadingVariants.py

(TfDiagnosticType)1: in _DefineCppType at line 868 of pxr//Users/robpieke/dev/github/USD/pxr/base/lib/tf/type.cpp -- TfType 'TfDebugSymbolsChangedNotice' already has a defined C++ type; cannot redefine
(TfDiagnosticType)1: in _DefineCppType at line 868 of pxr//Users/robpieke/dev/github/USD/pxr/base/lib/tf/type.cpp -- TfType 'TfDebugSymbolEnableChangedNotice' already has a defined C++ type; cannot redefine

Traceback (most recent call last):
File "tutorial_scripts/add_shadingVariants.py", line 133, in
main()
File "tutorial_scripts/add_shadingVariants.py", line 46, in main
_AddShadingToBall(stage)
File "tutorial_scripts/add_shadingVariants.py", line 89, in _AddShadingToBall
shadingVariant.SetVariantSelection(variantName)
pxr.Tf.ErrorException:
Error in '>::_Set' at line 822 in file pxr//Users/robpieke/dev/github/USD/build/include/pxr/usd/sdf/mapEditProxy.h : 'Assigning to invalid map proxy value'

Please note the "TfDiagnosticType" warnings at the top are the result of the patch from Issue 19. I get those every time I import the python modules. I include them for completeness, but it's the trace below which is concerning.

[jtran56]

Filed as internal issue #138602.

[drwave]

Hmm, so I have USD w/Python compiled on my macOS machine, and just ran through the tutorial. I do get the same last error, but I don't see the diagnostic you do. Did you apply the fix the workaround to your tree?

https://github.com/zhoub/USD/commit/67200e58a7a1df276bc4caca00c04fabcc63ceb5

python tutorial_scripts/add_shadingVariants.py
Traceback (most recent call last):
File "tutorial_scripts/add_shadingVariants.py", line 133, in
main()
File "tutorial_scripts/add_shadingVariants.py", line 46, in main
_AddShadingToBall(stage)
File "tutorial_scripts/add_shadingVariants.py", line 89, in _AddShadingToBall
shadingVariant.SetVariantSelection(variantName)
pxr.Tf.ErrorException:
Error in '>::_Set' at line 822 in file pxr//Users/wave/Projects/usd/stage/include/pxr/usd/sdf/mapEditProxy.h : 'Assigning to invalid map proxy value'
[kelvin:~/tests] wave%

[drwave]

Sorry, just read through issue 19 and realized that's where that fix I was referencing came from. What os release are you running?

[drwave]

Also, I just tried this (in the same directory) on a Linux box w/our standard USD build on it, and it ran to completion, so there definitely seems to be something fishy going on with the build on the mac.

Investigating...

[drwave]

Okay, here's a minimal piece of Python that demonstrates the problem on my Mac build but works fine on our standard USD build on Linux:

from pxr import Usd
stage = Usd.Stage.CreateNew("/tmp/foo.usda")
model = stage.OverridePrim('/Ball')
shadingVariant = model.GetVariantSets().FindOrCreate('shadingVariant')
shadingVariant.SetVariantSelection("Boom")
print "made it!"

[robpieke]

Glad I'm not the only sufferer :)

[drwave]

For those that want to dig a little deeper in C++, here's that code (giving the same error) transliterated into C++:

std::string path("/tmp/foo.usda");
UsdStageRefPtr stage = UsdStage::Open(path);
SdfPath primPath("/Ball");
UsdPrim prim = stage->OverridePrim(primPath);
UsdVariantSet shadingVariant = prim.GetVariantSets().FindOrCreate("shadingVariant");
// this next line generates a coding error on the Mac, but seems to work fine on Linux
// Coding Error: in _Set at line 822 of pxr//Users/wave/Projects/usd/stage/include/pxr/usd/sdf/mapEditProxy.h -- Assigning to invalid map proxy value
shadingVariant.SetVariantSelection("Boom");

[meshula]

Confirmed here as well.

[meshula]

A Debug build works properly. Release doesn't. Still investigating.

[sunyab]

I poked at this a little bit. In SdfMapEditProxy::_Get, we're comparing against a default-constructed std::map iterator as a safety check. It turns out this is undefined behavior; comparisons against a singular iterator are undefined per the C++ standard 24.1/5. A fix ought to be pretty straightforward.

[drwave]

That’s great news!

On Nov 4, 2016, at 10:28 AM, Sunya Boonyatera [email protected] wrote:

I poked at this a little bit. In SdfMapEditProxy::_Get, we're comparing against a default-constructed std::map iterator as a safety check. It turns out this is undefined behavior; comparisons against a singular iterator are undefined per the C++ standard 24.1/5. A fix ought to be pretty straightforward.

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[meshula]

Oh! Good find.