Batched shading crashes in `pointcloud_search()`

[johnhaddon]

Problem

Expected behavior: pointcloud_search() returns the same result in batched shading mode as in regular mode.

Actual behavior: pointcloud_search() crashes in batched shading mode with the following stack trace :

#0  0x00007fff312a32de in OSL_v1_12::b16_AVX512_noFMA_pvt::(anonymous namespace)::default_pointcloud_search(OSL_v1_12::BatchedShaderGlobals<16>*, OpenImageIO_v2_4::ustring, void const*, OSL_v1_12::Wide<float const, 16>, int, bool, OSL_v1_12::BatchedRendererServices<16>::PointCloudSearchResults&)::{lambda(OSL_v1_12::ActiveLane)#1}::operator()(OSL_v1_12::ActiveLane) const () from /home/john/dev/build/gaffer-1.3/lib/lib_b16_AVX512_noFMA_oslexec.so
#1  0x00007fff312a947f in osl_b16_AVX512_noFMA_pointcloud_search_masked () from /home/john/dev/build/gaffer-1.3/lib/lib_b16_AVX512_noFMA_oslexec.so
#2  0x00007fffd58002ad in ?? ()
#3  0x0000000000000001 in ?? ()
#4  0x0000000000000000 in ?? ()

Steps to Reproduce

1. Build OSL with the default Partio-based pointcloud services (I used Partio 1.14.6).
2. Write a shader that uses pointcloud_search() and run it in batched mode.

(These repro steps are a bit lame - I can probably come up with something more specific if the bug doesn't immediately jump out at you).

Versions

• OSL branch/version: 1.12.9
• OS: CentOS 7
• C++ compiler: GCC 9.3.1
• LLVM version: 11.1.0
• OIIO version: 2.4.11.0

[johnhaddon]

Did a bit more digging. The crash only occurs when not providing the "index" output array which the language docs imply is optional (and which can be omitted fine in non-batched mode), but which BatchedRendererServices claims is mandatory. The crash then occurs when writing via an invalid pointer in default_pointcloud_search().

So this is OK :

point points[5];
int indices[5];
pointcloud_search( filename, pW, 100, 5, 1, "position", points, "index", indices );

But this crashes :

point points[5];
pointcloud_search( filename, pW, 100, 5, 1, "position", points );

[lgritz]

@AlexMWells Can you take a look at this?

[AlexMWells]

I added an additional unit test and can confirm it does indeed crash:

#### Error: this command failed: 
2/2 Test #999: pointcloud.batched.opt ...........***Failed    3.47 sec
/bin/sh: line 1: 138828 Aborted                 (core dumped) testshade --center --vary_pdxdy -g 256 256 -t 1 -param radius 0.1 -od uint8 -o Cout out_rdcloud_varying_no_index.tif rdcloud_varying_no_index >> out.txt 2>> out.txt

I'll look at the implementation...

[AlexMWells]

I created https://github.com/AcademySoftwareFoundation/OpenShadingLanguage/pull/1753

to address the crash