0001179: Fix null context crash in ShapeUpgrade_FaceDivide::Perform()

[gsdali]

Issue

Fixes #1179

Problem

ShapeUpgrade_FaceDivide::Perform() crashes with a null pointer dereference in SplitCurves() at Context()->Apply() because myContext is never initialized.

ShapeUpgrade_FaceDivide inherits from ShapeUpgrade_Tool, which does not allocate a default ShapeBuild_ReShape context. The sibling class ShapeUpgrade_ShapeDivide handles this correctly with lazy initialization in its own Perform():

// ShapeUpgrade_ShapeDivide::Perform() — line 120-121
if (newContext || myContext.IsNull())
    myContext = new ShapeBuild_ReShape;

But ShapeUpgrade_FaceDivide::Perform() has no such guard.

Crash details

• Crash site: ShapeUpgrade_FaceDivide::SplitCurves() + 168 — KERN_INVALID_ADDRESS at 0x0
• Reproduces single-threaded (100% crash rate)
• Reproduces on Windows x64 (MSVC 19.44) and macOS arm64 (Apple Clang 21)
• Reproducer: https://github.com/gsdali/OCCTSwift/blob/main/Tests/occt_parallel_crash_portable.cpp
• Windows CI: https://github.com/gsdali/OCCTSwift/actions/runs/24509869728

Fix

Add lazy context initialization at the top of Perform(), matching the pattern used by ShapeUpgrade_ShapeDivide:

if (Context().IsNull())
    SetContext(new ShapeBuild_ReShape);

Verification

• Single-threaded: was crashing, now passes (100 iterations)
• Parallel (10 worker threads, 300 tasks/round, 10 rounds = 33,000 operations): was crashing 100%, now passes 5/5 runs
• All 11 isolated operation groups pass, plus combined test

[dpasukhi]

Dear @gsdali

Thank you for your patch. To proceed with integration, please complete signing CLA process:
The links: Contribution Guide
Or https://dev.opencascade.org/get_involved
Please validate the filled fields, all fields are requiered, only with exception if written (optional).

In case if you already have signed CLA, please share ID that OCCT team shared with your by email after accepting of CLA.

After CLA I will review your code and update the PR. I will clean up comments, remove the QA test and move that test into GTest(C++), not DRAW.

[gsdali]

License agreement submitted. Many Thanks,

…

-- Edward Lynch-Bell http://www.linkedin.com/in/edlynchbell/ +61 490 375 565

On Apr 17, 2026 at 16:38 +1000, Pasukhin Dmitry ***@***.***>, wrote: dpasukhi left a comment (Open-Cascade-SAS/OCCT#1203) Dear @gsdali Thank you for your patch. To proceed with integration, please complete signing CLA process: The links: Contribution Guide Or https://dev.opencascade.org/get_involved Please validate the filled fields, all fields are requiered, only with exception if written (optional). In case if you already have signed CLA, please share ID that OCCT team shared with your by email after accepting of CLA. After CLA I will review your code and update the PR. I will clean up comments, remove the QA test and move that test into GTest(C++), not DRAW. — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you were mentioned.Message ID: ***@***.***>