12.0 - Low-level Error: Free varnode has multiple descendants

[RealKindOne]

Describe the bug

I get a Low-level Error: Free varnode has multiple descendants error message in the Decompile window.

I do not get this error in 11.4.3.

To Reproduce
Steps to reproduce the behavior:

1. Create Project.
2. Import mirc-7.00.exe
3. Analysis
4. In Analysis Options select Standard Defaults
5. Analyze
6. Wait for it to complete.
7. Goto FUN_00441f40

Expected behavior
Show decompiled code.

Screenshots

Attachments

mirc-7.00.exe.zip

Environment (please complete the following information):

• OS: Windows 7 SP1
• Java Version: Adoptium Temurin JDK 21.0.4
• Ghidra Version: 12.0
• Ghidra Origin: GitHub distro

Additional context

This was found by using AddProgramToH2BSimDatabaseScript.java script.

[jobermayr]

Possible fix:

diff --git a/Ghidra/Features/Decompiler/src/decompile/cpp/funcdata_op.cc b/Ghidra/Features/Decompiler/src/decompile/cpp/funcdata_op.cc
index 489d45f3d3..e08ac21b87 100644
--- a/Ghidra/Features/Decompiler/src/decompile/cpp/funcdata_op.cc
+++ b/Ghidra/Features/Decompiler/src/decompile/cpp/funcdata_op.cc
@@ -105,7 +105,7 @@ void Funcdata::opSetInput(PcodeOp *op,Varnode *vn,int4 slot)
 
 {
   if (vn == op->getIn(slot)) return; // Already set to this vn
-  if (vn->isConstant()) {      // Constants should have only one descendant
+  if (vn->isConstant() || vn->isFree()) {      // Constants should have only one descendant
     if (!vn->hasNoDescend())
       if (!vn->isSpacebase()) {        // Unless they are a spacebase
        Varnode *cvn = newConstant(vn->getSize(),vn->getOffset());

[RealKindOne]

@jobermayr I compiled the Ghidra_12.0_build release with your patch and it works.

Compiled on Debian 13, gcc 14.2.0, gradle 9.2.1, openjdk-21

Screenshot: (x11 forward'ed from Debian to Windows)

[Piggo4676]

Wait sorry I'm getting the same issue, I'm decompiling a relatively large function and it gives me the error Low-level Error: Free varnode has multiple descendants almost instantly. It worked on version 11.3.2_PUBLIC20250415 but now it doesn't... I saw the fix thing there, but I don't know quite where you want me to put that and all that... Sorry if this is a stupid question...