In VBA, there is a "fixed length" strings type [1], declared as

  Dim s As String * 123

which takes length argument up to 2^16, and makes the string length fixed to that value. Assigning a shorter string to it would pad spaces, and assigning a longer string would truncate.

In LibreOffice Basic, there was always a code to support that feature, not even dependent on the VBA support mode: the SbiSymDef::nLen member, the SbiOpcode::PAD_ (used in SbiParser::Assign), the respective SbiRuntime::StepPAD.

However, it has never worked properly. Before OOo 3.3, the declaration like above would create a 0-length string variable (while it must be 123-character from start, filled with spaces). Starting with OOo 3.3 (and LO), the declaration creates the correct string, but following assignments break that invariant:

  s = "abc"
  MsgBox Len(s) ' emits "3", instead if proper "123"

And using Let to assign the variable:

  Let s = "def"

even used to crash the process before version 4.0 (likely, commit 6702bc37d4bc28ec45c6c25f6a953997f6999270 helped to fix the incorrect cast into the variable internals, but at the same time, it broke the *idea* that the StepPAD function is intended to modify the value on stack, that will be assigned to the variable at the next StepPUT - the current code is basically a no-op, modifying a local variable that is never used).

Additionally, even the original idea was broken, because it (hoped to) directly modify the value, which might belong to another variable. *If* it worked, then a code like this:

  Dim s2 As String
  s2 = "gfh"
  MsgBox Len(s2) ' 3
  Let s = s2
  MsgBox Len(s2) ' would be 123 !!!

would suddenly make s2 equal to s, having the length of 123.

The code generator must emit the SbiOpcode::PAD_ also in SbiParser::Symbol (which handles assignments without Let keyword), and the runtime must take care to replace the variable on stack, when changing the length, instead of modifying the existing variable's value there.

[1] https://learn.microsoft.com/en-us/office/vba/language/reference/user-interface-help/string-data-type