Fix get_current_instruction_index

[LucasSte]

Problem

The function get_current_instruction_index was incorrectly implemented, returning the depth of the current executing instruction, not its index in trace. The issue was introduced in #9714.

Although get_current_instruction_context depended on it, the former was correctly using its results.

The other usage is in

agave/program-runtime/src/invoke_context.rs

Line 433 in 01159e4

let caller_index = self.transaction_context.get_current_instruction_index()?;

, but the index was there only for ABIv2 and had no real usage so far.

Summary of Changes

Implement the function correctly.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.2%. Comparing base (14b3d67) to head (e2831b9).
⚠️ Report is 12 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #10387   +/-   ##
=======================================
  Coverage    83.2%    83.2%           
=======================================
  Files         845      845           
  Lines      319794   319855   +61     
=======================================
+ Hits       266266   266350   +84     
+ Misses      53528    53505   -23     

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[buffalojoec]

Can you please add an explicit unit test that asserts get_current_instruction_index returns the correct trace index, especially for CPI scenarios where nesting_level != index_in_trace?

It's kinda covered by some existing tests, but something more direct and exhaustive would add some confidence here.

[nagisa]

Given that there is exactly one non-dead-code use of this function, why keep it at all?

[LucasSte]

Given that there is exactly one non-dead-code use of this function, why keep it at all?

TransactionContext is passed around as mutable and we don't want to expose the fields. Also, the dead-code usage will be live in a follow-up PR.

[LucasSte]

Can you please add an explicit unit test that asserts get_current_instruction_index returns the correct trace index, especially for CPI scenarios where nesting_level != index_in_trace?

It's kinda covered by some existing tests, but something more direct and exhaustive would add some confidence here.

Added a unit test in e2831b9.

[buffalojoec]

Added a unit test in e2831b9.

Thanks!!