fix: iteration block hook injection [backport 3.9]

[github-actions]

Backport d7b62d5 from #13772 to 3.9.

We fix an issue with the instrumentation of the beginning of iteration blocks (e.g. for loops) whereby instrumenting the end might cause unexpected behaviour when the modified function is invoked. This is due to the bytecode VM not liking any bytecode interposed before the instruction that ends the iteration block (e.g. END_FOR). This also solves the problem of double-calls of the instrumented hook when hitting the beginning of such blocks.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

releasenotes/notes/fix-iteration-block-injection-af354b7004554dfd.yaml  @DataDog/apm-python
ddtrace/internal/bytecode_injection/__init__.py                         @DataDog/apm-core-python
tests/internal/bytecode_injection/test_injection.py                     @DataDog/apm-core-python

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 275 ± 3 ms.

The average import time from base is: 276 ± 2 ms.

The import time difference between this PR and base is: -1.7 ± 0.1 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 1.951 ms (0.71%)

ddtrace.bootstrap.sitecustomize 1.274 ms (0.46%)

ddtrace.bootstrap.preload 1.274 ms (0.46%)

ddtrace.internal.remoteconfig.client 0.627 ms (0.23%)

ddtrace 0.677 ms (0.25%)

ddtrace.internal._unpatched 0.031 ms (0.01%)

json 0.031 ms (0.01%)

json.decoder 0.031 ms (0.01%)

re 0.031 ms (0.01%)

enum 0.031 ms (0.01%)

types 0.031 ms (0.01%)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-06-30 14:09:03

Comparing candidate commit d883fbb in PR branch backport-13772-to-3.9 with baseline commit e0e451c in branch 3.9.

Found 0 performance improvements and 2 performance regressions! Performance is the same for 528 metrics, 2 unstable metrics.

scenario:iastaspects-format_map_aspect

• 🟥 execution_time [+515.681ns; +578.143ns] or [+15.816%; +17.731%]

scenario:iastaspectsospath-ospathsplitdrive_aspect

• 🟥 execution_time [+516.546ns; +582.514ns] or [+13.949%; +15.730%]