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Raise OverflowError for float overflow in struct packing - #8360

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youknowone merged 1 commit into
RustPython:mainfrom
moreal:struct-float-overflow-in-packing
Jul 25, 2026
Merged

youknowone merged 1 commit into
RustPython:mainfrom
moreal:struct-float-overflow-in-packing

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@moreal

@moreal moreal commented Jul 24, 2026

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Summary

  • Detect when a finite Python float overflows to infinity while being converted for the struct f format.
  • Raise OverflowError with the CPython-compatible message instead of silently packing an IEEE 754 infinity.

Behavior changes

Before:

$ cargo run -- -c 'import math, struct; x = math.ldexp((1 << 25) - 1, 127 - 24); print(struct.pack(">f", x))'
b'\x7f\x80\x00\x00'

After:

$ cargo run -- -c 'import math, struct; x = math.ldexp((1 << 25) - 1, 127 - 24); print(struct.pack(">f", x))'
OverflowError: float too large to pack with f format

References

Summary by CodeRabbit

  • Bug Fixes
    • Improved detection of floating-point values that exceed the selected packing format’s representational limits.
    • Updated overflow messages to identify the affected float format, making errors clearer when packing values fails.

Raise OverflowError when a finite f64 value overflows while being converted for the struct f format. Remove the expected-failure marker from the corresponding regression test.

Assisted-by: Codex:gpt-5
@coderabbitai

coderabbitai Bot commented Jul 24, 2026

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Review Change Stack

📝 Walkthrough

Walkthrough

Float packing now preserves the parsed f_64 value for overflow detection, reports the target format in errors, and supplies format identifiers for f32 and f64.

Changes

Float packing

Layer / File(s) Summary
Float packing overflow handling
crates/vm/src/buffer.rs
make_pack_float compares infinity status before and after casting, formats overflow errors with the target type, and receives "f" or "d" at its invocations.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: bschoenmaeckers

🚥 Pre-merge checks | ✅ 5
✅ Passed checks (5 passed)
Check name Status Explanation
Docstring Coverage ✅ Passed No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title clearly matches the main change: raising OverflowError when struct packing overflows a float.
✨ Finishing Touches
🧪 Generate unit tests (beta)
  • Create PR with unit tests

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📦 Library Dependencies

The following Lib/ modules were modified. Here are their dependencies:

[x] lib: cpython/Lib/email
[ ] test: cpython/Lib/test/test_email (TODO: 12)

dependencies:

  • email

dependent tests: (53 tests)

  • email: test_email test_http_cookiejar test_httpservers test_mailbox test_smtplib test_urllib test_urllib2 test_urllib2_localnet test_urllibnet test_zipfile
    • http.client: test_docxmlrpc test_hashlib test_ssl test_ucn test_unicodedata test_wsgiref test_xmlrpc
      • logging.handlers: test_concurrent_futures test_logging test_pkgutil
      • urllib.request: test_pathlib test_pydoc test_sax test_site test_urllib2net
    • http.server: test_robotparser
      • pydoc: test_enum
    • importlib.metadata: test_importlib test_zoneinfo
    • mailbox: test_genericalias
    • pydoc:
      • pdb: test_pdb
    • smtplib: test_smtpnet
    • urllib.request:
      • pathlib: test_ast test_dbm_sqlite3 test_ensurepip test_importlib test_json test_launcher test_pathlib test_peg_generator test_pyrepl test_runpy test_tarfile test_tempfile test_tomllib test_tools test_traceback test_unparse test_venv test_winapi test_zipapp test_zipfile test_zstd

[x] lib: cpython/Lib/shlex.py
[x] test: cpython/Lib/test/test_shlex.py (TODO: 4)

dependencies:

  • shlex

dependent tests: (10 tests)

  • shlex: test_mimetypes test_random test_regrtest test_shlex test_venv test_webbrowser
    • pdb: test_pdb
    • webbrowser:
      • pydoc: test_enum test_pydoc
      • wsgiref.simple_server: test_wsgiref

[x] lib: cpython/Lib/weakref.py
[x] lib: cpython/Lib/_weakrefset.py
[x] test: cpython/Lib/test/test_weakref.py (TODO: 12)
[x] test: cpython/Lib/test/test_weakset.py

dependencies:

  • weakref

dependent tests: (222 tests)

  • weakref: test_array test_ast test_asyncio test_code test_concurrent_futures test_context test_contextlib test_copy test_ctypes test_deque test_descr test_dict test_enum test_exceptions test_file test_fileio test_finalization test_frame test_functools test_gc test_generators test_genericalias test_importlib test_inspect test_io test_ipaddress test_itertools test_logging test_memoryio test_memoryview test_mmap test_ordered_dict test_pickle test_picklebuffer test_queue test_re test_scope test_set test_slice test_socket test_sqlite3 test_ssl test_struct test_sys test_tempfile test_thread test_threading test_threading_local test_type_params test_types test_typing test_unittest test_uuid test_weakref test_weakset test_xml_etree
    • asyncio: test_asyncio test_external_inspection test_os test_pdb test_unittest
    • bdb: test_bdb
    • concurrent.futures.process: test_compileall test_concurrent_futures
    • copy: test_bytes test_codecs test_collections test_copyreg test_coroutines test_csv test_decimal test_defaultdict test_dictviews test_email test_fractions test_http_cookies test_minidom test_opcache test_optparse test_platform test_plistlib test_posix test_site test_statistics test_structseq test_super test_sysconfig test_tomllib test_urllib2 test_xml_dom_minicompat test_zlib
      • argparse: test_argparse
      • collections: test_annotationlib test_bisect test_builtin test_c_locale_coercion test_call test_configparser test_contains test_ctypes test_embed test_exception_group test_fileinput test_funcattrs test_hash test_httpservers test_iter test_iterlen test_json test_math test_monitoring test_pathlib test_patma test_pprint test_pydoc test_random test_reprlib test_richcmp test_shelve test_sqlite3 test_string test_traceback test_tuple test_urllib test_userdict test_userlist test_userstring test_with
      • dataclasses: test__colorize test_ctypes test_regrtest test_zoneinfo
      • email.generator: test_email
      • gettext: test_gettext test_tools
      • http.cookiejar: test_http_cookiejar
      • http.server: test_robotparser test_urllib2_localnet test_xmlrpc
      • logging.handlers: test_pkgutil
      • mailbox: test_mailbox
      • smtplib: test_smtplib test_smtpnet
      • tarfile: test_shutil test_tarfile
      • webbrowser: test_webbrowser
    • inspect: test_abc test_asyncgen test_buffer test_clinic test_grammar test_ntpath test_operator test_posixpath test_signal test_turtle test_type_annotations test_yield_from test_zipimport test_zipimport_support
      • ast: test_compile test_compiler_codegen test_dis test_fstring test_future_stmt test_peepholer test_peg_generator test_type_comments test_ucn test_unparse
      • cmd: test_cmd
      • importlib.metadata: test_importlib
      • pkgutil: test_pyrepl test_runpy
      • rlcompleter: test_pyrepl test_rlcompleter
      • trace: test_trace
    • logging: test_hashlib test_support test_urllib2net
      • hashlib: test_hmac test_unicodedata
      • multiprocessing.util: test_concurrent_futures
      • venv: test_venv
    • multiprocessing: test_fcntl test_multiprocessing_main_handling
    • symtable: test_symtable
    • tempfile: test_bz2 test_cmd_line test_cprofile test_ctypes test_doctest test_ensurepip test_faulthandler test_filecmp test_generated_cases test_importlib test_launcher test_linecache test_modulefinder test_peg_generator test_pkg test_pstats test_py_compile test_pyrepl test_selectors test_string_literals test_subprocess test_sys_settrace test_tabnanny test_termios test_threadedtempfile test_tokenize test_urllib_response test_winconsoleio test_zipapp test_zipfile test_zipfile64 test_zstd
      • ctypes.util: test_ctypes
      • urllib.request: test_sax test_urllibnet

[x] lib: cpython/Lib/struct.py
[x] test: cpython/Lib/test/test_struct.py (TODO: 7)

dependencies:

  • struct

dependent tests: (179 tests)

  • struct: test_array test_buffer test_call test_compileall test_ctypes test_deque test_fcntl test_float test_gzip test_ioctl test_itertools test_logging test_math test_memoryview test_ordered_dict test_os test_pickle test_plistlib test_socket test_ssl test_str test_struct test_sys test_tools test_venv test_wave test_xml_etree_c test_xpickle test_zipfile test_zipimport test_zoneinfo
    • base64: test_base64 test_email test_gettext test_httpservers test_smtplib test_urllib2 test_urllib2_localnet test_xmlrpc
      • http.server: test_robotparser
      • logging.handlers: test_concurrent_futures test_pkgutil
      • secrets: test_secrets
      • smtplib: test_smtpnet
      • ssl: test_asyncio test_ftplib test_httplib test_imaplib test_poplib test_urllib
      • urllib.request: test_http_cookiejar test_pathlib test_pydoc test_sax test_site test_urllib2net test_urllibnet
    • ctypes: test_android test_bytes test_code test_codecs test_ctypes test_genericalias test_io test_ntpath
      • platform: test__locale test__osx_support test_asyncio test_baseexception test_builtin test_cmath test_mimetypes test_platform test_posix test_regrtest test_shutil test_strptime test_sysconfig test_time test_winreg test_wsgiref
      • webbrowser: test_webbrowser
    • dbm: test_dbm test_dbm_dumb test_dbm_sqlite3 test_shelve
    • gettext:
      • argparse: test_argparse
      • getopt: test_getopt
      • optparse: test_decimal test_optparse
    • gzip: test_fileinput test_tarfile
    • multiprocessing: test_asyncio test_concurrent_futures test_multiprocessing_main_handling test_re
      • concurrent.futures.process: test_concurrent_futures
    • pickle: test_annotationlib test_ast test_bool test_bz2 test_collections test_configparser test_coroutines test_csv test_defaultdict test_descr test_dict test_dictviews test_email test_enum test_enumerate test_exceptions test_fractions test_functools test_generators test_http_cookies test_importlib test_inspect test_ipaddress test_iter test_list test_lzma test_memoryio test_minidom test_opcache test_operator test_picklebuffer test_pickletools test_positional_only_arg test_random test_range test_set test_slice test_statistics test_string test_structseq test_super test_trace test_tuple test_turtle test_type_aliases test_type_params test_types test_typing test_unittest test_uuid test_xml_dom_minicompat test_xml_etree test_zipfile test_zlib test_zoneinfo
      • tracemalloc: test_tracemalloc
    • tarfile:
      • shutil: test_embed test_filecmp test_glob test_importlib test_largefile test_launcher test_modulefinder test_peg_generator test_py_compile test_reprlib test_string_literals test_subprocess test_support test_tempfile test_traceback test_unicode_file
    • zipfile: test_pdb test_zipapp test_zipfile test_zipfile64 test_zipimport_support
      • importlib.metadata: test_importlib
    • zipimport: test_cmd_line_script test_importlib
      • pkgutil: test_pyrepl test_runpy

[ ] lib: cpython/Lib/unittest
[x] test: cpython/Lib/test/test_unittest (TODO: 12)

dependencies:

  • unittest (native: _io, _log, async_case, builtins, case, loader, main, os.path, result, runner, signals, suite, sys, time, unittest.util, util)
    • warnings (native: _contextvars, _thread, _warnings, builtins, sys)
    • _colorize, annotationlib, argparse, asyncio, collections, contextlib, contextvars, dataclasses, difflib, fnmatch, functools, inspect, io, logging, os, pkgutil, pprint, re, signal, threading, traceback, types, weakref

dependent tests: (408 tests)

  • unittest: regrtestdata test___all__ test__colorize test__locale test__opcode test__osx_support test_abc test_abstract_numbers test_android test_annotationlib test_apple test_argparse test_array test_asdl_parser test_ast test_asyncgen test_asyncio test_atexit test_audit test_augassign test_base64 test_baseexception test_bdb test_bigaddrspace test_bigmem test_binascii test_binop test_bisect test_bool test_buffer test_bufio test_builtin test_bytes test_bz2 test_c_locale_coercion test_calendar test_call test_charmapcodec test_class test_clinic test_cmath test_cmd test_cmd_line test_cmd_line_script test_code test_code_module test_codeccallbacks test_codecencodings_cn test_codecencodings_hk test_codecencodings_iso2022 test_codecencodings_jp test_codecencodings_kr test_codecencodings_tw test_codecmaps_cn test_codecmaps_hk test_codecmaps_jp test_codecmaps_kr test_codecmaps_tw test_codecs test_codeop test_collections test_colorsys test_compare test_compile test_compileall test_complex test_concurrent_futures test_configparser test_contains test_context test_contextlib test_contextlib_async test_copy test_copyreg test_coroutines test_cprofile test_csv test_ctypes test_datetime test_dbm test_dbm_dumb test_dbm_sqlite3 test_decimal test_decorators test_defaultdict test_deque test_descr test_descrtut test_devpoll test_dict test_dictcomps test_dictviews test_difflib test_dis test_doctest test_doctest2 test_docxmlrpc test_dtrace test_dummy_thread test_dummy_threading test_dynamic test_dynamicclassattribute test_eintr test_email test_embed test_ensurepip test_enum test_enumerate test_eof test_epoll test_errno test_except_star test_exception_group test_exception_hierarchy test_exception_variations test_exceptions test_extcall test_external_inspection test_faulthandler test_fcntl test_file test_file_eintr test_filecmp test_fileinput test_fileio test_fileutils test_finalization test_float test_flufl test_fnmatch test_fork1 test_format test_fractions test_frame test_frozen test_fstring test_ftplib test_funcattrs test_functools test_future_stmt test_gc test_generated_cases test_generator_stop test_generators test_genericalias test_genericclass test_genericpath test_genexps test_getopt test_getpass test_gettext test_glob test_global test_grammar test_graphlib test_grp test_gzip test_hash test_hashlib test_heapq test_hmac test_html test_htmlparser test_http_cookiejar test_http_cookies test_httplib test_httpservers test_idle test_imaplib test_importlib test_index test_inspect test_int test_int_literal test_io test_ioctl test_ipaddress test_isinstance test_iter test_iterlen test_itertools test_json test_keyword test_keywordonlyarg test_kqueue test_largefile test_launcher test_linecache test_list test_listcomps test_locale test_logging test_long test_longexp test_lzma test_mailbox test_marshal test_math test_math_property test_memoryio test_memoryview test_metaclass test_mimetypes test_minidom test_mmap test_modulefinder test_monitoring test_msvcrt test_multibytecodec test_multiprocessing_fork test_multiprocessing_forkserver test_multiprocessing_main_handling test_multiprocessing_spawn test_named_expressions test_netrc test_ntpath test_nturl2path test_numeric_tower test_opcache test_opcodes test_openpty test_operator test_optimizer test_optparse test_ordered_dict test_os test_osx_env test_pathlib test_patma test_pdb test_peepholer test_peg_generator test_pep646_syntax test_perfmaps test_pickle test_picklebuffer test_pickletools test_pkg test_pkgutil test_platform test_plistlib test_poll test_popen test_poplib test_positional_only_arg test_posix test_posixpath test_pow test_pprint test_print test_profile test_property test_pstats test_pty test_pulldom test_pwd test_py_compile test_pyclbr test_pydoc test_pyexpat test_pyrepl test_queue test_quopri test_raise test_random test_range test_re test_regrtest test_repl test_reprlib test_resource test_richcmp test_rlcompleter test_robotparser test_runpy test_sax test_sched test_scope test_script_helper test_secrets test_select test_selectors test_set test_setcomps test_shelve test_shlex test_shutil test_signal test_site test_slice test_smtplib test_smtpnet test_socket test_socketserver test_sort test_sqlite3 test_ssl test_stable_abi_ctypes test_stat test_statistics test_str test_strftime test_string test_string_literals test_stringprep test_strptime test_strtod test_struct test_structseq test_subclassinit test_subprocess test_sundry test_super test_support test_symtable test_syntax test_sys test_sys_setprofile test_sys_settrace test_sysconfig test_syslog test_tabnanny test_tarfile test_tempfile test_termios test_textwrap test_thread test_thread_local_bytecode test_threadedtempfile test_threading test_threading_local test_threadsignals test_time test_timeit test_timeout test_tokenize test_tomllib test_tools test_trace test_traceback test_tracemalloc test_tstring test_tty test_tuple test_turtle test_type_aliases test_type_annotations test_type_cache test_type_comments test_type_params test_typechecks test_types test_typing test_ucn test_unary test_unicode_file test_unicode_file_functions test_unicode_identifiers test_unicodedata test_unittest test_univnewlines test_unpack test_unpack_ex test_unparse test_urllib test_urllib2 test_urllib2_localnet test_urllib2net test_urllib_response test_urllibnet test_urlparse test_userdict test_userlist test_userstring test_utf8_mode test_utf8source test_uuid test_venv test_wait3 test_wait4 test_wave test_weakref test_weakset test_webbrowser test_winapi test_winconsoleio test_winreg test_winsound test_with test_wmi test_wsgiref test_xml_dom_minicompat test_xml_dom_xmlbuilder test_xml_etree test_xml_etree_c test_xmlrpc test_xpickle test_xxlimited test_xxtestfuzz test_yield_from test_zipapp test_zipfile test_zipfile64 test_zipimport test_zipimport_support test_zlib test_zoneinfo test_zstd

[x] lib: cpython/Lib/csv.py
[x] test: cpython/Lib/test/test_csv.py (TODO: 22)

dependencies:

  • csv

dependent tests: (4 tests)

  • csv: test_csv test_genericalias
    • importlib.metadata: test_importlib test_zoneinfo

[x] lib: cpython/Lib/pydoc.py
[x] lib: cpython/Lib/pydoc_data
[ ] test: cpython/Lib/test/test_pydoc (TODO: 34)

dependencies:

  • pydoc

dependent tests: (5 tests)

  • pydoc: test_enum test_pydoc
    • pdb: test_pdb
    • xmlrpc.server: test_docxmlrpc test_xmlrpc

[ ] test: cpython/Lib/test/test_bytes.py (TODO: 22)

dependencies:

dependent tests: (no tests depend on bytes)

[x] lib: cpython/Lib/bz2.py
[x] test: cpython/Lib/test/test_bz2.py (TODO: 2)

dependencies:

  • bz2

dependent tests: (101 tests)

  • bz2: test_bz2 test_codecs test_fileinput test_tarfile
    • fileinput: test_genericalias
    • shutil: test_argparse test_compileall test_ctypes test_embed test_filecmp test_glob test_httpservers test_importlib test_inspect test_largefile test_launcher test_logging test_modulefinder test_os test_peg_generator test_pkgutil test_py_compile test_reprlib test_sax test_shutil test_site test_string_literals test_subprocess test_support test_sysconfig test_tempfile test_traceback test_unicode_file test_venv test_zoneinfo
      • ctypes.util: test_ctypes
      • ensurepip: test_ensurepip
      • http.server: test_robotparser test_urllib2_localnet test_xmlrpc
      • multiprocessing.util: test_asyncio test_concurrent_futures
      • pathlib: test_ast test_dbm_sqlite3 test_importlib test_json test_pathlib test_pyrepl test_runpy test_tomllib test_tools test_unparse test_winapi test_zipapp test_zipfile test_zstd
      • tempfile: test_asyncio test_bytes test_cmd_line test_compile test_concurrent_futures test_contextlib test_cprofile test_csv test_dis test_doctest test_faulthandler test_generated_cases test_hashlib test_importlib test_linecache test_mailbox test_ntpath test_pickle test_pkg test_posix test_pstats test_pydoc test_pyrepl test_regrtest test_selectors test_socket test_sys test_sys_settrace test_tabnanny test_termios test_threadedtempfile test_tokenize test_turtle test_urllib test_urllib2 test_urllib_response test_winconsoleio test_zipfile test_zipfile64
      • webbrowser: test_webbrowser
      • zipapp: test_pdb
      • zipfile: test_zipfile test_zipimport test_zipimport_support
    • zipfile:
      • importlib.metadata: test_importlib

[x] lib: cpython/Lib/sqlite3
[x] test: cpython/Lib/test/test_sqlite3 (TODO: 81)

dependencies:

  • sqlite3

dependent tests: (2 tests)

  • sqlite3: test_dbm_sqlite3 test_sqlite3

[ ] test: cpython/Lib/test/test_memoryview.py (TODO: 9)

dependencies:

dependent tests: (no tests depend on memoryview)

[x] lib: cpython/Lib/io.py
[x] lib: cpython/Lib/_pyio.py
[ ] test: cpython/Lib/test/test_io.py (TODO: 13)
[x] test: cpython/Lib/test/test_bufio.py
[x] test: cpython/Lib/test/test_fileio.py (TODO: 1)
[ ] test: cpython/Lib/test/test_memoryio.py (TODO: 25)

dependencies:

  • io

dependent tests: (108 tests)

  • io: test__colorize test_android test_argparse test_ast test_asyncio test_base64 test_buffer test_bufio test_builtin test_bz2 test_calendar test_cmd test_cmd_line_script test_codecs test_compile test_compileall test_compiler_assemble test_concurrent_futures test_configparser test_contextlib test_csv test_dbm_dumb test_descr test_dis test_email test_enum test_file test_fileinput test_fileio test_ftplib test_generated_cases test_getpass test_gzip test_hashlib test_http_cookiejar test_httplib test_httpservers test_importlib test_inspect test_io test_json test_largefile test_logging test_lzma test_mailbox test_marshal test_memoryio test_memoryview test_mimetypes test_minidom test_multibytecodec test_optparse test_pathlib test_pdb test_peg_generator test_pickle test_pickletools test_platform test_plistlib test_pprint test_print test_profile test_pstats test_pty test_pulldom test_pydoc test_pyexpat test_pyrepl test_quopri test_regrtest test_robotparser test_sax test_shlex test_shutil test_site test_smtplib test_socket test_socketserver test_subprocess test_support test_sys test_tarfile test_tempfile test_threadedtempfile test_timeit test_tokenize test_traceback test_types test_typing test_unittest test_univnewlines test_urllib test_urllib2 test_uuid test_wave test_webbrowser test_winconsoleio test_wsgiref test_xml_dom_xmlbuilder test_xml_etree test_xml_etree_c test_xmlrpc test_xpickle test_zipapp test_zipfile test_zipimport test_zoneinfo test_zstd

[x] test: cpython/Lib/test/test_thread.py (TODO: 4)
[x] test: cpython/Lib/test/test_thread_local_bytecode.py
[x] test: cpython/Lib/test/test_threadsignals.py

dependencies:

dependent tests: (14 tests)
- [ ] concurrent.futures: test_asyncio test_compileall test_concurrent_futures test_context test_genericalias test_inspect test_struct test_wmi
- [x] asyncio: test_asyncio test_external_inspection test_logging test_os test_pdb test_unittest

Legend:

  • [+] path exists in CPython
  • [x] up-to-date, [ ] outdated

@moreal moreal self-assigned this Jul 25, 2026
@moreal
moreal marked this pull request as ready for review July 25, 2026 08:56
@moreal moreal changed the title Fix float overflow in struct packing Raise OverflowError for float overflow in struct packing Jul 25, 2026
@youknowone youknowone added the z-ca-2026 Tag to track Contribution Academy 2026 label Jul 25, 2026
@youknowone
youknowone merged commit e9f7347 into RustPython:main Jul 25, 2026
27 checks passed
youknowone pushed a commit that referenced this pull request Sep 16, 2026
Raise OverflowError when a finite f64 value overflows while being converted for the struct f format. Remove the expected-failure marker from the corresponding regression test.

Assisted-by: Codex:gpt-5
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